Contributions

Invited talks

Physics of Stars that are Sources of Stellar Feedback

Selma de Mink (U Amsterdam)

I aim to review recent advances in our insight in the lives and deaths of massive and intermediate mass stars, focussing on how this may affect their roles as sources of feedback. I will address three themes: (1) the upper stellar mass limit, (2) the role of rotation, and (3) the many effects of binary interaction and discuss how these may affect the output of ionizing radiation, mechanical, and chemical feedback.

The response of dark matter haloes to gas inflows and outflows

Aaron Dutton (New York University Abu Dhabi)

The inner structure of dark matter haloes is potentially a powerful non-linear scale probe of the nature of dark matter. In order to make a robust theoretical prediction it is essential to understand the impact of baryons on halo structure. Using the NIHAO sample of cosmological galaxy formation simulations I show that a wide range of halo responses exist, from expansion to contraction, with up to factor 10 changes in the enclosed dark matter mass at 1 per cent of the virial radius. This diversity of dark halo response is captured by a toy model consisting of cycles of adiabatic inflow (causing contraction) and impulsive gas outflow (causing expansion). I will discuss the similarities and differences between the halo response from groups using different hydro codes and sub-grid models for star formation and feedback: NIHAO (gasoline) / FIRE (gizmo) / EAGLE (gadget3) / ILLUSTRIS (arepo). For Milky Way mass galaxies the halo response seems largely independent of the subgrid models provided a realistic amount of stars is formed. For dwarf galaxies the results are sensitive to the subgrid model, with some codes predicting no change, while others predicting strong expansion to dark matter cores. I will discuss the likely source of these differences, and observational ways to distinguish between different sub-grid models.

The Physics of AGN-driven Galactic Winds

Claude-André Faucher-Giguère (Northwestern University)

Over the past decade, observations have revealed AGN feedback in action in the form of energetic, wide-angle, galaxy-scale outflows powered by luminous quasars. These outflows are observed at essentially all wavelengths, ranging from the radio to the optical to X-rays, and have raised a number of important theoretical puzzles. For example, the outflows can carry a momentum over an order of magnitude in excess of the AGN radiative output, and a large fraction of the outflowing mass is observed in cold, dense molecular gas moving at highly supersonic velocities up to ~1,000 km/s. I will discuss analytic and numerical models aiming to explain the acceleration and observational properties of AGN-driven galactic winds. Time-permitting, I will also summarize on-going efforts to model supermassive black hole growth and feedback in galaxy evolution.

Understanding the fountain-corona interaction

Filippo Fraternali (U Kapteyn)

Strong feedback in cosmological simulations appears to solve several classical problems in galaxy formation but is it the only way to do it? In this talk, I discuss the importance of the circulation produced by a mild galactic fountain and the consequent mixing between disc and the coronal gas. This mixing not only promotes gas condensation and accretion but also solves the local angular momentum problem, i.e. the difference between the angular momentum distributions between pre-galactic gas and present-day discs. I discuss the observational evidence based on detailed observations of local galaxies and end with some considerations about galaxy evolution that incorporate the fountain-corona interaction.

Effect of AGN feedback seen in IFU studies

Bernd Husemann (Max-Planck-Institute for Astronomy)

Integral field spectroscopy became a powerful and popular tool to trace ionized gas outflows across the host galaxies for luminous AGN. I am discussing the evidence for kpc-scale AGN-driven outflows that are thought to be the "smoking gun" of AGN feedback affecting their entire host galaxies. Converting the observed outflow properties into physical quantities, that can be compared with simulations, represents an additional challenge to understand AGN feedback. In this context I will present recent results from IFU surveys, such as the Close AGN Reference survey (CARS), and also highlight future prospects.

Feedback in star forming regions

Laura Lopez (Ohio State)

TBD

Observational Outflows, Loops and Superbubbles

Naomi McClure-Griffiths (Australian National University)

Galaxies are not closed box systems. Their evolution is impacted by gas accreted via inflow, gas lost from the disk via large-scale outflows and gas circulation via the halo. Many simulations of galaxy formation and evolution have highlighted the importance of feedback in reproducing the observable Universe. In this talk I will present an overview of observational evidence for superbubbles and outflows within the Milky Way and other nearby galaxies. Formed from the stellar winds and supernovae of up to hundreds of massive stars, these large-scale features dominate the observed structure of neutral hydrogen within the many galaxies. Superbubbles which grow as large as the gas layer can burst to create galactic outflows, which can circulate hot, enriched gas within a galaxy’s halo and out of its gravitational potential to enrich the surrounding intergalactic medium. The Milky Way and Magellanic system have many spectacular examples of gaseous outflows, which we are able to study with physical resolution unmatched anywhere else in the Universe. In this talk I will give an overview of how superbubbles develop and break out to form galactic outflows. I will describe how atomic hydrogen emission data is helping us to probe the outflow of the Milky Way’s nuclear wind and outflows from the Small Magellanic Cloud.

AGN jets as possible feedback mechanism

Raffaella Morganti (ASTRON and Kapteyn Institute (NL))

Radio jets have been known, since long time, to drive outflows of warm gas. More recently, also a more massive component of cold gas has been found associated with jet-driven outflows. It is therefore not surprising that radio jets are considered as one of the possible feedback mechanisms. The effect of radio jets is now studied and quantified both using high spatial-resolution observations and new numerical simulations. The latter are providing increasingly accurate predictions that start to be compared with the results from the observations. I will present some of the recent results tracing jet-driven outflows using various phases of the gas and, in particular, using the cold component (neutral atomic and molecular). Thanks to the high spatial resolution, these observations can trace the location and the properties of the outflows and the impact they may have on the host galaxy. I will present the results obtained for radio jets covering a range of radio power (proxy for the jet power) and galactic environment. The first results of the comparison with the simulations will also be presented and future perspectives will be discussed.

Magnetic fields and cosmic rays in galaxy formation

Rüdiger Pakmor (HITS/MPA)

Magnetic fields and cosmic rays are both crucial components to understand the evolution of galaxies. However, due to the complex interplay with other physical processes in galaxies their full impact on galaxy formation can only be understood with numerical simulations. Here I will present our most recent results on the evolution of magnetic fields in galaxies and show how any magnetic seed field is quickly amplified by a turbulent dynamo at high redshift. However, it only reaches equipartition at low redshift after the galaxy has formed a disk and ordered its magnetic field. Moreover, I will show results from recent galaxy simulations that also include cosmic rays and their anisotropic transport along magnetic field lines, which leads to cosmic ray driven outflows from the galaxy.

The macro- and micro-physics of thermal conduction in AGN-cluster feedback

Christopher Reynolds (University of Cambridge)

Cooling core clusters of galaxies continue to serve as important laboratories for understanding AGN feedback in massive systems. Multi-waveband observations reveal the interactions between the hot intracluster medium (ICM) and the relativistic jets produced by the AGN in the central brightest cluster galaxy. Yet there are still basic uncertainties about the physical processes underlying the AGN feedback loop, uncertainties that directly affect extrapolations of models to high redshift. Here I focus on one aspect of the problem - the role and physics of thermal conduction in the ICM. I will discuss models in which thermal conduction can both directly heat cluster cores, can be the mechanism for thermalizing AGN injected energy, and can modify the thermal instability that produces cold gas which feeds the AGN. The ICM is a weakly collisional high-beta plasma, and so the basic physics of thermal conduction is non-trivial. I will present particle-in-cell models of conduction in ICM-like systems, demonstrating the crucial role of kinetic instabilities.

Cosmic reionisation and galaxy feedback with SPHINX

Joakim Rosdahl (Centre de Recherche Astrophysique de Lyon)

I will present results from the SPHINX suite of cosmological radiation-hydrodynamical simulations of the first billion years, which capture the escape of ionising radiation through the ISM of thousands of galaxies and the collective contribution of this escaping radiation to reionisation. My focus will be on the effect of local and non-local radiation on the early suppression of galaxy growth. I will also show how supernova explosions regulate the escape of ionising radiation from galaxies and argue how we may therefore perhaps use the reionisation history as an additional observational probe of feedback and star formation physics in galaxies.

Resolving Galactic-Scale Feedback and Gas Accretion with SDSS-IV/MaNGA

Kate Rubin (San Diego State University)

Large spectroscopic surveys have now demonstrated that galactic outflows are ubiquitous among actively star-forming systems from the local universe to z>1. However, the morphology and spatially-resolved kinematics of these gas flows remain poorly constrained. I will present an analysis of absorption line profiles tracing cool gas motions in spatially-resolved spectroscopy of ~1000 galaxies at z~0.03 observed as part of the SDSS-IV/MaNGA survey. I will describe the constraints these measurements place on the relationship between local star formation activity and outflow kinematics over ~1-2 kpc spatial scales, and on the frequency and cross section of cool gas accretion onto nearby, star-forming systems.

Feedback and Feeding: The Physical Conditions and Kinematics of Gas within the High-Redshift CGM

Gwen Rudie (Carnegie Institution for Science)

I will discuss results from the Keck Baryonic Structure Survey (KBSS), a unique spectroscopic survey designed to explore both the physical properties of high-redshift galaxies and the connection between these galaxies and their surrounding intergalactic baryons. The KBSS is optimized to trace the cosmic peak of star formation (z~2-3), combining high-resolution spectra of 15 hyperluminous QSOs with densely-sampled galaxy redshift surveys surrounding each QSO sightline. I will present new detailed studies of metal-enriched absorbers in the CGM of KBSS galaxies including measurements of CIV and SiIV absorption within 1.5 Mpc as well as detailed analysis of absorbers within the viral radius of high-redshift galaxies which show the influence of galaxies on their surroundings.

Accounting for the effect of radiation in galaxy simulations

Laura V. Sales (UC Riverside)

TBD

Gas flows out and into galaxies

Joop Schaye (Leiden Observatory)

TBD

AGN feedback in clusters

Debora Sijacki (Cambridge UK)

TBD

Cosmological insights into Feedback

Volker Springel (MPA)

Reconciling observed galaxy properties with predictions of cold dark matter cosmologies requires the presence of strong, scale-dependent feedback processes. I review some of the corresponding evidences and discuss the possible impact of feedback on cosmological constraints. I also discuss in turn some of the constraints on feedback arising from cosmology.

An Observational Perspective on Galactic Winds and the Circumgalactic Medium

Sylvain Veilleux (University of Maryland)

The fate of baryons in a galaxy is governed by the complex interplay between gas entering the galaxy through mergers and accretion flows, star formation within the galaxy, and gas outflowing from the galaxy. All gas phases and dust are participating in this cosmic ballet. This presentation will focus on the impact of starburst- and quasar-driven outflows on galaxy evolution. The results from recent multi-wavelength surveys of gas and dust flows out of nearby and distant galaxies will be reviewed and interpreted in the context of these galaxies' ecosystems. New constraints on the circumgalactic medium in distant galaxies will also be presented to constrain the impact of starburst- and AGN-driven processes in the past. This review will conclude with a discussion of some of the open issues and promising new avenues of research to address them.

Simulting galaxy formation in CDM and SIDM

Mark Vogelsberger (MIT)

In the first part of my talk I will present a brief overview of the Illustris and IllustrisTNG simulations demonstrating that these simulations - based on the CDM paradigm - successfully describe the large-scale distribution of galaxies. In the second part of my talk I will then present simulation results that go beyond the CDM model by exploring self-interacting dark matter as a potential CDM alternative. I will demonstrate how the properties of galactic halos are altered once dark matter particles are allowed to scatter with each other.

Cosmic ray feedback in galaxies and clusters

Karen Yang (U Maryland)

TBD

Structure formation with non-gravitational dark matter interactions

Jesús Zavala Franco (University of Iceland)

The standard structure formation model is based on the Cold Dark Matter (CDM) hypothesis where non-gravitational dark matter interactions are irrelevant for the formation and evolution of galaxies. Surprisingly, current observations allow for significant departures from the CDM hypothesis, which could potentially leave signatures of the dark matter particle nature in the properties of galaxies. In this talk, I will describe some of these 'alternative' dark matter hypotheses and their connection to particle physics models from the perspective of a generalized theory of structure formation.

Contributed talks

Probing the gas fuelling and outflows in nearby AGN with ALMA

Anelise Audibert (Observatoire de Paris)

Feeding and feedback in active galactic nuclei (AGN) play a very important role to gain a proper understanding of galaxy formation and evolution. The interaction between activity mechanisms in the nucleus and their influence in the host galaxy are crucial for the feedback and gas fuelling of the black hole (BH). Winds and outflows produced by the AGN can eject or heat the gas, terminate the star formation and through the lack of fuel for accretion, quench the black hole activity. Recent discoveries of massive molecular outflows have been promoting the idea that winds may be major actors in sweeping the gas out of galaxies, in agreement with theoretical predictions of AGN-driven winds models. AGN are fuelled by accretion of material onto the SMBH and the gas component can form stars on its way to the central engine. By studying the molecular gas in galaxy disks we want to understand: (i) how the star formation and nuclear activity are fuelled and what are the timescales involved, since both process rely on a common cold gas supply, but in different timescales (∼10^5 yr for BH growth and ∼10^{7−9} yr for star formation)? (ii) what are the mechanisms driving gas from the disk towards the nucleus, removing its large angular momentum and forming large non-axisymmetric perturbations? Our goal is to probe these phenomena by probing the gas inside the central kpc in nearby AGN. This has recently been possible due to the unique ALMA spatial resolution and sensitivity. We present a study of the morphology and kinematics of the cold dense gas in a modest sample of nearby Seyfert/LINER nuclei at the unprecedented spatial resolution of 0.06-0.09” (3-10 pc), part of a new ALMA follow-up of the NUGA (NUclei of GAlaxies) program. NUGA is a high-resolution (0.5-1”) CO survey of 25 low luminosity AGN performed with the IRAM PdBI that has revealed smoking gun evidence of gas funnelling into the nucleus in 1/3rd of the sample. This result suggested that galaxies may be alternating periods of fuelling and starvation, and might be found in a feeding phase at 100pc scales only 1/3rd of the time.

The importance of feedback in the formation of realistic galactic dwarf galaxy populations

Tobias Buck (MPIA)

In this talk I will present a set of new very high-resolution hydrodynamical simulations of Milky Way mass galaxies and their dwarf galaxy inventory. These simulations result in satellite mass functions, abundance matching relations and mass metallicity relations which are extremely well in agreement with observations of the Local Group. I will discuss how feedback is able to reconcile the properties of simulated dwarf galaxies with observations and alleviate long standing issues of LCDM. E.g. the missing satellites problem does not occur in these simulations due to the fact that many dwarf galaxy mass dark matter haloes completely fail to form stars. I will further present a new implementation of a stellar energetical and chemical feedback scheme using the combined impact of three different channels - supernova type II, Ia and AGB stars based on the chempy package (Rybizki et al. 2017). Our implementation enables us to track the chemical enrichment by different sources and to follow the enrichment of various elements currently measured by large scale galactic surveys like GALAH, 4MOST or APOGEE2. Our new simulations provide a new framework to understand the detailed enrichment history of the Milky Way.

Black Hole Feedback in Dwarf Galaxies

Gabriela Canalizo (University of California, Riverside)

Black holes are believed to populate the centers of all galaxies with mass comparable to the Milky Way and above. For such massive galaxies, the interaction of black holes and their accretion disks with the surrounding gas leads to the formation of powerful gas outflows that heat up and may eventually escape the galaxy. Such feedback may have a strong effect in the star formation rate and the overall growth and evolution of massive galaxies. However, in low mass dwarfs, the most common type of galaxies in the Universe, the presence of massive black holes is largely unknown and their effects on star formation histories are currently ignored. In this talk, I will present the discovery and measurement of extended gas outflows most likely powered by black holes in five dwarf galaxies hosting actively accreting black holes (aka AGN). The measured outflow velocities are enough to escape the galaxy and their surrounding dark matter halo, leaving behind a gas-depleted and poorly star-forming galaxy. We find clear evidence for this ongoing star formation suppression which is driven mostly by the active galactic nuclei. Galaxy formation models must therefore be able to account not only for the formation and growth of black holes in the centers of dwarf galaxies but should also be revised to include black holes as important --and perhaps dominant-- sources of feedback in low mass galaxies.

AGN feedback: jet populations, environments, and what we're learning from LOFAR surveys

Judith Croston (The Open University)

New radio surveys provide an opportunity to pin down the demographics of the radio-loud AGN population to low luminosities and to high redshifts, and across the full range of AGN life stages. If we want to exploit these population statistics to obtain a physical understanding of jet evolution and energetic impact as a function of galaxy and large-scale environmental properties, we need to know how observable radio properties can be converted to jet powers and lifetimes, and we need to understand the links between jet populations, host galaxies and large-scale environment. The LOFAR HETDEX 150-MHz survey provides the deepest view over a wide area (424 deg^2) of any existing radio survey, with sufficient resolution to measure jet sizes and morphologies, and is providing the most detailed information to date about when, where and how radio-loud AGN feedback is taking place at z<1. I will present highlights of this ongoing work, including investigation of the role of low-luminosity "galaxy-scale" jets at low redshifts, investigation of the links between AGN properties and large-scale environment, and modelling of the energetic impact of the low-frequency selected radio-loud AGN population.

Properties and Scaling Relations of Ionized Gas Outflows at z~1-3

Rebecca Davies (Max Planck Institute for Extraterrestrial Physics)

Outflows are ubiquitous at the peak epoch of star formation (z~1-3), and likely play an important role in shaping the growth and evolution of galaxies. Near-IR integral field spectroscopy is a powerful tool to investigate the physical properties of galactic winds at this epoch because it enables us to kinematically disentangle them from gravitational motions, and to map the launch sites, extent, and geometry of outflows. I will present results from our SINFONI and KMOS outflow studies at z~1-3, focusing on properties and scaling relations of SF-driven outflows resolved on ~1-2 kpc scales. We find that the outflow velocity and mass loading factor correlate with the local star formation surface density, and that up to ~30% of the outflowing ionized gas may be ejected from the galaxy disks. I will explore whether there is a minimum local star formation surface density required to drive outflows, and discuss the results in the context of our other IFU outflow studies from the SINS/zC-SINF and KMOS^3D surveys (including AGN driven outflows).

CR propagation and magnetic fields in galactic halos: observational evidence of CR driven galactic winds (?)

Ralf-Jürgen Dettmar (Ruhr-University Bochum)

Recent numerical models of the multiphase ISM underline the importance of cosmic rays and magnetic fields for the physics of the ISM in star-forming disc galaxies. We will present new observational evidence from radio-continuum polarization studies of edge-on galaxies. This includes results from the CHANG-ES (Continuum HAlos in Nearby Galaxies - an EVLA Survey; PI J. Irwin) project which has observed 35 edge-on galaxies with the Karl G. Jansky Very Large Array (JVLA) in two frequency bands (L- and C-band) and in three array configurations (D, C, B). This survey benefits significantly from the new multi-channel capability of the upgraded facility. From the total power maps, a "mean" radio-continuum halo has been derived and the polarization information provides information on the magnetic field structure in the halos. The findings will be discussed in the context of CR driven galactic winds. In this context we will also briefly discuss most recent results from LOFAR observations of edge-on galaxies.

Understanding the emergence of Low Surface Brightness Galaxies

Arianna di Cintio (IAC (istituto astrofisica de canarias) Tenerife - Spain)

LSBs are extremely dark matter dominated, faint objects hardly distinguishable from the night sky. In the last decade it has became clear that large numbers of LSB galaxies exist, opening a new window on galaxy evolution and formation. How do such diffuse galaxies form and evolve? How are they linked to their dark matter haloes, and how do they fit within the current cosmological model of galaxy formation? I will make use of state-of-the-art, sophisticate hydrodynamical cosmological simulations to try to answer these questions.

The Role of Multi-channel Stellar Feedback in Galactic Chemical Evolution

Andrew Emerick (Columbia University)

Galactic chemical evolution is driven by the complicated interplay of gas accretion, galaxy mergers, star formation, stellar feedback, mixing and turbulence in the ISM, and galactic outflows. Stellar feedback is fundamental in this evolution. How metals -- ejected in stellar winds and supernovae -- mix with a multi-phase ISM and couple to galactic winds depends sensitively on feedback physics that is poorly understood. Improving our theoretical understanding of both stellar feedback and galactic chemical evolution is becoming increasingly important as number and quality of observations of stellar and gas phase abundances in nearby galaxies continues to grow. We use high resolution, hydrodynamics simulations of isolated, low mass dwarf galaxies to better understand the complex relationship between feedback and galactic chemical evolution. By following stars as individual star particles, we can model both stellar feedback and stellar yields in unprecedented detail. Our star-by-star feedback model includes stellar winds from massive stars and AGB stars, photoelectric heating, stellar ionizing radiation followed through a ray-tracing radiative transfer method, core collapse supernovae, and Type Ia supernovae. We have used these simulations to explore differences in how metals with different nucleosynthetic origins mix within the ISM and couple to galactic winds. I will summarize these results to-date and present ongoing work in understanding the role each component of our multi-channel stellar feedback model plays in driving the chemical evolution of galaxies.

Testing Feedback Regulated Star Formation in Turbulent, Clumpy Disk Galaxies

Deanne Fisher (Swinburne University)

I will present results using the DYNAMO sample of nearby galaxies. These extremely rare galaxies are very well matched in gas fraction (fgas~20-80%), kinematics (rotating disks with velocity dispersions ranging 20-100 km/s), structure (exponential disks) and morphology (clumpy star formation) to high-z main-sequence galaxies, however DYNAMO are located at z=0.1. We therefore use DYNAMO galaxies as laboratories to study the processes inside galaxies in the dominate mode of star formation in the Universe, and carry out targeted, complementary studies to large surveys at high redshift. In this talk I will report on results from our programs with HST, Keck and NOEMA for DYNAMO galaxies that are aimed at testing feedback regulated models of star formation. We have discovered of an inverse relationship between gas velocity dispersion and molecular gas depletion time. This correlation is directly predicted by theories of feedback regulated star formation. I will show that predictions of models in which turbulence is driven by gravity are not consistent with our data. I will also use the relationship between pressure and SFR surface density to further test models of feedback regulated star formation. I will show that while the observed relationship between pressure and SFR surface density is qualitatively similar to predictions from models of feedback regulated star formation, there are however large quantitative differences between matching data and current theoretical models. I will discuss the implication of these differences on the amount of momentum injected into the ISM from star formation feedback.

Raining on Galaxies and Black Holes: Unifying the Micro and Macro Properties of AGN Feedback and Feeding

Massimo Gaspari (Princeton University)

Feeding and feedback tied to supermassive black holes (SMBHs) play central role in the cosmic evolution of galaxies, groups, and clusters of galaxies. The self-regulated active galactic nucleus (AGN) cycle is matter of intense debate. I review key results of our numerical campaign to unveil how SMBHs are tightly coupled to the multiphase gaseous halos, linking the inner gravitational radius to the large Mpc scale and vice versa. Massively parallel MHD simulations show the turbulent plasma halo radiatively cools via a top-down multiphase condensation rain of warm filaments and molecular clouds. The multiphase precipitation inherits the hot halo kinematics and thermodynamics, ultimately establishing a 'cosmic weather'. In the nuclear region, the recurrent collisions between the clouds and filaments promote angular momentum cancellation and boost the SMBH accretion rate through a mechanism known as chaotic cold accretion (CCA). The CCA rapid variability triggers powerful AGN outflows, which quench the macro cooling flow and star formation, while preserving the atmospheres of galaxies, groups, and clusters in global thermal equilibrium throughout cosmic time. I highlight the key imprints of AGN feedback and feeding, such as bubbles, shocks, turbulence, and condensed structures, with a critical eye toward observational concordance, including the X-ray plasma, optical filaments, and radio molecular clouds.

Cooler and smoother – the impact of cosmic rays on the phase structure of galactic outflows

Philipp Girichidis (AIP Potsdam)

Cosmic rays are an important energy component in the interstellar medium with energy densities comparable to the thermal and magnetic one but with different transport and cooling processes compared to the thermal gas. CRs diffuse or stream relative to the gas and thus transport a significant fraction of the energy away from their production sites at supernova (SN) remnants throughout the interstellar medium and into the galactic halo. Using three-dimensional magneto-hydrodynamical simulations including CRs as a relativistic interacting fluid, we investigate their dynamical and chemical impact on the interstellar medium and molecular clouds. We find that only 5-20 percent of the CR energy injected by SNe is lost via hadronic interactions. The remaining CRs can thicken the galactic disk and delay the formation of molecular clouds. In addition, they drive strong, smooth and stready outflows with mass loading factors or order unity. The outflows mainly consist of warm atomic gas. In addition, we extend the classical advection-diffusion approximation for CRs with a spectral method in order to cover the large energy range and the accurate energy dependent interactions. Our novel, non-dissipative implementation allows us to span the regime from MeV to TeV and accurately account for CR losses, pressure and diffusion in every computational cell. Besides the dynamics, this spectral distribution is key to connecting the CR physics to observable quantities like synchrotron and gamma-ray emission of galaxies.

How gas-flows and feedback shape Milky Way-sized galaxies in the Auriga cosmological simulations

Robert Grand (HITS, ZAH (Heidelberg))

We present insights into how feedback and gas-flows shape the evolution of Milky Way mass galaxies from the Auriga suite of high resolution cosmological zoom simulations, ran with a comprehensive galaxy formation model including stellar and AGN feedback and magnetic fields. These simulations produce stellar and HI gas disc properties in broad agreement with observations. We discuss the role of feedback and turbulent gas accretion in shaping the evolution of the star-forming gas and stellar distribution: at high redshift, higher stellar feedback and turbulent gas accretion ensures that gas discs are thicker and more irregular than at low redshift, in good agreement with the ‘upside-down’ formation scenario and ‘disc settling’ seen in star forming galaxies in redshift ranges from z~0 to 3. We demonstrate that this feedback model predicts quantifiable feedback-driven galactic fountain flows that recycle metal-enriched gas back into the ISM, causing a continuous increase in gas-phase metallicity over time, in contrast to the assumptions of many analytic chemical evolution models. Furthermore, we highlight that the strength of AGN feedback varies widely among the simulations, and in some cases is an important mechanism to suppress star formation in the central galaxy, particularly for compact discs.

Linking Star Clusters to Galaxies with Feedback

Kathryn Grasha (Australian National University)

The impact of spiral structures and stellar feedback on the interstellar medium (ISM) has fundamental implications for our understanding of star formation in the present-day universe. The feedback from star clusters play a critical role in the self-regulation of star formation. Star clusters thus provide a key missing piece in a predictive theory of star formation through linking the scales of individual stars and star clusters to the scales of entire galaxies. I will present results on combing resolved star clusters in nearby galaxies with molecular gas to constrain the onset of star formation and ionized gas at spatial scares comparable to star clusters and GMCs to probe feedback processes and how variations in star formation modes affect the structure of the ISM. The science presented in this talk represents potentially informs on the evolution of star clusters over cosmic time and early phases of galaxy evolution, allowing us to draw connections between young, massive star clusters and their role as possible progenitors of globular clusters.

Fantastic AGN outflows and where to find them: The SUPER survey

Darshan Kakkad (European Southern Observatory)

Numerous observational and theoretical studies over the past decade have put a strong fundamental ground on the existence of Active Galactic Nuclei (AGN) feedback in the form of outflows. Radiative feedback from AGNs are believed to have a significant impact on the global properties of the galaxies, especially at redshift of 1<z<3 where the black hole as well as the star formation activity were at their maximum. This motivated the initiation of the sinfoni Survey for Unveiling the Physics and Effect of Radiative feedback (SUPER), an on-going ESO large program with SINFONI/VLT IFU with AO-assisted observations at 2.1<z<2.5. SUPER survey is designed to have an unbiased look at the impact of ionized outflows, traced by OIII5007 line, on short time scale star formation rate, traced by the narrow Halpha line at a resolution of ~1kpc for z~2. We explore a wide range in bolometric luminosities and Eddington ratios spanning ~4 orders of magnitude among the targets of the survey. In this talk, I will present the results from these high resolution SINFONI-IFU observations which shed light on a plethora of outflow morphologies at high redshift along with the evidence of the existence of correlations between the properties of the outflow and the central black hole. We will also discuss the impact of such outflows on the current and long term star formation of the host galaxies and consequently if these outflows are indeed capable of quenching star formation.

Impact of radiation fields in Galaxies

Rahul Kannan (Harvard-Smithsonian Center for Astrophysics)

Radiation fields are thought to play an important role in regulating star formation in Galaxies. A variety of physical mechanisms such as photoheating, radiation pressure and trapped IR radiation have been invoked to disperse the stellar birth clouds and even drive large scale outflows. However, the modelling of these processes have so far been necessarily crude due to the lack of an efficient radiation hydrodynamics (RHD) implementation. I will present a series of high resolution RHD simulations using Arepo-RT, that self consistently model these radiative processes in order to quantify the importance of each of them in a variety of environments.

Supernova driven galactic winds and fountains with self-consistently regulated ISM and star formation rates

Changgoo Kim (Princeton/CCA)

Galactic scale outflows, gas blown away from galactic disks, play a key role in galaxy evolution. I will present characteristics of galactic outflows driven by supernova (SN) feedback utilizing our high-resolution, local galactic disk simulation suite, TIGRESS (Three-phase ISM in Galaxies Resolving Evolution with Star formation and Supernova feedback). In our numerical implementation, star formation and SN feedback are self-consistently treated and well resolved in the multiphase, turbulent, magnetized interstellar medium (ISM). Bursts of star formation produce spatially and temporally correlated SNe that drive strong outflows, consisting of hot winds and warm fountains. The hot gas moving away from the galactic disk has mass and energy fluxes nearly constant, implying that the hot wind from our local Cartesian box can provide the mean mass and energy loading factors robustly. For the warm gas, the mean outward mass flux is decreasing as a function of distance from the midplane. The warm flows created and launched by expanding hot superbubbles within a few disk scale height eventually fall back as fountains. The velocity distribution at launching better represents warm outflows than a single mass loading factor. Finally, I will emphasize the importance of self-consistent modeling of the spatiotemporal correlation of SNe with the ISM in light of both regulating ISM properties and launching winds.

The Local Volume Mapper in SDSS-V: Connecting Stellar Feedback with the ISM in the Milky Way and Local Group

Kathryn Kreckel (MPIA)

Connecting studies across the pc (sub-GMC) and kpc (galaxy-wide) scales is fundamental to understanding the physics governing star formation, the structure and energetics of the ISM, the baryon cycle, and ultimately, the evolution of galaxies. The LVM in SDSS-V will take the first step towards the “spectral panopticon”, a full spectroscopic image of the sky, providing optical IFU data-cubes to resolve, e.g., SF structures, GMCs, H II regions and young stellar clusters. The LVM will cover the bulk of the MW disk at 0.1-1 pc resolution, the Magellanic Clouds at 10 pc resolution, M31 & M33 at 20 pc resolution, and Local Volume galaxies out to a distance of 8 Mpc at ∼ 25-100 pc resolution, in total about 1 steradian of sky. Stellar spectroscopy with accurate typing and abundances from previous APOGEE observations and from SDSS-V itself as well as resolved stellar photometry and CMDs (in the Magellanic Clouds, M31 & M33) will allow us to connect the structures in the ISM to the radiation field and to individual sources of feedback. The wide area covered by the LVM will sample a large variety of SF regions caught at different stages of their life cycles, as probed by the age estimated from resolved stellar data. I will present key science themes that will be addressed by LVM, including the connection between ionized gas, star formation, and feedback on multiple physical scales; the extraction of maximum information from the union of resolved and integrated stellar population data; and the geometric structure of the ionized and dusty ISM to better understand chemical abundances and enrichment.

Survival of molecular gas in a stellar feedback-driven outflow witnessed with the MUSE TIMER project and ALMA

Ryan Leaman (MPIA)

Stellar feedback plays a significant role in modulating star formation, redistributing metals, and shaping the baryonic structure of galaxies - however, the efficiency of its energy deposition to the interstellar medium is often difficult to constrain observationally. As part of our MUSE TIMER survey, we have identified a molecular gas and dust shell in ALMA and HST images, at the leading edge of an energetic outflow from the nuclear ring of the galaxy NGC 3351. The total energy budget of this stellar feedback event is comparable to low luminosity AGN, and we show via analytic and numerical modeling of the feedback processes, that SNe and stellar radiation pressure can drive the ionized and molecular gas out of the nuclear ring, in accordance with our observed MUSE kinematics. We test several scenarios for the survival/formation of the cold gas in the outflow, including in-situ condensation and cooling. Interestingly, the geometry of the molecular gas shell and emission line diagnostics are consistent with a scenario where magnetic field lines aided survival of the dusty ISM as it was initially launched from the ring by stellar feedback. The required magnetic field strengths are in agreement with indirect observational constraints as well as analytic disk equilibrium models. This system's unique feedback driven morphology can hopefully serve as a useful litmus test for subgrid prescriptions in hydrodynamical galaxy simulations.

Bridging Small-scale Supernovae Feedback to Hot Circumgalactic Medium

Miao Li (CCA, Flatiron Institute)

Supernovae(SNe)-driven outflows remove mass and metals from galaxies and prevent new gas from coming in, but how important are they? The answer depends on (i) how much mass/energy/metals outflows actually carry, and (ii) how the outflows interact with cosmic inflows. Solving the first question requires a parsec-resolution for multiphase ISM, whereas the second a sufficiently large simulation domain. Achieving both is unfeasible for Milky Way-size galaxies, therefore we adopt a two-step approach. First, we simulate kpc-patches of ISM with parsec-resolution, and quantify the loading efficiencies of mass, energy, and metals of SNe-driven outflows for a wide range of star formation (SF) intensities. We find the hot outflows carry the majority of the energy and metals. Second, we run galactic-scale simulations while adopting a sub-grid model of hot outflows which is directly obtained from the small-box simulations. We study the large-scale evolution of the outflows in the circum-galactic medium (CGM), and investigate how SF activity, galaxy potentials, and existing halo gas change the impact of outflows. In particular, I will discuss the systematic comparison of the X-ray observations of the CGM around spiral galaxies to our simulations, and how multiple lines of constraints help to illustrate the nature of SNe feedback.

The HESTIA Project

Noam Libeskind (Leibniz Institute for Astrophysics Potsdam)

The HESTIA (High resolution Environmental Simulations of the immediate area) project is an endeavor to simulate the Local Group and the local volume. The simulations employ the AREPO magneto-hydrodynamical cosmological code, combined with the Auriga galaxy formation model. In order to properly simulate the local volume we use initial conditions constrained by observations of the peculiar velocity field compiled by the cosmic flows survey. The result is a high resolution simulation of the local group, with two galaxies that match a litany of observations of the real Local Group, embedded in cosmographic environment which closely resembles our own.

Physics at High Angular resolution in Nearby Galaxies: A MUSE and ALMA view of the outflow in NGC1672

Rebecca McElroy (Max Planck Institute for Astronomy)

The PHANGs collaboration (Physics at High ANgular resolution in Nearby GalaxieS) aims to examine the connection between the small-scale physics of gas and star formation and galaxy evolution. This will be achieved using an unprecedented data-set which combines high spatial resolution MUSE and ALMA data for a sample of 19 nearby galaxies (at a distance <25Mpc) from two ESO large programs. Here we introduce the PHANGs survey and highlight early science including observations of NGC1672, which is a known low-luminosity Seyfert galaxy that hosts an outflow. By combining optical emission line diagnostics and kinematics from our MUSE mosaic with ALMA CO observations of the molecular gas we are able to further characterise the outflow. Our detailed high angular resolution (1"=50pc) and spatial coverage data then allow us to investigate whether the outflow is having a significant impact on the galaxy as a whole and whether AGN feedback is important in this galaxy.

Self-regulated growth of the most vigorously, gravitationally lensed, star-forming galaxies at high redshift

Nicole Nesvadba (Institut d'Astrophysique Spatiale, CNRS)

Strongly gravitationally lensed galaxies are veritable gems for our understanding of high-redshift galaxy evolution, allowing us to study dust, gas, and star formation even in the most intense starbursts on scales of individual star-forming regions. On these scales, below one to few 100 pc in the source plane, kpc-scale rotational support no longer dominates, and star formation is regulated by the local gas and stellar mass surface densities and energy injection from turbulence and winds driven by star formation and AGN. I will report on our on-going multi-wavelength follow-up of gas, dust, and star formation in a small set of the brightest high-z galaxies on the sub-mm sky, "Planck's Dusty GEMS", with VLT, HST, ALMA, IRAM, and SMA, amongst others. The GEMS host some of the most intensely star-forming clumps known in high-z galaxies, without evidence of powerful AGN, and their gas kinematics show that star formation may well be self-limiting through turbulence, in broad agreement with analytical models. Star formation in individual clumps may be regulated by outflows with high mass-loading factors, although the observed gas velocities suggest that much of the gas may remain trapped within the host galaxy, and be available for future star formation. If time permits, I will also discuss the first direct estimate (from gravitational lensing) of a bottom-heavy stellar initial mass function in a massive lensing galaxy in the early Universe, at z=1.5.

Warm Molecular Gas and Dust in Active Galaxies

Andreea Petric (Institute for Astronomy University of Hawaii / Canada France Hawaii Telescope)

Observations of the dynamics of stars and gas in the nuclear regions of nearby galaxies suggest that the overwhelming majority of spheroidal galaxies in the local Universe contain massive black-holes (BH) and that, with some important caveats, the masses of those central BH correlate with the velocity dispersion of the stars in the spheroid and the bulge luminosities. Much research has been dedicated to understanding the mechanisms responsible for such a fundamental - perhaps causal - relation. An accurate census of the basic properties of the interstellar medium (ISM) in galaxies with accreting super-massive black holes at their centers, i.e. galaxies that host active galactic nuclei (AGN), is pertinent to those investigations because molecular gas fuels both black hole growth and star-formation. Nearby, Luminous Infrared Galaxies (LIRGs) in which the IR emission originates mostly from the AGN have about 100 K higher H2 mass-averaged excitation temperatures than LIRGs in which the IR emission originates mostly from star formation. Between 10 and 15% of LIRGs have H2 emission lines are sufficiently broad to be resolved or partially resolved by the high resolution modules of Spitzer's Infrared Spectrograph (IRS) allowing us to estimate the kinetic energy in the warm molecular component.Those sources tend to be mergers and contain AGN and we find that the kinetic energy in the H2 gas correlates with the H2 to IR luminosity ratio. We also analyzed 2200 Spitzer archive mid-infrared spectra of active galaxies to determine if and how accreting, super-massive black holes at the center of galaxies impact the interstellar medium of their hosts and found a 200K difference between the excitation temperatures of the higher pure rotational molecular hydrogen transitions in AGN dominated and non-AGN dominated spectra. We find a statistically significant positive correlation between excess molecular hydrogen emission and the relative contribution of the AGN to the IR emission and interpret this as evidence that AGN impact the ISM of their host galaxies.

Cosmic rays in galaxy formation: acceleration, transport, feedback

Christoph Pfrommer (AIP)

Understanding the physics of galaxy formation is an outstanding problem in modern astrophysics. Recent cosmological simulations have demonstrated that feedback by star formation, supernovae and active galactic nuclei appears to be critical in obtaining realistic disk galaxies and to slow down star formation to the small observed rates. However the particular physical processes underlying these feedback processes still remain elusive. In particular, these simulations neglected magnetic fields and relativistic particle populations (so-called cosmic rays). Those are known to provide a pressure support comparable to the thermal gas in our Galaxy and couple dynamically and thermally to the gas, which seriously questions their neglect. After introducing the underlying physical concepts, I will present our recent efforts to model cosmic ray physics in galaxy formation. I will demonstrate that cosmic rays play a decisive role on all scales relevant for the formation of galaxies, from individual supernova remnants up to scales relevant for entire galaxies.

The Feedback Acting on Baryons in Large-scale Environments (FABLE) simulations of galaxy, group and cluster formation

Ewald Puchwein (IoA & KICC, University of Cambridge)

We present a new suite of high-resolution cosmological hydrodynamical simulations of galaxies, groups and clusters. The simulations use the AREPO moving-mesh code with a set of physical models for galaxy formation based on the successful Illustris simulation, but with updated AGN and supernovae feedback models. This allows us to simultaneously reproduce the observed redshift evolution of the galaxy stellar mass function together with the stellar and gas mass fractions of local groups and clusters across a wide range of halo masses. Focusing on the properties of groups and clusters, we find very good agreement with a range of observed scaling relations, including the X-ray luminosity--total mass and gas mass relations as well as the total mass--temperature and Sunyaev-Zel'dovich flux--mass relations. Careful comparison of our results with scaling relations based on X-ray hydrostatic masses as opposed to weak lensing-derived masses reveals some discrepancies, which hint towards a non-negligible X-ray mass bias in observed cluster samples. We further show that radial profiles of density, pressure and temperature of the simulated intracluster medium are in very good agreement with observations, in particular for r > 0.3 r500. In the innermost regions however we find too large entropy cores, which indicates that a more sophisticated modelling of the physics of AGN feedback may be required to accurately reproduce the observed populations of cool-core and non-cool-core clusters. Promising avenues to further improve the AGN feedback modelling are discussed.

Testing AGN feedback on cold molecular gas in local luminous Seyfert galaxies

David Rosario (CEA, Durham University)

The destruction and dispersal of star forming (i.e., molecular) gas is an important pathway for AGN feedback in most models of galaxy formation. I will report on a carefully controlled CO spectroscopic study of a complete volume-limited set of the most luminous nearby (D < 40 Mpc) Seyfert galaxies, designed to understand whether the gas fractions and star formation efficiencies are influenced by the presence of the AGN, an essential test of AGN feedback. Despite several advances over earlier studies of this kind, we find no differences between AGN and inactive galaxies: indeed, the star formation efficiencies (SFE) in the centres of Seyferts are consistent with their larger-scale discs. Our results are observational validation of the resilience of star-forming molecular gas against the effects of AGN feedback.

Impact of super-Alfvenic streaming on cosmic ray driven galactic winds

Mateusz Ruszkowski (University of Michigan)

Galactic outflows play an important role in galaxy evolution and, despite their importance, detailed understanding of the physical mechanisms responsible for the driving of these winds is lacking. Although cosmic rays (CRs) comprise only a tiny fraction of interstellar particles by number, they carry energy comparable to that in the thermal gas. Since the characteristic cooling times of CRs can exceed the radiative cooling time of the ISM, CRs can have a significant impact on the dynamics of the galactic gas. I will discuss recent progress in 3D MHD modeling of galactic winds made by our group. I will focus on the dynamical role of CRs injected by supernovae, and specifically on the impact of CR transport along the magnetic fields. Recent results show that this microphysical process can have a significant impact on the wind launching depending on the details of the plasma physics. In the self-confinement model, CRs stream along the magnetic field lines at the Alfven speed due to scattering off self-excited Alfven waves. However, MHD turbulence stirred up by stellar feedback dissipates these confining waves, allowing CRs streaming to be super-Alfvenic. We perform 3D MHD simulations of a section of a galactic disk, including CR streaming dependent on the local environment and using a realistic model of turbulent dissipation of Alfven waves. We find that streaming does effectively become super-Alfvenic and, compared to the Aflvenic streaming case, the gas and CR distributions become more spatially extended and the heights of these distributions increase with the turbulence strength. We show that while the time-integrated mass loading factors are relatively independent of the effective transport speed, the instantaneous mass loading factors (which are directly observable) are very sensitive to local streaming physics. The instantaneous mass loading factors decrease significantly as turbulence becomes stronger. While largely an unexplored territory, CR feedback is an important process facilitating launching and efficient driving of galactic-scale winds in starburst galaxies, and remains the subject of intense research.

Feedback impact on dark matter and cosmology

Matthieu Schaller (Leiden Observatory, Leiden, Netherlands)

We use a series of simulations on different scales to analyse the impact of baryonic physics and, especially, of feedback on the dark matter distribution. This analysis based on the EAGLE, C-EAGLE and APOSLTE runs allow to draw a self-consistent picture of how feedback processes affect the dark matter on all the relevant scales. Whilst this is interesting in itself, as a prediction for cosmological probes, it can also, more interestingly, be used to put constraints on the feedback models themselves and possibly ruling out some parts of parameter space. Constraints provided by observations of cluster members (e.g. using MUSE pointings of Frontier Fields data) can already be used in this respect and already set interesting limits on the feedback behaviour.

Effect of feedback on the normalization and slope of the molecular Kennicutt-Schmidt relation

Vadim Semenov (University of Chicago)

When averaged on kiloparsec and larger scales, observed star formation rates in galaxies correlate almost linearly with the amount of molecular gas. This tight correlation is analogous to the Kennicutt-Schmidt relation and it implies that the depletion time of molecular gas has a characteristic value, ~2 Gyr, which exhibits only a small scatter and remains almost independent of molecular gas density on >kpc scales. Both the value and the universality of depletion time were long standing puzzles. Indeed, Gyr-long depletion time is substantially longer than any dynamical time scales relevant for star formation in galaxies and most popular models of star formation predict a strong dependence of depletion time on gas surface density. I will present a physical model that explains the origin of long depletion times in galaxies. Our model is based on the insights from a suite of isolated galaxy simulations and it explains the roles of feedback, local star formation, and dynamical flows of interstellar gas in shaping global star-forming properties of real and simulated galaxies. In particular, this model explains how global star formation rates in simulations self-regulate and become independent of local star formation efficiency when local efficiency is high and feedback is strong. In addition, both our model and simulation results hint to possible reasons for why depletion times of molecular gas are so universal and therefore why the molecular Kennicutt-Schmidt relation is linear. My talk will be based on published papers (Semenov, Kravtsov, Gnedin 2017 http://adsabs.harvard.edu/abs/2017ApJ...845..133S and 2018 https://arxiv.org/abs/1803.00007) as well as on new results.

A Song of Fire and Feedback: The Importance of AGN-driven Outflows in Quenching Star Formation in Massive Galaxies

Michael Tremmel (Yale University)

Using the Romulus cosmological simulations, including a zoom-in simulation of a galaxy cluster with unprecedented resolution, we show how powerful outflows driven by AGN are a crucial component to quenching galaxies from Milky Way-mass to brightest cluster galaxies. These outflows often extend to 10s kpc and, in the case of BCGs, 100 kpc or 10% R_200. The outflows can be columnated out to large radii and do not directly destroy or disrupt much of the gas in the host galaxy, but rather affect how hot halo gas cools on larger scales. This means that star formation can be regulated and even quenched while still maintaining low entropy and sub-Gyr cooling times in the core of the halo. In massive galaxies AGN feedback acts to change the entropy structure of the gas, which affects the ability of cold gas to precipitate out of the hot halo. These results also demonstrate an important success of thermal models of AGN feedback in cosmological simulations, indicating that previous shortcomings are likely due to the details of the implementation and, most importantly, limited resolution.

Enhanced turbulence and larger cold gas reservoirs in the CGM of a simulated Milky Way-mass galaxy

Freeke van de Voort (HITS & Yale)

Galaxy evolution is regulated by the inflow and outflow of gas. Studying the circumgalactic medium (CGM) can therefore help us understand how galaxies' gas reservoirs are replenished and how galactic winds alter the galaxies and their environments. It can also help test theoretical models by comparing them to available observations of the CGM. Usually simulations focus their computational effort on the galaxies themselves and the resolution decreases with decreasing density. However, there is evidence from idealized simulations that the CGM behaves very differently at high resolution. I will present a zoom-in simulation of a Milky Way-mass galaxy from the Auriga project, resimulated with fixed spatial resolution within its virial radius, resulting in a detailed view of its gaseous halo at z=0 at unprecedented (1 kpc) uniform resolution. I will discuss how this affects the physical and observable properties of the CGM, the role of feedback, the return of previously expelled gas, and the distribution of heavy elements in these simulations. I will present evidence of enhanced (inflow- and outflow-driven) turbulence and larger cold gas reservoirs.

Evidence for radiative feedback from young star clusters in the Antennae Galaxy

Peter Weilbacher (Leibniz-Institut für Astrophysik Potsdam (AIP))

Using the integral field spectroscopic capabilities of MUSE at the VLT we observed a mosaic of the "Antennae Galaxy" (NGC 4038/39), the closest major merger in progress. Instrument sensitivity allowed us to detect a large fraction of diffuse ionized gas in the system, to greater depth than possible before. We compared HII region luminosities and stellar populations of the corresponding clusters as derived from HST data. The result suggests that the young star clusters in the central Antennae provide enough Lyman-continuum radiation to explain both the HII regions and the ionization of the diffuse gas. A similar balance of stellar radiative feedback and ionized gas emission seems to hold in a quieter star-forming location at the end of the southern tidal tail. As other sources of Lyman-continuum photons (like shocks and old populations) should be present in the interacting system as well, it is hence likely that the overall system is a Lyman-continuum leaker.

Active galactic nucleus feedback in simulations

Rainer Weinberger (Harvard, CfA)

Supermassive black holes (SMBHs) are an important ingredient in modern simulations of galaxy formation. Their feedback effects have proven to be essential for reproducing key properties of massive galaxies, such as their low gas fractions, their inefficiency in forming stars and their intrinsic colours. In this talk, I will show what we can learn from modelling active galactic nucleus (AGN) feedback in state of the art simulations. First, I will discuss the IllustrisTNG simulations, a set cosmological magneto-hydrodynamical full-physics simulations of structure formation, covering a dynamic range from 300 Mpc in the largest simulation volume to few hundred pc in the highest resolution simulation. I will discuss the assumptions that go into the modelling of AGN in these large-scale simulations and show how AGN feedback acts in halos of different masses and redshifts and its consequences for the host galaxies, their evolution as well as the SMBH growth histories and associated observables. Focusing on galaxy clusters, I will show the successes and shortcomings of the modelling in IllustrisTNG and discuss how complementary high-resolution simulation of AGN feedback, in particular of AGN driven jets in more idealised environments can be used to better understand the physical nature of AGN feedback. Finally, I will give an outlook on how this combination of small- and large-scale studies can be applied also to lower mass and to high redshift galaxies to systematically study the effect of AGN driven outflows in different environments.

Reignition of Star Formation in Dwarf Galaxies

Anna Wright (Rutgers, The State University of New Jersey)

Within the Local Group, there are a number of star-forming dwarf galaxies that show evidence of a period of little to no star formation within their histories. Using a suite of high resolution cosmological simulations, we find this scenario is common for dwarf galaxies in halos less massive than 10$^{10}$ M$_\odot$ (~1 in 5 dwarfs). Star formation is typically shut off by reionization, although some galaxies are also quenched by their own supernova feedback. Importantly, these processes do not remove all of the gas from the halo. All of our galaxies maintain a hot gaseous halo of 10$^{7-8}$ M$_\odot$ in mass. This gas is later compressed through interactions with gas in the intergalactic medium to restart star formation. The source of the compressing gas is not necessarily cosmic filaments. Rather, the dwarfs interact with gas thrown off by nearby galaxies during mergers or periods of strong stellar feedback. While high ram pressure interactions of this nature lead to stripping, the encounters that cause star formation reignition are low density and/or low velocity and thus low ram pressure, and tend to result in compression of the hot gas in the halos of our dwarfs. Consequently, we find that dwarfs with reignition events in their histories tend to be more HI-rich than their counterparts for billions of years after star formation has resumed.

Posters

The Role of AGN Feedback in Quenching Star Formation in Local Central Galaxies

Nikhil Arora (Queen's University)

We study the agents that regulate the quenching of star formation in massive, central galaxies through an AGN feedback model. The Sloan Digital Sky Survey (SDSS) DR8 and a version of Munich semi-analytic model are combined to develop a new technique for identifying central galaxies in dark matter halos. This enables us to study the correlation between predicted AGN suppressed cooling of the gas and the observed fraction of quenched central galaxies in an observationally motivated parameter space. Isolated, massive galaxies are found to be more frequently passive than is predicted by the Munich model. The model predicts quenched fractions that correlate with the heating rate of gas due to AGN feedback and hence the mass of the supermassive black hole, at odds with SDSS galaxies whose quenched fraction scales with the mass of the bulge. The scatter in the predicted bulge mass - black hole mass relation for the model is also unexpectedly large and unmatched by observations. These disagreements suggest that the growth of the central black hole and the bulge mass are heavily decoupled in the model and/or that the black hole growth and AGN feedback prescriptions in the model are inadequate. Furthermore, an unrealistic strong threshold is seen in star formation as a function of SMBH mass. We suggest that the bulge mass - black hole mass relation and their growth mechanisms can be coupled through the formation of a hot gas halo around the bulge as a result of heating due to AGN feedback. This would allow for the formation of isolated, massive quenched galaxy and for the presence of a weaker cutoff in star formation as a function of SMBH mass.

Large-scale mass distribution in the IllustrisTNG simulation

Maria Celeste Artale (University of Innsbruck, Institute for Astro- and Particle Physics)

The aim of this work is to investigate the so-called missing baryon and metals problem through the analysis of the cosmological hydrodynamical simulation IllustrisTNG. For this, we explore the distribution of gas, metals, and ions in filaments, voids, and haloes as a function of time. We also study their cosmic evolution adopting four phases (hot, WHIM, condensed and diffuse). In this talk, I will present our results.

How radiation background influences the growth of dwarf galaxies.

Lucie Bakels (University of Western Australia/ ICRAR)

Dwarf galaxies provide an important testbed for our theories of galaxy formation and in particular our understanding of the influence of feedback. Using hydrodynamical galaxy formation simulations, we investigate how low-mass dark matter halos accrete gas and how the rate of accretion is influenced by the nature of the background radiation field. These provide insights into how non-local heating by compact objects might impact the present galaxy population.

Braginskii viscosity on an unstructured, moving mesh

Thomas Berlok (Postdoc, Leibniz-Institut für Astrophysik Potsdam (AIP))

We present a method for efficiently modeling Braginskii viscosity on an unstructured, moving mesh. Braginskii viscosity, i.e. anisotropic transport of momentum with respect to the direction of the magnetic field, is thought to be of prime importance for studies of the weakly collisional plasma that comprises the intracluster medium of galaxy clusters (ICM). Our new method for modeling Braginskii viscosity has been implemented in the moving mesh code Arepo and we present a number of examples in order to illustrate the modified dynamics. These include a simulation of a linearly polarized Alfvén wave which is interrupted by the firehose instability and a simulation of the evolution of the Kelvin-Helmholtz instability which is inhibited by Braginskii viscosity. An explicit update of Braginskii viscosity is associated with a severe time step constraint that scales with (\Delta x)^2 where \Delta x is the grid size. In our implementation, this restrictive time step constraint is alleviated by employing 2nd order accurate Runge-Kutta-Legendre super-time- stepping. This makes it computationally feasible to perform high resolution simulations of galaxy clusters. We envision including Braginskii viscosity in a number of future studies of Kelvin-Helmholtz unstable cold fronts in cluster mergers and the propagation of AGN generated bubbles in central cluster regions.

Anisotropic Jeans modelling of early-type galaxies out to multiple half-light radii

Nicholas Boardman (University of Utah)

Early-type galaxies (ETGs) are widely believed to represent the end-points of galaxy evolution, but the full range of mechanisms behind ETG formation remains unclear. To further our understanding of how ETGs form, we observed twelve ETGs with the Mitchell integral-field Spectrograph and obtained stellar kinematics out to multiple half-light radii. Our ETGs comprise of a mix of elliptical and lenticular galaxies, are mostly fast-rotating, and all have detectable quantities of neutral Hydrogen gas. We constructed Jeans dynamical models of the galaxies’ second velocity moments in order to constrain the galaxies’ mass distributions, intrinsic shapes and orbital anisotropies. We find our modelling to favour low dark matter fractions within our galaxies’ central effective radii, along with total mass density distributions that are close to isothermal on average. When the orbital anisotropy in our models is allowed to vary with position, we further find our models to favour non-radial anisotropies in most of our galaxies’ stellar outskirts, in agreement with simulations of ETGs with gas-rich formation histories. Our near-isothermal total density slopes are in good agreement with previous observational work, and provide important constraints on galaxy formation models.

The Fate of Supernova-Heated Gas in Star-Forming Regions of the LMC: Lessons for Galaxy Formation?

Chad Bustard (University of Wisconsin - Madison)

High resolution observations, detailed star formation histories, and growing observational evidence for local outflows make the Large Magellanic Cloud (LMC) and the LMC filament an intriguing case-study of supernovae-driven outflows and the fate of ejected gas. I will present simulations of local fountain flows in the LMC and their interaction with ram pressure. As the LMC falls into the Milky Way halo, compression along the leading edge may trigger star formation, leading to clustered supernovae and outflows. Our isolated disk simulations show lofted gas splashing back onto the LMC disk, while simulations including ram pressure serve as a proof-of-concept that ram pressure can sweep this material behind the galaxy and into the Magellanic Stream. Gas launched near the peak in star formation history of the LMC can be swept tens of kiloparsecs behind the disk by present-day, which matches well with HI observations of the LMC filament length, although the simulated column density is too low. More massive and numerous outflows may be possible with more detailed wind launching treatments; however, higher inertia gas will lengthen the timescale for this gas to be swept away by ram pressure. Overall, the Magellanic Stream, which may fall into the Milky Way, represents a nearby example of intergalactic gas transfer between dwarf and host galaxies, and the conversion of fountain flows to expelled gas has ramifications for a number of systems undergoing ram pressure stripping.

The Effect of Cosmic Rays on the Evolution and Momentum Deposition of Supernova Remnants

Damiano Caprioli (University of Chicago)

Using a semi-analytical approach based on the thin-shell approximation, we calculate the long-term evolution of supernova remnants (SNRs) while also accounting for the cosmic rays (CRs) accelerated at their blast waves. Our solution reproduces the results of state-of-the-art hydro simulations across the adiabatic and radiative stages for the gas-only case and predicts that typical CR acceleration efficiencies measured in self-consistent kinetic simulations (~10-20% ) can boost SNR momentum deposition by a factor of 3-5. This enhancement becomes more prominent in environments in which the gas experiences more severe radiative losses. This result may have a crucial impact on modeling the effect of supernova feedback on star formation and galaxy evolution.

Cosmic rays in simulations with explicit stellar feedback

Tsang Keung Chan (UCSD)

We investigate the effects of cosmic ray (CR) feedback on dwarf and MW-mass idealized galaxies that include the FIRE model for star formation and stellar feedback. We explore different propagation models, including advection, isotropic diffusion, anisotropic diffusion or streaming. We find that CRs with slow propagation mildly suppress star formation. CRs with fast diffusion or streaming can develop a significant pressure gradient against gravitational force and help drive large-scale galactic winds. Compared to SN driven winds without CRs, CR-driven winds have much lower temperature and lower initial velocities, but the mass loading factors with and without CRs are comparable.

The KBSS Survey: Using Galaxy-Galaxy Projected Pairs to Trace the Structure and Kinematics of HI on Mpc Scale at z~2

Yuguang Chen (California Institute of Technology)

We present the first results from the Keck Baryonic Structure Survey (KBSS) Galaxy Pairs project, in which we used background galaxy sightlines to probe the environment around foreground galaxies with z~2. In this work, we search for projected galaxy pairs among 3533 galaxies in 19 KBSS fields with impact parameters up to ~6pMpc. By stacking the background LRIS spectra in the rest frame of the foreground galaxies in various impact parameter bins, we are able to probe the kinematics of Lyman alpha (Lya) absorption around z~2 galaxies. To explain the observation, we construct a toy model, from which we argue that the kinematics structures are results from the outflows in the galactic halos, the inflows from the HI background, and the Hubble expansion.

The observed mass and metal outflow rates shape the mass-metallicity relation

John Chisholm (University of Geneva)

Many observed galactic properties are strongly correlated. Perhaps the tightest of these correlations is between the stellar mass and gas-phase metallicity of star-forming galaxies (the mass-metallicity relation). Theory predicts that the mass-metallicity relation arises because stars inject energy and momentum into the surrounding gas, accelerating the gas out of galaxies as a galactic outflow. Galactic outflows remove more metals from low-mass galaxies than high-mass galaxies due to their shallower gravitational potentials, creating the observed mass-metallicity relation. Here, I constrain the ionization structure and metallicity of galactic outflows using weak ultraviolet absorption lines from HST observations of seven nearby star-forming galaxies and photoionization models. These seven galaxies span a factor of 10,000 in star formation rate and stellar mass, and I explore how the energetics, mass outflow rates, and abundances of galactic outflows depend on host galaxy properties. Outflows from low-mass galaxies remove up to 20 times more mass than forms into stars at velocities above their escape velocities. The mass-loading factor increases with decreasing stellar mass: outflows dominate the consumption of gas in low-mass galaxies. The outflow metallicity does not scale with stellar mass, rather it scatters about solar metallicity. Outflows are significantly metal-enriched, compared to their interstellar metallicities. The metal-loading factor--the ratio of the rate that metals are ejected through outflows to the rate that metals are retained by star formation--suggests that outflows remove metals from low-mass galaxies 100 times more rapidly than star formation. The scaling of the metal-loading factor with stellar mass agrees with analytic prescriptions to reproduce the observed mass-metallicity relation. These observations demonstrate that galactic outflows shape one of the tightest scaling relations in observational astronomy.

Feedback-driven superbubbles in nearby dwarf galaxies: the energy balance and triggering of star formation

Oleg Egorov (Sternberg Astronomical Institute of Lomonosov Moscow State University)

Stellar feedback is important process regulating the ISM morphology and kinematics. Cumulative action of the winds and ionizing radiation from massive stars with a following supernova explosions blow out superbubbles having sizes from a few pc to several kpc. This process is especially important in dwarf irregular galaxies, which thick gaseous disk and a lack of the density waves allow such structures to live longer and grow to a larger sizes than in spiral galaxies. Here we present the results of ongoing survey of the ionized gas morphology and kinematics conducting with a scanning Fabry-Perot interferometer at the Russian 6-m telescope. Currently we have obtained data for 15 galaxies, mostly from M81 group. We have identified several tens of expanding structures in the ISM of observed galaxies. Thanks to a proximity of these galaxies, we were able to identify individual OB stars by the archival HST data and to compare directly the energetics of the observed superbubbles and their driving sources. Using also the available data in HI 21 cm and FUV we compare the ionized and neutral gas kinematics in the observed galaxies and analyze the propagation of star formation across them. We have found that at least in several galaxies the collision of the giant kpc-sized supershells plays important role in triggering of a new burst of star formation.

Search of the gas inflows and outflows in the void galaxies

Evgeniya Egorova (Sternberg Astronomical Institute, Moscow State University (Moscow, Russia); Special Astrophysical Observatory of Russian Academy of Science (Nizhnij Arkhyz, Russia))

We study the ionised gas kinematics in the Halpha emission line with the scanning Fabry-Perot interferometer at the Russian 6-m telescope. We are searching for the regions with a high velocity dispersion and with significant velocity deviations from the tilted-ring model of pure circular rotation. Such features could indicate the infall of external gas or the feedback from the massive stars and supernovae in the star-forming regions. Using the additional spectral observations and the multiwavelength archival data we may distinguish between the different sources of accreted gas in the case of inflows and study the feedback process in the case of outflows.

Dynamics of AGN bubbles and cosmic rays in cool core clusters

Kristian Ehlert (Leibniz-Institut für Astrophysik Potsdam (AIP))

Feedback processes by active galactic nuclei (AGN) in the center of clusters appear responsible for preventing large-scale cooling flows and impeding star formation. However, the detailed heating mechanism remains uncertain. A promising idea relies on the dissipation of Alfvén waves that are generated by streaming cosmic rays (CRs). We use 3D magnetohydrodynamical simulations with the Arepo code to study the evolution of self-consistently inflated bubbles that are filled by CRs in a turbulent cluster atmosphere. We find that a single injection event recovers the necessary CR distribution and heating rate postulated for the CR model. In addition, we verify that magnetic fields drape around the bubble, which initially confines the CRs and suppresses the formation of interface instabilities. As the bubble rises buoyantly, we notice a significant amplification of radial magnetic filaments in the wake of the bubble, which allows CRs to be conducted from the bubble to the cooling intracluster medium. Varying jet parameters, we obtain a rich and diverse set of jet and bubble morphologies ranging from FRI to FRII jets and identify jet energy as the leading order parameter. In contrast, the jet luminosity is primarily responsible for setting the Mach numbers of the shocks that are driven into the intracluster medium and produce FRI jet morphologies that are consistent with observations.

Photometric properties of galaxies in the HS47.5-22 field

Alexandra Grokhovskaya (SAO RAS)

We explore the photometric properties of galaxies by drawing a sample of about 40000 galaxies in the 2 sq. degrees HS47.5-22 field (the coordinates of the center 09h50m00s + 47d35m00s). The sample is limited by the threshold of magnitude RAB = 23m. The observations were carried out with the 1-meter Schmidt telescope of the Byurakan Astrophysical Observatory (Armenia) in 12 medium-band (FWHM = 250 A) and 5 broadband (SDSS) filters. We constructed the Spectral Energy Distribution (SED) for all galaxies in the field by accurate photometry of object images in each filter. Using medium band SEDs we obtained the spectral types and photometric redshifts of galaxies (with remarkable accuracy on the order of 0.002 for early types galaxies and 0.005 for the others). Based on the obtained results we reconstructed the three dimensional large-scale distribution of galaxies with the frame of the early types galaxies which describe the structure reliably. Main goal of our investigation is study of the connection between star formation rate in galaxies and their position in large scale structure. First steps in this study will be showed in our contribution.

How productive is the SMC at TeV energies?

Maria Haupt (DESY)

The Small Magellanic Cloud (SMC) is well studied in many wavelengths and there are still many studies ongoing. But what is about the very-high-energy regime? From observations of the Fermi LAT experiment we know that the SMC has a diffuse gamma-ray emission component in the GeV energy regime and H.E.S.S. observations of the Large Magellanic Cloud showed that there are sources in the LMC that can accelerate particles to even higher energies of several TeV. Beside the LMC, the SMC is the only galaxy for which individual sources and large-scale emission can be resolved by current ground-based Cherenkov telescopes. Therefore, they are the ideal targets to study the connection of the Galactic population of very-high-energy gamma-ray sources and the “integrated” diffuse emission seen from e.g. other star-forming galaxies. Based on observations with comparable energy flux sensitivities of the SMC, the LMC and the Milky Way, comparisons of TeV source populations in the three systems and their efficiencies of converting energy into TeV gamma-rays lead to a better understanding of the important mechanisms that control the cosmic ray feedback. In this contribution I will discuss potential gamma-ray source populations including supernova remnants, pulsars, pulsar wind nebulae, high-mass X-ray binaries and star forming regions and compare them to those of the Milky Way and known sources in the LMC. Finally, I will discuss similarities and differences of particle acceleration processes in the three systems and the importance of the environment regarding the efficiency of cosmic-ray feedback in the galaxy.

PhEW: Physically Evolved Winds in Cosmological Simulations

Shuiyao Huang (Dept. Astronomy, UMass Amherst)

QSO absorption line studies of the CGM using HST COS are the best direct way to study the accretion and galactic wind processes that are thought to dominate galaxy formation. Hydrodynamic simulations are crucial to interpret and understand these observations. Unfortunately, simulations are sensitive to wind implementations. Interactions at wind/halo gas interfaces in the CGM occur on scales that are much below the resolution of any current or near future galaxy formation simulation. We propose to implement a new wind algorithm that explicitly models the "subgrid physics" in the wind-halo gas interaction analytically within a simulation, using the simulation to provide the physical characteristics that will inform the interaction. Unavoidably, this introduces a few free parameters but we can restrict them by matching observed galaxy. Previous simulations using a more standard wind model approaches reproduced many observed properties of galaxies and metal-line absorption, but our new wind implementation will allow us to tie empirical successes, and failures, more securely to the underlying wind physics, both the ejection (mass-loading factors and ejection speeds) and the interaction between the wind and gaseous halo, and allow us to identify absorption line features with specific physical processes.

A galaxy at z=9.1 and its star formation history

Akio Inoue (Osaka Sangyo University)

Using ALMA, we have successfully detected the [OIII] 88 micron emission line from a galaxy at 7.4-sigma, yielding a redshift of z=9.1096. This precise redshift allows us to attribute the observed red Spitzer [3.6]-[4.5] color to a Balmer break in the stellar continuum instead of strong optical emission lines. The Balmer break requires an inactive phase of star formation in the galaxy of >100 Myr between the estimated formation epoch at z~15 and the observed epoch at z=9.11. The intense feedback from the first burst episode may produce such an inactive phase. The first burst can also make a large cosmological ionized bubble surrounding the galaxy and may explain a marginal Lyman-alpha emission line found with VLT. The observed blueshift relative to the [OIII] line may suggest the presence of inflowing gas which spread out once and fell back to the galaxy.

Study of X-ray Irradiated Inter Stellar Medium in Circinus Galaxy Nucleus at 10 pc resolutoin with Chandra and ALMA

Taiki Kawamuro (NAOJ)

We study properties of X-ray irradiated inter stellar media (ISM) in the Circinus galaxy nucleus based on Chandra and ALMA high spatial resolution (~ 1 arcsec or 20 pc at 4.2 Mpc) X-ray and mm/submm data. We identify X-ray irradiated dense gas by creating maps of iron line emitting regions based on ~300 ksec Chandra/ACIS data. They are spatially compared with molecular emission observed with ALMA. Physical parameters such as hydrogen molecular gas densities (n_H2) are also constrained by fitting the observed molecular line ratios to those predicted from a non-LTE model. A noticeable finding is possible molecular destruction within an iron line bright area, and the molecules seem to preferably locate along its outer region. This is clearly seen through dense gas tracing HCO+(4--3) emission, which likely associates with the nuclear structure. This suggests that the atomic gas rather than the molecular one tends to dominate the inner region. For the physical interpretation, we quantitatively discuss the X-ray dominated region (XDR) model. A key parameter of an effective ionization parameter (xi_eff = L_X/(R^2 n_H2 N_H^1.1)) is constrained at R = 60 pc, corresponding to the outer limb of the iron line bright region, given the X-ray luminosity (L_X) and the attenuating column density (N_H) for the incident X-ray. The estimated values of xi_eff are consistent with a predicted atomic-to-molecular hydrogen transition boundary (Maloney et al. 1996). Thus, we suggest that the X-ray radiation is dissociating molecules within the Circinus galaxy nucleus (< 60 pc). Moreover, given a positive correlation of the molecular gas rather than the atomic one surface density with the starformation rate, our result supports that the X-ray radiation is able to suppress the starformation.

Dispersal of Giant Molecular Clouds by UV Radiation Feedback from Massive Stars

Jeong-Gyu Kim (Princeton University)

Most star formation in local galaxies takes place in giant molecular clouds (GMCs). While it is widely believed that UV radiation feedback from massive stars can destroy natal GMCs by exciting H II regions and driving their expansion, quantitative understanding of how this actually occurs remains incomplete. To investigate the role of photoionization and radiation pressure in regulating star formation efficiency (SFE) and lifetime of GMCs, we perform a suite of radiation hydrodynamic simulations of cloud dispersal allowing for self-consistent star formation as well as the inhomogeneous density distribution arising from turbulence. Our parameter study shows that the net SFE increases primarily with the initial surface density of the cloud and that clouds are destroyed within ~2-10 Myr after the onset of feedback. The importance of radiation pressure (relative to photoionization) increases with the initial surface density. The dominant mass loss mechanism is photoevaporation, although dynamical ejection also contributes significantly in low-mass and/or high surface density clouds. We show that the photoevaporation rate depends only on the ionizing photon rate and cloud size with a scaling relation consistent with theoretical expectations. However, the outflow momentum generated by thermal and radiation pressure forces is nearly an order of magnitude lower than the prediction based on spherical expansion, due to escape of radiation and momentum cancellation. We will discuss the astronomical implication of our findings.

Stellar cluster formation in simulations of interacting dwarf galaxies

Natalia Lahén (University of Helsinki)

We study the formation of stellar clusters in simulations of interacting gas-rich dwarf galaxies with feedback from individual stellar mass particles. Our simulations are run with SPHGal (Hu et al. 2017), a modified version of GADGET-3 with non-equilibrium cooling and chemistry, interstellar radiation fields and shielding, star formation, and stellar feedback at a baryonic mass resolution of a few solar masses. Mergers of gas-rich dwarf galaxies are ideal sites for the formation of long-lived bound stellar structures. Our aim is to follow the formation of massive stellar clusters, which may be progenitors to globular clusters in subsequent accretion into massive galaxies. We present the key properties of the cluster population during and after the merger, while comparing to the observed stellar clusters of e.g. LMC and SMC.

The MOSDEF Survey: The Prevalence and Properties of Galaxy-wide AGN-driven Outflows at z~2

Gene Leung (UC San Diego)

We present new results from the MOSFIRE Deep Evolution Field (MOSDEF) survey on galaxy-wide AGN-driven outflows at z~2. The sample consists of nearly 200 X-ray, IR, and/or optically selected AGNs at 1.37 < z < 3.8. The AGNs have bolometric luminosities of 10^44 - 10^46 erg/s, including both quasars and moderate-luminosity AGNs. We detect blueshifted, ionized gas outflows in the H-beta, [O III], H-alpha, and/or [N II] emission lines of 20% of the AGNs. The outflow velocities span ~300 to 1800 km/s. Nearly 50% of the outflows are spatially extended on similar scales to the host galaxies, with spatial extents of 2.5 - 11.0 kpc. Line ratio diagnostics indicate that the outflowing gas is photoionized by the AGN. The outflows have mass-loading factors of the order of unity, suggesting that they help regulate star formation in their host galaxies, though they may be insufficient to fully quench it. We will discuss correlations between outflow properties and AGN and host galaxy properties, which constrain the physics behind these outflows.

Mapping Lyman continuum escape in Tol1247-232

Genoveva Micheva (AIP)

Low redshift, spatially resolved Lyman continuum (LyC) emitters allow us to clarify the processes for LyC escape from these starburst galaxies. We use Hubble Space Telescope (HST) WFC3 and ACS imaging of the confirmed low-redshift LyC emitter Tol 1247−232 to study the ionization structure of the gas and its relation to the ionizing star clusters. We perform ionization parameter mapping (IPM) using [O III]λλ4959, 5007 and [O II]λ3727 imaging as the high- and low-ionization tracers, revealing broad, large-scale, optically thin regions originating from the center, and reaching the outskirts of the galaxy, consistent with LyC escape. We carry out stellar population synthesis modeling of the 26 brightest clusters using our HST photometry. Our analysis suggests that, similar to other candidate LyC emitters, a two-stage starburst has taken place in this galaxy, with a 12 Myr old, massive, central cluster likely having pre-cleared regions in and around the center, and the second generation of 2 − 4 Myr old clusters dominating the current ionization, including some escape from the galaxy.

The Outflows in SUNBIRD LIRGS

Moses Mogotsi (South African Astronomical Observatory)

Nearby starburst galaxies and LIRGs are great laboratories to study star formation and feedback. Through them we can study how intense star formation and galaxy interactions affect the interstellar medium and morphology of galaxies. High star formation rates can power strong winds and outflows which can lead to quenching and morphological changes, which are important aspects of galaxy evolution. We performed an optical spectroscopic study of nearby LIRGs that are part of the SUNBIRD sample with the South African Large Telescope. The H-alpha and Na D rotation curves of 28 of these LIRGS were derived to determine the kinematics of the ionized and neutral gas. We use the differences between the H-alpha and Na D kinematics and perform profile analysis to identify outflows and to study their properties. These are being used to determine the relationship between multi-phase outflows and star formation in conjunction with molecular gas studies of these galaxies. I will present the methods we use to identify outflows and how their properties relate to star formation in this sample of galaxies. I will then connect these results of this analysis to what we are finding in the IFU and HERACLES molecular gas studies.

Kinematics and ionization properties of gas outflows in nearby galaxies viewed with Fabry-Perot interferometry

Alexei Moiseev (Special Astrophysical Observatory, Russian Academy of Sciences)

Even in the era of modern integral-field spectrographs, the Fabry-Perot interferometer (FPI) still provides a unique combination of large field of view, high spectral resolution, and detailed image sampling that are important to study the stellar feedback influence on the ionized ISM among nearby star-forming galaxies. We present the first results of our research of the known wind outflow candidates (NGC 1569, NGC 3077, etc.) based on combination of the high-order FPI to study the gas kinematics and velocity dispersion mapping, and the low-order tunable-filter FPI for imaging in the characteristic emission lines. Observations were carried out at the SAO RAS 6-m telescope and SAI MSU 2.5-m telescope. The relation between the ionized gas velocity dispersion and forbidden to Balmer lines ratio is used for diagnostics of shock fronts in the outflow matter. Also we announced the first observations of ionized-gas cones and AGN outflow taken with MaNGaL (Mapper of Narrow Galaxy Lines) - a new tunable-filter imager designed for observations with moderate-sized telescopes.

UVIT imaging of WLM : Demographics of star forming regions in the nearby dwarf irregular galaxy

Chayan Mondal (Indian Institute of Astrophysics, India.)

We present a study of star forming regions and its demographics in the nearby dwarf irregular galaxy WLM using the Ultra-Violet Imaging Telescope (UVIT) multi band observations. UVIT , a space telescope onboard ASTROSAT satellite, is capable of imaging simultaneously in far-UV and near-UV bands with a circular field of view of 28 arcmin. It has multiple photometric filters in each UV channel with an angular resolution of $\sim$1.5 arcsec. This telescope is well suited to study recent star formation in nearby galaxies, here we present a study of the isolated galaxy WLM. The galaxy, located at a distance 995 kpc, is observed in three UVIT filters F148W (1250-1750 $\AA{}$), N245M (2148-2710 $\AA{}$) and N263M (2461-2845 $\AA{}$). We study the UV emission profile of WLM in both FUV and NUV bands and find that the UV emission is extended atleast up to 1.7 kpc, with the NUV emission more extended than the FUV. We create UV color maps ((F148W$-$N245M) and (F148W$-$N263M)) to study the temperature morphology of young stellar complexes with the help of kurucz stellar model. We identify several complexes with temperature T $>$ 17500 K which are likely to be the OB associations present in the galaxy. The detected high temperature regions also show good spatial correlation with the H$\alpha$ emitting regions, H$~$I distribution and HST detected hot stars. The hot star forming regions are found to be clumpy in nature and show a hierarchical structure (hottest core enveloped by relatively low temperature regions), with sizes in the range of 4 - 50 pc, with a large number having sizes $<$ 10 pc. The overall sizes of OB associations in WLM, detected through UVIT, are found to be quite similar to those in IC 1613 (nearby dwarf irregular), but smaller than those in M33 (nearby spiral) and the Milky Way. The south western part of the galaxy shows many hot star forming regions, high level H$\alpha$ emission and low column density of H$~$I which altogether signify a vigorous recent star formation. A few isolated star forming regions were identified and treated as point sources, for which we derive the mass using starburst99 SSP model. WLM is likely to have a large fraction of young low mass clusters with mass M $< 10^3 M_{\odot}$, in agreement with the size and mass of the CO clouds. We estimate the star formation rate of WLM to be 0.008 $M_{\odot}/yr$, which is similar to the average value measured for nearby dwarf irregular galaxies.

Using hot gas velocity measurements to probe AGN feedback in massive galaxies

Anna Ogorzalek (Stanford/KIPAC)

The velocity structure of the X-ray emitting atmospheres of massive galaxies and galaxy cluster cores remains a key open question in our understanding of AGN feedback and galaxy evolution. By combining resonant scattering and direct line broadening techniques, applied to deep XMM-Newton Reflection Grating Spectrometer observations, we have obtained unprecedented measurements of the turbulent velocities in the cores of 13 nearby giant elliptical galaxies, allowing us to explore, for the first time, the typical nature of hot gas motions in these objects. In addition, we have successfully applied our technique to the Hitomi observation of the Perseus Cluster. In this talk I, will introduce our measurements with both XMM-Newton and Hitomi, and discuss their implications for the physics of AGN feedback. I will also discuss the potential for resonant scattering measurements in the coming era of high resolution X-ray spectroscopy with the X-ray Astronomy Recovery Mission and ATHENA.

Understanding wind-mode feedback in the X-ray brightest AGN

Anna Ogorzalek (Stanford/KIPAC)

A crucial missing piece in our understanding of AGN feedback is the physics of accretion-driven black hole winds. These fast, highly ionized, energetic winds, which can dramatically impact their host galaxies, imprint their physical states in absorption features seen in the X-ray band. In order to robustly map the ionization, velocity and density structure of these powerful outflows, as well as their duty cycles, high signal-to-noise, high spectral resolution data are required, spanning multiple epochs; and where such data are available, their modelling can present many challenges. In this talk I will introduce an improved approach to modelling deep X-ray spectra for nearby AGN, wherein the ionizing spectrum and absorption by winds are treated self-consistently within an MCMC analysis. This provides substantial improvements in our ability to explore parameter space and to recover the covariance between the emission and absorption parameters. For the first time, we are able to perform robust model selection, allowing us to establish how many wind components are required by the data. By way of example, we apply our approach to a new, deep observation of the Seyfert-1 galaxy NGC 4051 (700 ks of Chandra HETG), where we successfully map multiple absorbing components moving at ~few 1000 km/s, and, with the use of archival data, track their temporal evolution. Future work will extend the analysis to a population study of the physical structure and duty cycles of disk winds in local AGN. This study will serve as a pathfinder for future high spectral resolution X-ray missions, including XARM, Arcus, and ATHENA.

Molecular outflows in young radio galaxies

Tom Oosterloo (Netherlands Institute for Radio Astronomy (ASTRON))

Our view of the physical conditions of the gas in the central regions of AGN has been enriched by the discovery of fast, massive outflows of molecular gas in AGN. These outflows can be driven by radiation from the AGN, but also by the plasma jets ejected by the AGN. These outflows impact on the growth on the central supermassive black hole as well as on the star formation of the host galaxy. Much of the physics of these outflows, and their impact on the evolution of the host galaxy, is still not well understood. Better understanding these outflows, and quantifying their impact, requires tracing their location and deriving their physical conditions (density, mass, mass outflow rate and kinetic energy etc.). We will present recent ALMA observations which have allowed to study the details of the molecular outflows in two radio galaxies where young radio jets play a key role in shaping the surrounding gaseous medium. Data on multiple molecular transitions allow us to derive the physical conditions in different regions of the outflows. We will describe these results, with emphasis on the comparison with other phases of the ISM (HI and ionised gas). Based on a comparison with detailed numerical simulations, for one of the objects we obtain a complete picture of the outflow and find that outflowing molecular gas is present across the entire region co-spatial with the radio plasma, providing unambiguous evidence that the radio jets are driving the outflow. The signature of the impact of the radio jet is clearly seen in the spatial distribution of the excitation temperature and pressure of the outflowing gas, with the highest excitation and pressures found for the gas with the highest outflow velocities. The detailed information about the physical condition of the gas in this fast outflow can serve as template for the signatures of the impact of radio plasma jest on a gas-rich ISM and guide the studies of outflows in other galaxies, including higher redshift objects.

Using BPT-σ relation for study of gas ionization state in local galaxies.

Dmitrii Oparin (Special Astrophysical Observatory of Russian Academy of Sciences)

Study of the warm ISM in star forming galaxies is clues for understanding a galactic evolution and effects of stellar feedback. Emission lines ratio diagrams (also known as Baldwin-Phillips-Terlevich plots) are traditionally used for analysis of the state of an ionized gas emitting in the optical range. This method helps easily to determine the source of ionization in case of high-energy processes, but there are difficulties appearing in intermediate cases. Combining classical BPT-diagrams with another parameter — line-of-sight velocity dispersion of the ionized gas (σ) — helps to solve this problem for objects with shocks ionization. We use velocity dispersion maps obtained with scanning Fabry-Perot Interferometer (FPI) at the 6-m telescope BTA with emission line ratios abtained from the different 3D-spectroscopy data to study several local galaxies with different sources of ionization (violent star formation, galactic wind etc.)

Cosmic ray acceleration at supernova remnants

Matteo Pais (AIP (Leibniz Institut für Astrophysik Potsdam))

Recent work in cosmological simulations suggests that cosmic rays (CRs) are important agents of feedback in galaxies, providing a pressure comparable to that of galactic turbulence and can potentially be responsible for driving galactic winds. Using the moving-mesh code AREPO, here we study their fresh injection into the interstellar medium at supernova remnants (SNRs). The simulations provide a detailed CR morphology of a single SNR for different magnetic field morphologies. Using an obliquity-dependent shock acceleration efficiency for quasi-parallel shocks, this setup is able to predict not only an average acceleration efficiency of about 5 per cent (for a maximum efficiencyof 15% as suggested by kinetic plasma simulations), but also reproduces the observed TeV gamma-ray morphology of SNRs solely by varying the magnetic morphology. This provides a powerful probe to constrain the magnetic coherence scale of SNRs and, consequently, of the local galactic magnetic field. This allows us to constrain the magnetic coherence scale around SN1006 and Vela Jr. to > 200 pc and about 8 pc, respectively.

Spectra and feedback from young stellar clusters

Varsha Ramachandran (Potsdam University)

Clusters of early-type stars are often surrounded by a ’superbubble’ or ’shell’ of hot gas. The formation of such superbubbles and shells is thus directly linked to the stellar feedback from massive stars. Consequently, quantitative analyses of massive stars are required to understand how the feedback of these objects shapes/ creates these large-scale structures of the ISM. We present quantitative spectroscopic analyses, energy feedback, and chemical yields of young stellar populations associated with the superbubble N 206 in the LMC and the supergiant shell SMC-SGS1 in the Wing of the SMC. Both of these regions contain young clusters, NGC 2018 and NGC 602, respectively. We obtained VLT FLAMES spectra of the massive star populations associated with each of these complexes. Available UV spectra are also used in this study. The quantitative spectroscopic analyses are performed with the Potsdam Wolf-Rayet (PoWR) model atmosphere code. The physical and wind parameters obtained from the PoWR modelling are used to calculate the ionizing and mechanical energy input from the massive stars to the ISM. The talk is focusing on the study of massive stellar populations associated with two regions at different metallicity. We discuss the Hertzprung-Russell diagram of massive stars, the star formation history, the present-day mass function, and the age spread in these complexes. The main aim of the study is to quantify the stellar feedback from OB and WR stars. Further, we compare the accumulated mechanical energy input from the OB-type stars, WR stars, and the SN to the stored energy in the superbubble or shell. The talk also gives an idea about the importance of the feedback from OB stars at different environments.

The formation of the largest stellar cores in massive early-type galaxies

Antti Rantala (University of Helsinki)

We study the formation of the largest stellar cores in massive early-type galaxies using our new regularized tree code KETJU. Running high-resolution galaxy merger simulations with supermassive black holes (SMBHs), we are able to simulate the core scouring process by SMBH binaries in detail from the binary formation until the SMBH merger driven by gravitational wave emission. The decline and the characteristic timescales of the central stellar density and the stellar velocity anisotropy are studied in detail. In addition, the scaling relations between the core size, black hole mass and its sphere of influence provide interesting insights into the core formation process.

Controlled merger history in cosmological galaxy formation simulations

Martin Rey (University College London)

I present a new method to study the diversity of the galaxy population. The growth of stellar mass in galaxies is regulated by the competition between inflows and feedback. Fresh cool gas, accreted from the galaxy’s surroundings, is needed to sustain star formation. But this gas is then heated by astrophysical processes inside the galaxy, inhibiting further star formation. Understanding the conditions under which this equilibrium is broken, leading to galaxy quenching, is a major challenge for galaxy formation models. Mergers as violent disruptive events can offer the seed to tilt the balance from one side to the other. They are by definition stochastic, generated by random inflationary perturbations in the early-Universe. I present a method to study the coupling of mergers with the galaxy’s internal response, in the context of cosmological numerical simulations. The method based on genetic modifications (Roth et al 2016) allows us to generate alternative histories of the same galaxy, each history with a carefully designed change. It was successfully applied in Pontzen et al 2017 to study the efficiency of quenching by a central black hole as a function of merger ratio. I present an extension of this technique allowing us to directly control the balance between smooth accretion and mergers in building a given galaxy (Rey and Pontzen 2018). I will show the results from dark matter-only simulations and discuss forthcoming applications to galaxy quenching with hydrodynamical simulations.

The nature and prevalence of cold gas outflows across the local SFR-M* plane

Guido Roberts-Borsani (University College London)

A thorough understanding of the evolution of the cold gas content and quenching mechanisms in star-forming galaxies is a prerequisite towards answering how such objects transit from blue and star-forming to “red and dead”. In this work we perform a stacking of the neutral NaDλλ5889,5895 ISM doublet using the SDSS DR7 spectroscopic data set to probe the prevalence and characteristics of cold (T~10^3 K) galactic-scale flows in local (0.025 ≤ z ≤ 0.1) galaxies across the SFR-M* plane, with the aim of determining whether such outflows can quench normal galaxies. We find low-velocity outflows to be prevalent in regions of high SFRs and stellar masses (10 ≤ log M* ≤ 11.5 M⦿), however do not find any detections in the low mass (log M* ≤ 10 M⦿) regime. We also find tentative detections of inflowing gas in high mass galaxies across the star forming populations. We derive mass outflow rates with ranges 0.1-2.45 M⦿yr-1 and find a strong power law relation between the mass loading factor (η=dm/SFR) and SFR. The slope of this relation suggests local, normal galaxies (inactive and AGN) are not quenched via these outflows. Finally, as outflow detection rates and central velocities do not vary strongly with the presence of an active supermassive black hole, we determine that star-formation appears to be the primary driver of galactic winds at z~0, not AGN.

Feedback in the central parsecs of low-luminosity active galactic nucleus

Alberto Rodríguez-Ardila (IAC-Spain / LNA-Brazil)

Jet-driven outflows are now recognized as an important ingredient in the active galactic nuclei (AGN) feedback scenario. The effects of such mechanism in low-luminosity AGN (LLAGN, log L_bol < 43 erg/cm^2/s) is not yet clear mainly because of the lack of high-angular resolution data. Here, we present challenging results on the feedback mechanisms in a sample of LLAGN by means of near-infrared integral field spectroscopy obtained with SINFONI/VLT. The exquisite angular resolution of a few tens of parsec/spaxel allows us to unveil at unprecedented detail the extension and morphology of the high-ionization gas mapped through the [SiVI] 1.963 micron line. The high-ionization gas (HIG) displays an intricate and complex morphology, following the radio-emission and extending to distances of up to hundreds of parsecs. Bubbles and shells of [SiVI] emission, likely inflated by the thermal expansion produced by the passage of the radio-jet are observed in some objects. We measured outflow mass rates of a few solar masses per year, similar to those found in powerful radio-galaxies and classical Seyferts. Our results highlight the importance of the mechanical feedback in LLAGN and show that its effects to the ISM cannot be underestimated.

The AGN fueling/feedback cycle: a multi-phase study of a sample of local radio galaxies

Ilaria Ruffa (INAF-IRA/University of Bologna)

Galaxy formation theories struggle to explain the role of Black Hole accretion in shaping galaxies over cosmic time. Radio feedback, associated to radio jets, is accepted as a fundamental component of the lifecycle of the most massive radio loud early-type galaxies (ETGs), at least in the late stages of cosmic evolution (z < 1). The many details of such process, however, still remain poorly understood. It is generally accepted that High Excitation Radio Galaxies (HERGs) are triggered by cold gas transported to the center through merging or collisions with gas-rich galaxies, while accretion in Low Excitation Radio Galaxies (LERGs) may occur directly from the hot gas phase. The most compelling evidence that cold gas can play a role in fueling LERGs as well, is that in such systems dust and cold gas are detected in larger quantities than in radio-quiet ETGs. The origin of this gas (external or secular) still remains unclear. Our overall project aims at exploring the multi-frequency properties of a volume-limited sample of eleven nearby (z < 0.03) LERGs, selected from the Ekers et al. (1989) parent sample of 90 radio galaxies from the Southern Parkes 2.7 GHz survey. Our purpose is to conduct an extensive study of different galaxy components (stars, warm and cold gas, radio structure), which will enable us to draw an exhaustive picture of the AGN fuelling/feedback cycle in LERGs. For all the sources, we have already acquired a set of multi-wavelength data, spanning from the radio to the optical regime. Here we present the results obtained by analyzing ALMA Cycle 3 CO(2-1) observations of 9 targets, with resolutions of few hundreds of parsecs (at the source redshifts). The CO(2-1) line emission was detected in 6 out of 9 targets (66% detection rate) at high significances (8-45sigma). CO(2-1) maps show rotating disc structures in all the sources, with some peculiar cases in which the gas disc shows a disturbed morphology that seems to suggest an interaction with the radio jets. The CO discs are mostly located in the inner kpc-sub-kpc scales of the host galaxy. Using the available optical images, we investigated the relative dust and gas distribution: they result mostly co-spatial, with dust extending on larger scales in some cases. The study of the CO kinematics is still ongoing, but preliminary results show hints of the presence of of non-circular motions (i.e. inflow/outflow) in at least one of the detected CO discs.

Reproducing the observed diversity of dwarf galaxy rotation curve shapes in LCDM

Isabel Santos-Santos (Univ. Autónoma de Madrid)

The significant diversity of rotation curve (RC) shapes in dwarf galaxies has recently emerged as a challenge to cold dark matter (LCDM): in dark matter (DM) only simulations, DM haloes have a universal cuspy density profile that results in self-similar RC shapes. We compare RC shapes of simulated galaxies from the NIHAO project with observed galaxies from the SPARC data set and LITTLE THINGS survey. NIHAO includes a feedback implementation that naturally produces galaxies hosted in haloes that have undergone a wide spectrum of halo responses, from contraction to expansion. The degree of expansion has been shown to depend primarily on the stellar-to-halo mass ratio and then eventually, at a given stellar mass, also on size, with larger galaxies being more susceptible to expansion. By means of the V2kpc–VRlast relation (where VRlast is the outermost measured rotation velocity), we show that both the average trend and the scatter in RC shapes of NIHAO galaxies are in reasonable agreement with observational data. NIHAO galaxies can reproduce even the extremely slowly rising RCs of IC 2574 and UGC 5750. Revealingly, the range where observed galaxies show the highest diversity corresponds to the range where core formation is most efficient in NIHAO simulations. A few observed galaxies in this range cannot be matched by any NIHAO RC nor by simulations that predict a universal halo profile. The majority of these are starbursts or emission-line galaxies, with steep RCs and small effective radii, suggesting that central starburst activity is closely linked to a high central dynamical mass in dwarf galaxies. These results represent a significant improvement compared to simulations that do not result in DM core formation, suggesting that halo expansion from feedback is a key process in matching the diversity of dwarf galaxy RCs.

Inverse Compton scattering on quasar 1045-18 emission as possible mechanism of X-rays generation in kiloparsec-scale jet

Elena Shablovinskaya (Special Astrophysical observatory of Russian Academy of Science)

M.S. Butuzova1, E.S. Shablovinskaya2 1) Crimean Astrophysical Observatory of RAS 2) Special Astrophysical Observatory of RAS Inverse Compton scattering on cosmic microwave background [1] as the mechanism of X-ray emission origin in kpc-jets of core dominated quasars had been the most commonly used model for more than 15 years. Yet, presently it was denied for several sources (see, e.g., [2]) due to the absence of predicted high level of X-ray flux. We suggest an alternative scenario of X-rays origin in kpc-jet of quasar 1045-18 – the model of Inverse Compton scattering on central source emission (active nucleus, parsec-jet and its surroundings). In case of such a suggestion we obtained a low limit to the inclination angle of jet to the line of sight and estimation of jet knots physical parameters. This work was supported of the Russian Foundation for Basic Research (project 18-32-00824). 1. Tavecchio F., Maraschi L., Sambruna R.M., Urry C.M. ApJ, 544, L23, 2000. 2. Meyer, Georganopoulos, Sparks et al. ApJ, 805, 154, 2015.

Intraday variability of blazar s5 0716+714 in polarized light

Elena Shablovinskaya (Special Astrophysical observatory of Russian Academy of Science)

The bright radiosource s5 0716+714, that is usually classified as BL Lac type, is one of the most intensively studied objects. s5 0716+714 demonstrates extremely peculiar properties such as flux variability flux both on long and short timescales. In given talk the results of 9-hour polarimetric monitoring of s5 0716+714 with the 70-second resolution, carried out at 6-m telescope BTA of SAO RAS, would be presented. The observation data analysis reveals the existence of variability both in total and polarized light on the 1-1.5-hour timescales. The numerical model of polarization in jet with helical structure of magnetic field is suggested and is in agree with our observations and other authors’ results.

Large-scale ionized gas filaments in Mrk 6: nuclear outflow or external gas accretion?

Aleksandrina Smirnova (SAO RAS Russia)

Using various techniques of optical observations at the Russian 6-m telescope (broad-band and narrow-band images, long-slit and 3D spectroscopy), we have investigated the large-scale morphology and kinematics of ionized gas in the well-known Seyfert galaxy Mrk 6. Having a significantly deeper limit than that in previous studies, we both mapped the ionized gas in the whole stellar disc and also found a system of faint filaments elongated in the NE direction up to a projected distance of 39 kpc. By studying the kinematics as well as the ionization state of the gas in this galaxy and deep images of the Mrk 6 environment taken with Byurakan 1-m Schmidt telescope, we try to find out the nature of these filaments.

Horizon Run 5 - tuning a large volume simulation

Owain Snaith (KIAS)

I will present the Horizon Run 5 simulation, which is a new cosmological hydrodynamical simulation that will capture physics on scales ranging from Gpc to kpc. This simulation will be carried out using a version of the RAMSES adaptive mesh refinement code, and will achieve a resolution of 1 kpc while simultaneously capturing BAO scales. We incorporate AGN feedback from Dubois et al. (2012) and stellar feedback and chemical yields from Few et al. (2012). I will present preparatory work tuning the baryonic physics, especially the AGN and stellar feedback parameters of the simulation. I will discuss the sensitivity of the results of our test runs on the feedback parameters, and focus on the cosmic star formation rate, specific star formation rate, galaxy stellar mass function and galaxy colours. I will discuss the consequences of the sensitivity of these galaxy properties to the applied feedback prescriptions for future simulations.

Exploring the parsec-scale structure of multi-phase outflows

Martin Sparre (AIP)

We explore the evolution of cold spherical gas clouds accelerated by a hot wind as a simplified setup for studying the physical state of thermally unstable galactic outflows. Recent 2D simulations by McCourt et al. (2017) have suggested that radiative cooling "shatters” massive dense structures into small cloudlets with a size comparable to the cooling scale of order 0.1 pc for typical galactic parameters. Using simulations with the moving-mesh code Arepo, we confirm these results in 2D and quantify the fragmentation process with a cloudlet-finding algorithm and power spectra. We also present the first 3D simulations that have high enough resolution to resolve shattering. We finally present a set of ongoing simulations, which explores the effect of magnetic fields, anisotropic thermal conduction and self-gravity.

Structure and amplification of magnetic fields in Milky-Way-like galaxies

Ulrich Steinwandel (University Observatory Munich / Max Planck Institute for Astrophysics)

We present a set of high resolution simulations of isolated Milky Way-like galaxies with a mass resolution of 4e3 solar masses. We include a spherical circum galactic medium (CGM) that is constrained by observations and cosmological simulations and investigate the impact of magnetic fields in these galaxies. The simulations are carried out with the Tree-SPH-Code Gadget-3. We perform three different sets of simulations with different approaches to handle initial magnetic fields. In the first model we use a homogeneous constant magnetic seed field of 1 nG strength in x-direction. In the second model we instead seed magnetic dipoles in a local region around each statistical supernova event by a direct coupling to the subgrid star formation and feedback model. The third set consists of control runs without magnetic fields. Magnetic fields affect the galactic properties in several ways. We observe a drop of the star formation rate with both magnetic field models compared to the control runs. This is due to a wind driven by a break up of the magnetic field lines perpendicular to the galactic disc plane once the magnetic pressure dominates over the thermal pressure. We observe that this magnetic wind reduces the discs mass by around 10 percent. The mean magnetic field strength in the galactic disc saturates at a few µG which is in good agreement with observations [1]. In the galactic centre we reach maximum magnetic field strengths of around 500 µG which is also in agreement with observations where values in the mG regime can be found [4]. Analyzing the field structure reveals that the maximum values are reached between the galactic spiral arms. This is supported by observations [1] and can be explained by diffusive terms that are included in the induction equation. Most importantly, we find strong evidence that the magnetic field is amplified by a small scale turbulent dynamo consistent with the Kazantsev-dynamo theory [2] indicated by powerspectra of the Alfvén velocity in both magnetic field models as well as by the anti-correlation of the magnetic field strength and the curvature of the magnetic field lines [3]. Summing up, our findings indicate that magnetic fields can be an important feedback mechanism once they becomes dynamically relevant and will be published in an upcoming paper. [1] Beck, R 2007 2007,A&A,470,539 [2] Kazantsev, A 1968,Soviet Physics JETP,26,1031 [3] Schekochihin, A et al. 2004,ApJ,612,276 [4] Yusef-Zadeh, F et al. 1996,ApJ,466,L25

Evolution of galactic outflows studied with metal absorption lines in optical spectra

Yuma Sugahara (Univ. of Tokyo)

Relationship between galactic-outflow and host-galaxy properties is a key to understanding feedback processes driven by outflows and being studied in multi-wavelength ranges at various redshift. In previous studies, however, galaxy spectra are not analyzed in the same manner, which makes it difficult to discuss the evolution of outflows. We present observational results of the evolution of galactic outflows in star-forming galaxies based on metal absorption lines in optical spectra. The spectra of galaxies at z ~ 0, 1, and 2 are taken from the large-survey data sets of SDSS DR7, DEEP2 DR4, and Erb et al., respectively. We carefully construct large and homogeneous samples with similar stellar mass distributions ranging from 10^9 to 10^11.5 solar mass. We construct composite spectra and perform the multi-component fitting of model absorption lines to calculate outflow velocities. We identify, for the first time, that the average outflow velocity monotonically increases by 0.1--0.4 dex from z ~ 0 to 2 at a given star formation rate. Provided that the outflow velocity has a tight correlation with SFR surface density (Sigma_SFR), the evolution of the maximum outflow velocities is consistent with the size evolution of star-forming galaxies. As next steps, we apply the stacking method to spectroscopic samples at z ~ 0 and z > 2. At z ~ 0, larger SDSS sample that consists of ~ 100,000 star-forming galaxies enables us to compute statistical properties of galactic outflows. Using high-S/N composite spectra in bins of five galaxy properties, we find that the threshold for driving outflows is Sigma_SFR >~ 10^(-1.75) [Msun yr^-1 kpc^-2], which is five times lower than the classical threshold of Sigma_SFR >~ 10^(-1.0). Moreover, the outflow velocities have a good correlation with all of the SFR, stellar mass, and u-band size. With spectra of galaxies at z > 2, we derive the outflow velocities in a uniform manner adopted at z ~ 0--2. Comparing the observational results at z > 2 with the evolution at z ~ 0--2 and the statistical properties at z~0, we will discuss the evolution of outflow velocities from z ~ 0 to 6.

Testing the robustness of massive black hole mass measurements using ALMA and MUSE

Sabine Thater (AIP)

Over hundred massive black hole (MBH) mass measurements of local galaxies have revealed strong correlations with different properties of their host galaxy bulge. However, determining MBH masses is a challenging procedure and possible biases need to be recovered before properly understanding the underlying physics.I present two projects to address the following questions: Do high-mass and low-mass black holes follow the same scaling relations? Does the variety of mass measurement methods force an additional bias on the scaling relations? Therefore, I present our SMASHING sample of 20 early-type galaxies which expand the scaling relations on both the high and low mass end. Then, I show the comparison of two independent MBH determinations from stellar kinematics (MUSE) and the novel molecular gas kinematics technique (ALMA), taking special care in revisiting the associated measurement errors, specifically, the systematics associated with the dynamical methods, and the general accuracy of MBH mass measurements.

Alfvén-Wave regulated Cosmic Ray Hydrodynamics

Timon Thomas (Leibniz-Institut für Astrophysik Potsdam)

Cosmic Rays (CRs) are relativistic charged particles which are promising candidates to provide feedback on star formation. They contribute to the pressure balance of a galaxy and are even capable to drive winds away from galactic disks. Due to their small number density CRs form a collisionless particle population that interacts with the ambient gas predominately by electromagnetic fields. On the kinetic scale CRs get scattered by and excite turbulent Alfvén waves. Damping of these waves channels energy and momentum from CRs to the thermal gas. In this work we present a new theory which models CRs in a hydrodynamic framework and derive a new set of equations that self-regulates CR transport on a macroscopic scale. Our theory correctly restores the equations of classical CR hydrodynamics in a steady state limit. We analyse our theory using numerical simulations and compare it to currently used numerical algorithms which simulate classical CR hydrodynamics.

Radio-jet and galaxy interplay in nearby isolated ellipticals, brightest group ellipticals, and rare transitional galaxies

Sravani Vaddi (National Centre for Radio Astrophysics)

AGN feedback is now well recognized and is included in numerical and semi-analytic models as an important process in the galaxy - black hole co-evolution. Our multi-wavelength study on a sample of nearby isolated ellipticals and nearby galaxy groups suggests that feedback may not necessarily impact the growth of the host galaxy. It depends on the galaxy mass and thus on the black hole mass; there is a threshold in the black hole mass above which feedback can have a significant effect on the host galaxy. These results suggest an indirect sign to feedback and an observational smoking-gun evidence of AGN affecting the host galaxy is missing. Synchrotron-age dating of radio relic emission can be used to trace back AGN activity and correlate with the star formation history. With the help of the upgraded Giant Metrewave Radio Telescope (uGMRT), we are studying the past AGN activity of a sample of sources together with their star formation. We present three intriguing cases of jet-galaxy interaction as ideal laboratories in investigating the details of the physical processes in feedback - (a) two cases of radio jet interacting with the ISM of a companion galaxy, (b) two merging galaxies showing episodic activity likely triggered by the merging activity but with no signs of enhanced star formation.

Self-sustaining star formation fronts in filaments during cosmic dawn

Xiawei Wang (Harvard University)

We propose a new model for the ignition of star formation in low-mass halos by a self-sustaining shock front in cosmic filaments at high redshifts. The gaseous fuel for star formation resides in low mass halos which can not cool on their own due to their primordial composition and low virial temperatures. We show that star formation can be triggered in these filaments by a passing shock wave. The shells swept-up by the shock cool and fragment into cold clumps that form massive stars via thermal instability on a timescale shorter than the front's dynamical timescale. The shock, in turn, is self-sustained by energy injection from supernova explosions. The star formation front is analogous to a detonation wave, which drives exothermic reactions powering the shock. We find that sustained star formation would typically propel the front to a speed of ~ 300-700 km/s during the epoch of reionization. Future observations by the James Webb Space Telescope could reveal the illuminated regions of cosmic filaments, and constrain the initial mass function of stars in them.

Simulating galaxy formation with cosmic rays: the multi-frequency view

Maria Werhahn (AIP)

We aim at understanding the underlying physics of the far-infrared (FIR)—radio correlation of star-forming galaxies by performing high-resolution magneto-hydrodynamic simulations of galaxies using the moving mesh code AREPO with self-consistent cosmic-ray (CR) physics. These CRs are accelerated at supernovae and are thus connected to young stellar populations, which emit predominantly ultra-violet (UV) radiation that is absorbed by dust and re-emitted in the FIR. On the other hand, multiple radiation processes occur due to the acceleration of CRs. First, primary electrons gyrate around magnetic field lines and emit radio synchrotron radiation. Furthermore, they can Compton up-scatter photons from the ambient radiation field (comic microwave background, stellar and dust radiation) and emit bremsstrahlung in the gamma-ray regime. Second, CR protons interact hadronically with the ambient medium, which leads to the production of pions. While the neutral pions decay into gamma-rays, charged pions are a source of secondary electrons that again contribute to the leptonic radiation processes. We show a multi-frequency spectrum due to all non-thermal emission processes of our simulated galaxies (dwarfs to Milk-Way sized) and compare primary and secondary contributions. This enables us to calibrate the strength of cosmic ray feedback as a function of galaxy mass and star formation rate ranging from quiescent galaxies to starbursting phases.

Cosmic Ray Bottlenecks in Galactic Halo Cool Clouds

Joshua Wiener (UW Madison)

Cosmic rays (CRs) are energetically important in a range of astrophysical environments. As such they can have significant dynamical and thermal effects on the ambient medium. One notable example where high CR pressure gradients may be important is in cool (10^4 K) clouds in the hot (10^6 K) ionized medium of galaxies. In the streaming model of CR transport, CRs flowing through such clouds will see a local minimum in streaming speed. This minimum acts as a bottleneck for CR transport, causing the buildup of significant CR pressure gradients. I will present the results of a series of ongoing numerical simulations that explore the consequences of this bottleneck effect. I will focus on the potential acceleration of the clouds, resulting in high velocities, and on wave heating of cloud interfaces, resulting in larger high ion column densities.

Cosmic Ray Electrons in Galaxy Formation

Georg Winner (Leibniz Institut für Astrophysik Potsdam (AIP))

Cosmic rays play an important role in galaxies. Despite their low number densities compared to the intersteller medium, the energy contained in cosmic ray protons (CRp) is in equipartition with turbulent and magnetic energy. The energy of cosmic ray electrons (CRe) falls short by a factor of 100, but very fast cooling processes make CRe radiate far more efficient than CRp and make them an important to link to observables in the radio and gamma ray regime. Therefore it is inevitable to carry out simulations of galaxies and galaxy clusters with CRe and evolve their spectrum with time in order to derive their radiation profile. We present a new code for evolving the spectrum of CRe dynamically in space and time together with the moving-mesh code AREPO. The CRe spectrum is evolved following the Fokker-Planck equation and Coulomb and radiative loss processes, adiabatic gains and losses, secondary CRe injection, diffusive shock acceleration as well as turbulent reacceration are taken into account. Supernova remnants are the most reliable candidate for particle acceleration in our galaxy and are strong gamma ray emitters. We use our framework to simulate supernova remnants as spherically expanding blast waves, derive the radiation from CRe and discuss leptonic vs hadronic emission models. We further give an outlook to galactic outflows and especially the Fermi bubbles where the leading model for the gamma ray emission is the inverse Compton scattering of CRe.

The long-term evolution of AGN-outflow correlations

Kastytis Zubovas (Center for Physical Sciences and Technology, Vilnius)

The observed AGN-driven outflows have properties, such as mass outflow rate, momentum rate and kinetic energy, that correlate very well with AGN luminosities. Furthermore, these correlations agree remarkably well with predictions of simple analytical model. This is actually rather strange, because AGN episode durations are an order of magnitude shorter than outflow expansion timescales, therefore the observed AGN episode is almost certainly not the one that inflated the observed outflow. I will present several results of investigating the long-term evolution of AGN wind-driven outflows and show how their properties can help us disentangle the accretion history of the central black hole. In particular, the lack of observed outflows with momentum and energy rates far higher than analytically predicted implies that AGN fade slowly, with power-law, rather than exponential, time dependence of luminosity. The existence of massive outflows at significantly different spatial scales allows us to identify multiple past and/or present accretion episodes. Finally, the stellar mass at which the transition between small galaxies dominated by stellar feedback and massive galaxies dominated by AGN feedback occurs suggests that AGN feedback must be very efficient, i.e. that >5% of the AGN luminous energy output must be used to drive the outflow. These findings build up a picture of understanding outflows as a long-term footprint of galactic activity.