18th Potsdam Thinkshop

13 Jul 2025, 16:30 → 18 Jul 2025, 18:00 Europe/Berlin

Conference Room, Maria-Margaretha-Kirch building (Leibniz Institute for Astrophysics Potsdam (AIP))

When: July 14 - 18, 2025 (starts with a reception on July 13, 17:00)

Where: Potsdam, Germany

Contact: cpfrommer@aip.de

News & Updates:

- Poster size: All our poster boards are (at least) 1 m wide and 1.4 m high. Please do not exceed these dimensions as it might be difficult to display oversized posters.

- Cancellation policy: In response to a recent question, please note that refunds for the conference fee in case of cancellation can only be issued until June 25, as we must confirm the number of attendees with the caterer by that date.

Abstract

We intend to host the 18th Potsdam Thinkshop in 2025, with a focus on understanding the role of feedback in galaxy formation. We plan to cover all subjects directly related to feedback including stellar and active galactic nuclei feedback, interstellar medium, circumgalactic medium, mechanical feedback, magnetic fields and cosmic rays, radiative feedback, etc. from both an observational and theoretical point of view. 

Social media

Please join us on Bluesky at #thinkshop2025

Scientific Rationale

Centaurus A. Image Credit: ESO and Chandra composite image.

Galaxies come in various shapes and sizes ranging from spirals to ellipticals - which processes are mainly responsible for their formation and appearance? How do transformative processes affect the characteristics of galaxies? Observations indicate that the mass of a galaxy is a discriminating factor in its ability to effectively turn gas into stars. But why are galaxies like our own Milky Way apparently the most efficient in producing stars, while dwarf galaxies and galaxy clusters struggle? Is "feedback" the answer? and if so, what is the underlying physics? Or do we need to go beyond Occam's razor and add additional interactions to otherwise cold dark matter? What do we know for sure, which ideas play most likely an important role and what is pure speculation about our modern understanding of galaxy formation?

The number of observational studies of galaxies is rapidly increasing as a consequence of new techniques such as integral field spectroscopy, and major improvements at radio, optical, infrared, ultraviolet, X-ray, and gamma-ray frequencies. In particular, recent JWST and MUSE observations have sharpened our understanding of the ISM in nearby galaxies, the emergence of galactic winds and opened up new puzzles about the early growth history of galaxies at high redshifts. These observations over the entire electro-magnetic spectrum have allowed astronomers to spatially resolve internal properties of galaxies with unprecedented detail, and are thus providing key insights towards understanding the structural components of galaxies, their star-formation processes, kinematics, stellar populations, metal distribution, and nuclear activity, as well as how galaxies evolve with time. They provide important clues of how cold gas accretes from the circumgalactic medium (CGM), collects in the disk, is converted into stars and returned to the CGM in this cosmic cycle of baryons. 

M82. Image Credit: Hubble and Chandra Composite image

These endeavours are complemented by the latest generation of galaxy simulations, which push forward higher resolution and model the multi-scale physics of the interstellar and circumgalactic media in ever-increasing detail. These simulations can derive insights from idealized problem setups of small-scale physics, including but not limited to the multi-phase structure of galaxies and plasma physics processes. Those models are accompanied by simulations that trace galaxy evolution following the hierarchical Lambda cold dark matter scenario with many physical processes included, opening the possibility of performing realistic mock observations and comparisons to observational data. 

The aim of the 18th AIP Thinkshop is to bring together leading international experts and young researchers working in both Galactic and extragalactic astronomy. We aim to discuss the different physical feedback processes shaping galaxies, including stellar and AGN feedback, mechanical feedback, magnetic fields and cosmic rays, radiative feedback, etc. from both an observational and theoretical point of view. We will also discuss the interplay of the different components of a galaxy (stars, interstellar and circumgalactic media, non-thermal components including cosmic rays, magnetic fields, and turbulence, dust, and dark matter), and whether we can find smoking-gun observables identifying the dominating feedback agents during some specific epoch and halo mass range. The final objective is to reach a better understanding on the feedback processes that rule the evolution of galaxies. 

Topics

• The role of feedback in self-regulating star formation and ISM properties in galaxies
• Physical properties of gaseous halos and imprints of feedback on them
• Circulation of metals and gas in and out of galaxies
• Observational evidence for feedback
• Theoretical challenges in modelling feedback
• Galaxies: stellar feedback
• Active galactic nuclei feedback
• Feedback via supernovae, cosmic rays and radiation
• Impact of cosmological environment on feedback processes

 

Previous Thinkshop on “The role of feedback in galaxy formation”

After the great success of our inaugural Thinkshop on “The role of feedback in galaxy formation” in 2018, we would now like to discuss the progress in this exciting and vibrant field since then. Please have a look at the website of the previous Thinkshop 15 to get an idea of what to expect from the planned event in 2025.

 

 

Header image: The Galactic Center in Radio from MeerKAT
Image Credit: Ian Heywood (Oxford U.), SARAO; Color Processing: Juan Carlos Munoz-Mateos (ESO)

Sunday, 13 July

Registration

Reception

Monday, 14 July

Registration

Reception: Welcome address

Talks: SN & ISM 1

Convener: Kathryn Kreckel (Heidelberg University)

1 Invited Talk

Speaker: Thorsten Naab

2 The interaction between stars and the ISM on “cloud scales” unveiled by machine learning

HII regions are fundamental units of the matter cycle in galaxies and their optical emission serves as the main lens through which we study star formation and chemical enrichment across the Universe. They are the sites where ionising radiation and stellar winds have their main impact, turbulence is injected, and heavy elements are dispersed into the interstellar medium. The sizes and internal structure of HII regions are therefore critical observables to quantify the relative role of different possible pre-supernova feedback mechanisms and provide constraints on the overall stellar feedback energetics to simulations.

In this talk I will present recent results showcasing the spatially resolved structure of HII regions, leveraging the multi-wavelength archive of data of nearby galaxies from the PHANGS survey and observations of Local Group galaxies like M33. I will demonstrate how we are using machine learning to analyse large integral field spectroscopy datasets to detect and classify nebulae. I will then discuss the links between nebulae and their stellar feedback sources. In particular, I will show how the combination of photoionisation modelling and the study of the properties of the ionising stellar sources will enable direct measurements of the escape fraction of ionising photons on cloud scales.

Speaker: Francesco Belfiore (INAF - Arcetri Astrophysical Observatory)

3 The (Un)Changing ISM and the Impact of Feedback in FIRE Galaxies through Cosmic Time

In this talk I will present results from the FIRE cosmological zoom-in simulations exploring the (un)changing properties of the ISM through cosmic time, from redshift three to zero. I will highlight how on (sub)kiloparsec scales, several important properties of the ISM do not change as the galaxies grow and evolve from dispersion-supported, star-bursting objects to rotation-supported, smoothly star-forming disks. In particular, the importance of equilibria and stability against gravitational fragmentation and collapse on the gas scale height will be discussed. Intriguingly, gas appears to arrange itself with feedback in a manner so as to maintain marginal stability, regardless of the large-scale galaxy morphology, provided the entire gas reservoir is not being affected by a major merger. For this reason, I will show how though many variables are changing across the history of these galaxies, e.g., star formation rates, gas fractions, how feedback is coupling to the ISM, turbulent gas velocity dispersions, cold gas fractions, the underlying (dynamic) equilibrium of the ISM is not. Lastly, I will point to observational consequences of this underlying dynamical equilibrium that will be testable by the current and next generation of IFU surveys of extragalactic gas, star formation, and feedback on the sub-kiloparsec scale.

Speaker: Matt Orr (Flatiron Institute & Rutgers University)

4 Structure and porosity of the multiphase ISM in nearby spatially resolved galaxies

Nearby galaxies observed at high spatial resolution with JWST, ALMA, and MUSE allow us to address fundamental questions related to the influence of young stars on their surrounding interstellar medium (ISM), from cloud to galactic scales: How far can ionizing photons travel, and what physical mechanisms favor their escape from HII regions? How do such processes shape the ISM and influence galactic evolution?

I will first present constraints on the timescales and physical mechanisms associated with the evolutionary cycle of molecular clouds in 30 galaxies from the PHANGS-JWST survey, including their dust-embedded star formation phase. We find that the embedded phase of star-formation is typically short (< 4 Myr) and is drastically reduced in late-type galaxies. Strikingly, this phase seems absent in galaxies with a relatively metal-poor ISM, that may host different populations of HII regions, possibly associated with ionizing photon leakage.

To further investigate the physics at play in such environments, I will present results obtained on a sample of 13 resolved dwarf galaxies observed with MUSE, extending the metallicity range probed by PHANGS. Using multicomponent models to interpret their spectral data, we infer the main physical properties of their HII regions, including the escape fraction of ionizing photons, and assess how the local porosity to UV photons may affect the ISM at larger scales.

Speaker: Lise Ramambason (Heidelberg University)

5 Panel of 4

10:40 COFFEE & POSTER

Talks: CRs & Radation

Convener: Maria Werhahn

6 Invited Talk

Speaker: Mattheusz Ruszkowski

7 Unraveling the interplay of cosmic ray and stellar feedback in galaxy formation

The interstellar and circumgalactic media are the two important reservoirs that fuel star formation in galaxies. Their highly turbulent internal dynamics are shaped by feedback processes such as supernova (SN) explosions and subsequently accelerated cosmic rays (CRs). With recent advances in the hydrodynamical modeling of the interactions between CRs, magnetic fields, and their environment, it became possible to quantify the impact and model the transport of CRs in the multiphase interstellar and circumgalactic media with unprecedented accuracy and detail. Numerical modeling of the plethora of microphysical processes and astrophysical feedback channels is challenging and motivated us to develop the CRISP (Cosmic Ray and InterStellar Physics) model, which incorporates the relevant CR and ISM physics for galaxy formation in a single-cast numerical framework. We will present the results of a suite of isolated high-resolution CRISPy galaxy simulations designed to understand the role of CR, SN, and radiative feedback in shaping the dynamics in and around galaxies. We will 1) show how the presence of CRs tangibly changes the galactic wind driving process and the thermodynamical structure of galactic winds, 2) highlight the morphological differences between CR-affected and unaffected inner circumgalactic media, and 3) discuss implications of these two effects for metal ion column densities probed by absorption line studies.

Speaker: Timon Thomas (Leibniz-Institute for Astrophysics Potsdam)

8 Probing cosmic-ray driven winds with deep radio observations

Modern computational advancements have brought about a resurgence in the consideration of cosmic-rays for driving galactic outflows. This is particularly important in normal galaxies whose thermal and radiation pressure alone is insufficient to expel gas and dust from the disk. Synchrotron radio emission is one of the only—and by far the most accessible—direct tracers of cosmic-rays in galaxies. While deep radio images trace the diffusion of cosmic rays from star-forming regions in the disk, they also unveil the expulsion of cosmic rays into the surrounding circumgalactic material (CGM). I will present the serendipitous discovery of a potential case for purely cosmic-ray driven superwinds in a nearby galaxy. Combining the radio synchrotron signatures with HI spectral line imaging, optical integral field spectroscopy, and X-ray observations fully account for all phases of the ISM and CGM. Using this comprehensive approach, I will detail the likelihood that these are primarily cosmic-ray driven winds and how we can further constrain the presence of these winds in future multiwavelength datasets.

Speaker: Allison Matthews (Carnegie Observatories)

9 The formation of a meta-stable CR corona round Milky Way analogues

Despite the many successes of cosmological galaxy formation and evolution simulations, they commonly implement baryonic feedback in a phenomenological manner by calibrating “boosting” parameters, which somewhat diminishes their predictive power and restricts their usefulness in interpreting observational data. An alternative approach is to improve the modelling of feedback processes from first principles, by self-consistently including components which have by-and-large been overlooked. One of these alternatives has been to model cosmic rays (CRs) injected by supernova shocks, which has been seen to have a drastic effect on the evolution of Milky Way-like galaxies and the thermal state of their interstellar medium (ISM). Given their slow-cooling properties, they can efficiently transport stellar-injected energy from the ISM to the large scales of the circum-galactic medium (CGM). Using a suite of high-resolution cosmological zoom simulations of a Milky Way analogue including magnetic fields and CR injection via supernovae, we have explored the role of CR feedback in the thermo-dynamical state of the CGM. While simulations without CRs present the classical, cold filamentary accretion at high redshift, strong feedback in the CR simulation disrupts these inflows well beyond the virial region, resulting in lower-density material approaching the inner halo. This deceleration of streaming inflows creates a reservoir of low-velocity gas at a distance between 0.3 and 0.5 times the virial radius. We have determined that this
reservoir of low-velocity gas is predominantly warm ionised gas supported by CR pressure gradients, continuously heated by the UV background. We term this newly characterised region of the CGM the meta-stable CR corona. Based on this new understanding of the dynamical properties of inflows and the CGM in the presence of CRs, we present criteria for the stability of cosmological accretion shocks taking into account CR heating and transport, as well as a CR+thermal gas mixture. We present how these results can be used to extend current models of galaxy formation to take into account the multi-scale impact of CRs across cosmic time.

Speaker: Francisco Rodriguez Montero (KICP, University of Chicago)

10 Panel of 4

13:00 LUNCH

Talks: Winds 1

Convener: Jake Bennett (Center for Astrophysics | Harvard & Smithsonian)

11 Invited Talk

Speaker: Matthew Smith

12 Observing Neutral Outflows in High-Redshift Galaxies with JWST

Thanks to the unprecedented sensitivity of JWST/NIRSpec, we are now able to study neutral atomic outflows in massive galaxies at high redshift. By detecting optical resonant lines such as Na D and Ca K, which have long been inaccessible from the ground, we have characterized the velocity and mass outflow rate of the neutral phase for a representative sample of galaxies at z~2, finding that powerful neutral outflows are widespread. Compared to ionized outflows, neutral outflows are slower but carry substantially more mass. To ensure the robustness of these results, we calibrated indirect tracers such as the Na D and Ca K absorption lines against a direct measurement of the hydrogen column density. We also analyzed the physical driver of neutral outflows, finding that AGN feedback is likely involved, at least for the quiescent systems. These recent JWST observations thus enable a direct comparison of multi-phase outflows in massive galaxies at Cosmic Noon to the predictions of numerical models.

Speaker: Sirio Belli (Università di Bologna)

13 New Constraints on Molecular Gas Outflows in Massive SFGs at z = 0.5 − 2.6

Feedback in the form of outflows is believed to be a key ingredient in galaxy evolution. In cosmic noon galaxies, outflows have mainly been detected - and extensively studied - in the ionised gas phase. However, it has been surmised that a large fraction of outflowing mass may be in molecular gas form, as suggested by results of luminous but rare AGNs and quasars. To gain insights into the prevalence and impact of molecular gas outflows on galaxy evolution as a whole, we searched for the telltale broad velocity signature in CO line emission, capitalizing on the IRAM/PHIBSS CO survey of 175 typical near-main-sequence star-forming galaxies at 0.5<z<2.6 and using spectral stacking techniques to reach SNRs $> 30$ for the full sample and various physically-motivated subsets. The results suggest that - if present - the molecular gas outflow signature is remarkably weak. Complementary to this, we investigate the spatially resolved CO emission of three z $\sim 2$ galaxies showing prominent ionized gas outflow signatures and find no molecular gas counterpart. We will discuss implications on the molecular outflow properties, galaxy evolution, and future observational work on feedback through outflows at cosmic noon.

Speaker: Capucine Barfety (Max Planck Insitute for Extraterrestrial Physics)

14 Complex outflows lead to simple relations: how M-sigma emerges in a multiphase environment

Massive, large-scale galactic outflows are well known to be important to galaxy evolution. They shape the high-mass end of the mass function, enriching the circumgalactic and intergalactic medium, preventing the cooling catastrophe in galaxy clusters and so on. They also presumably establish the observed correlations between supermassive black holes and their host galaxies, such as the M-sigma relation. A simple analytical model posits that this relation arises when the Eddington-limited luminosity of the AGN, powered by accretion on to a black hole of mass M, provides just enough momentum to the surrounding gas to drive it out of the galaxy’s gravitational potential characterised by the velocity dispersion sigma. This model predicts the slope and scaling of the relation that are very close to observed values. However, real outflows are most likely driven by not only the momentum, but also the energy input from the AGN wind. Naively, this should lead to gas removal from the galaxy at much lower luminosities and, consequently, much lower black hole masses than observed.

The solution to this conundrum lies in the inherent non-spherical and multiphase nature of the interstellar medium. AGN energy-driven outflows expand due to the high pressure of the shocked AGN wind bubble. This is much easier to do in directions of lower density. So the energetic outflow expands through low-density channels, leaving high-density clouds in its wake. These clouds can continue to efficiently feed the black hole, unless the momentum of the AGN wind is high enough to push them away. That way, the M-sigma relation is reestablished.

I will present the results of a set of tightly controlled, progressively more detailed numerical simulations designed to capture the details of AGN energy-driven outflow propagation in a turbulent medium and its interaction with dense clouds. I will show that cooling of the outflowing gas leads to energy-driven outflows being weaker than the simple analytical model predicts, bringing their properties more in line with observations. I will also show that the dense clouds are pushed away and ablated by outflows driven by black holes having masses appropriate for the M-sigma relation. Finally, I will show how the observed relationships between AGN luminosity and outflow parameters arise from complex interplay between black hole masses and AGN Eddington ratios, and suggest how these properties can help us better understand the distribution of AGN Eddington ratios in galaxies with known large-scale outflows.

Speaker: Kastytis Zubovas (Center for Physical Sciences and Technology)

15 Panel of 4

16:10 COFFEE

Talks: AGN 1

Convener: Meredith Powell

16 Invited Talk

Speaker: Cristina Ramos-Almeida

17 Cosmic Ray Feedback in the Universe: Fermi Bubbles and Odd Radio Circles

Relativistic jets emanating from active galactic nuclei (AGNs) play a pivotal role as a feedback mechanism in the Universe, and the cosmic rays (CRs) carried by AGN jets can have profound influence on galaxy properties and the circumgalactic medium. Consequently, self-consistent modeling of CR propagation, spectral evolution, and emission mechanisms is imperative for understanding the thermal and non-thermal emissions of galaxies. We employ advanced 3D CR-magnetohydrodynamic simulations to elucidate that the multi-wavelength observations of the Fermi and eRosita bubbles within the Milky Way can be accounted for by past activity of Sgr A*. We investigate the feasibility of generating symmetric bubbles through the interaction of oblique AGN jets with the dense Galactic disk. Furthermore, we examine the potential for detecting Fermi bubble analogs in nearby galaxies, considering both hadronic and leptonic scenarios. We posit that, when viewed head-on, AGN jet-inflated bubbles may provide a plausible explanation for the recently identified enigmatic odd radio circles (ORCs). These works advance our understanding of CR jet feedback and their influence on various astrophysical phenomena within our cosmic neighborhood.

Speaker: Hsiang-Yi Karen Yang (National Tsing Hua University)

18 Global energetics and feedback as probed by AGN incidences

In this talk, I will show how the study of AGN incidence distributions is a powerful tool to understand the global energetics of AGN feedback. We use the complete, spectroscopic GAMA09 survey (z<0.4) to measure the fraction of galaxies hosting radio and X-ray AGN, defined using LOFAR and eROSITA data, as functions of mass-scaled power indicators. We recover the previously found mass-invariant triggering and fueling mechanisms in the incidence of X-ray AGN as a function of λEdd (∝ X-ray luminosity/stellar mass). However, the story is more perplexing in the case of radio AGN, as the incidence of radio AGN as a function of mass-scaled kinetic power (∝ jet power/stellar mass) shows a mass and jet power dependence. In fact, we find that radio morphology (compact vs complex) strongly affects the radio AGN incidence. These differences translate directly to the ways in which these AGN feed back energy to their host galaxies and halos. We quantify this by computing, for the first time, the average jet power for the population of massive galaxies as a function of stellar mass and radio morphology. We show that jet kinetic feedback dominates over any plausible inventory of radiatively-driven feedback for massive galaxies in the local universe. We also show, by comparing the average jet kinetic energy to the galaxy/halo binding energy, that radio AGN cannot fully unbind their host galaxies nor host halos. However, they have enough energy to impact the global thermodynamical heating and cooling balance in small halos and significantly contribute to offsetting local cooling flows in even the most massive clusters cores. Importantly, this work provides a clear observational benchmark to calibrate AGN feedback simulations. Lastly, since much of our knowledge about AGN accretion and feedback has been limited to massive galaxies, I give a brief outlook on how eROSITA can be used to study the low-mass regime, including X-ray emitting intermediate mass black holes in local dwarf galaxies.

Speaker: Zsofi Igo (Max Planck Institute for Extraterrestrial Physics)

19 Multi-scale Simulations of Supermassive Black Hole Accretion and Feedback from Galactic to Event Horizon Scales

The profound influence of supermassive black holes (SMBHs) on their host galaxies includes altering the orbits of stars, regulating star formation, modifying gas distribution, to name a few. To understand these processes we need to first understand how SMBHs grow through gas accretion and their associated feedback into the surrounding environment. These factors remain a current crucial challenge in astrophysics.

To better understand the fueling of supermassive black holes from galactic (tens of kiloparsec) to event horizon scales (milliparsec), we set up a suite of general relativistic magnetohydrodynamic multi-scale simulations by using the Athena++ code with GPU support through the Kokkos library. We include a variety of physical processes: radiative cooling, heating, turbulence, and magnetic fields.

On event horizon scales, modeling of accretion flows is limited in part by a dependence on ad-hoc initial conditions (ICs). While most simulations use idealized ICs, we employ massive elliptical galaxies from the IllustrisTNG project. We select a total of $\sim10$ central galaxies hosted by $M > M_{200}^{z=0} > 8 \times 10^{11}M_\odot$ halos. We extract their gas properties, magnetic field and gravitational potential from the unstructured moving-mesh of the IllustrisTNG simulations, using a 2nd order voronoi method to project these quantities onto a nested cartesian-mesh. The mesh is progressively refined with a total of 22 levels of mesh refinement towards smaller radii to resolve the event horizon. This way we resolve the thermodynamics of the multiphase gas and the magnetic structure across all scales during the accretion process. By connecting physics at multiple scales, our approach aims to bridge the gap between the galactic scale and the event horizon for SMBHs in elliptical galaxies.

We compare the SMBH mass accretion rates, angular momentum, magnetic flux and jet power as given by our simulations to those of IllustrisTNG for a range of galaxy masses and redshifts. This allows us to provide a comprehensive sub-grid model of black hole accretion and feedback for large-scale galaxy formation cosmological simulations. Additionally, we analyze the disk stresses and angular momentum transfer and provide mock observations of the multiphase gas from different angles, enabling direct comparisons with observational data.

Speaker: Miha Cernetic (The University of Chicago)

20 Panel of 4

Tuesday, 15 July

Registration

Talks: CGM 1

Convener: Cassandra Lochhaas (Center for Astrophysics | Harvard & Smithsonian)

21 Invited Talk

Speaker: Max Gronke

22 Connecting the turbulent circumgalactic medium to star formation in galaxies

The CGM and IGM contain fuel for future star formation and a record of past feedback. They are uniquely sensitive to the physics of baryonic flows. Diffuse, ionized plasmas such as the CGM are expected to be turbulent, because of the expected high Reynolds number. The presence and magnitude of this turbulence have profound implications for the sources that drive the thermal and dynamic properties of the gas. This presentation will delve into recent empirical findings on the turbulent CGM around galaxies of different start formation histories and quasars. Combining high-resolution absorption spectroscopy and deep galaxy survey data from the Cosmic Ultraviolet Baryon Survey (CUBS) enables spatially and spectrally resolved studies of the density structures, patchy chemical enrichment, and turbulent energy cascade in the multiphase CGM. The discussion will also touch upon expanding this study to high redshift and its connection to CGM properties at z>6 uncovered by the JWST, using new data from the upcoming Cycle 31 Large Program, Circumgalactic Observations of Nuv-shifted Transitions Across Cosmic Time (CONTACT).

Speaker: Hsiao-Wen Chen (The University of Chicago)

23 The spatial variations of circum-galactic gas structures in high resolution simulations and in state-of-the-art IFU observations

Gas flows in and out of galaxies are typically probed by quasar absorption lines which are usually limited to a single sightline through the halo, giving no information on the spatial structure of the gas probed in absorption. First studies using lensed, multiple or extended background objects have shown that there can be significant variation of absorber strengths on relatively small (~kpc and less) scales, hinting at an inhomogeneous clumpy circum-galactic medium. I will present our theoretical understanding of the CGM small-scale structure from high resolution cosmological zoom-in simulations and its impact on observables. Additionally I will report on our ongoing efforts of mapping the CGM in absorption using multiple background sources in deep (141 h) MUSE observations to characterize the spatial distribution and variation of cool gas in individual maps of the CGM of ~150 foreground galaxies.

Speaker: Ramona Augustin (AIP)

24 Multiphase gas in cosmological galaxy formation simulations

The gas cycle in and around galaxies is key to their evolution. Cosmological simulations have made enormous progress over the past decade in coming up with effective models for galaxy formation, unifying the Lambda cold dark matter cosmological model with the theory of galaxy formation. Yet, these simulations still struggle to accurately represent warm and cold gas and its cycling in space and thermodynamic state. This is a significant limitation to the predictive power of cosmological simulations since they are unable to provide predictions to emission and absorption features from these colder gas phases, e.g. in galactic outflows. In this talk, I will present a novel way to overcome this limitation without the need to explicitly resolve individual cold clouds. Using a multi-fluid approach, I will demonstrate how the unresolved interactions of cold clouds with the surrounding medium can be coarse-grained either from isolated high-resolution simulations or through fitting model parameters to observational data. I will also show how this modeling technique can resolve some of the long-standing challenges in cosmological galaxy simulations such as the self-consistent launching of outflows from the interstellar medium without the employment of numerical tricks such as hydrodynamical decoupling, burstiness or delayed cooling.

Speaker: Rainer Weinberger

25 Panel of 4

10:40 COFFEE & POSTER

Talks: SN & ISM 2

Convener: Matt Orr (Flatiron Institute & Rutgers University)

26 Invited Talk

Speaker: Lucia Armilotta

27 Observational constraints on the coupling efficiency of mechanical stellar feedback

Massive stars in star-forming regions inject huge amounts of energy and momentum into the ISM, producing ubiquitous superbubbles, turbulent gas motions and outflows. The coupling efficiency of mechanical stellar feedback and its dependence on metallicity remains uncertain in simulations. High angular resolution observations with integral-field spectrographs (e.g., MUSE), combined with the observations from HST and JWST, allow us to quantitatively compare the energetics of the expanding superbubbles and turbulent motions in ISM, with the star clusters and individual massive stars providing the energy for the observed supersonic gas motions. I will present our recent findings from such observational measurements of the coupling efficiency of mechanical stellar feedback in nearby galaxies. In particular, our results are indicative of a metallicity dependence of the kinetic energy of the feedback-driven structures in the ISM and a significant contribution of pre-SN feedback in their formation.

Speaker: Oleg Egorov (Heidelberg University)

28 What regulates the star formation rates in galaxies?

Understanding what regulates star formation in galaxies is a fundamental question in astrophysics. However, a simple estimate of the star formation rate (SFR) that a galaxy like ours should have overpredicts the observed SFR by nearly two orders of magnitude. Over the past 50 years, three main explanations have been proposed to account for these low observed SFRs: magnetic fields, turbulence, and stellar feedback. While it is likely that all three mechanisms play some role, their relative contributions to regulating the SFR remain a subject of debate.
Stellar feedback appears to produce SFRs consistent with observations for Milky Way-type galaxies. However, it is far less clear whether stellar feedback alone can explain the SFR in gas-rich galaxies.
In this talk, I will present a new analytical model based on gravo-turbulent theory to compute the SFR. This model, which has been rigorously tested against a series of numerical simulations, includes turbulent dispersion and predicts that when the size of the system is smaller than the turbulent Jeans length, the SFR is significantly reduced.
This model, which can be used as a subgrid model in large-scale simulations that do not resolve the small-scale interstellar medium, provides a clear explanation of how turbulence, in conjunction with stellar feedback, may contribute to regulating star formation in galaxies.

Speaker: Patrick Hennebelle

29 Modeling the multi-phase ISM shaped by star formation and feedback in the LMC

The small-scale processes of star formation and feedback are tightly linked to galaxy evolution through a multi-scale matter cycle. During this cycle, stars form from the interstellar medium (ISM), and reshape it by injecting energy, momentum and metals, completing a feedback loop. The duration and the efficiency of the successive stages of this cycle vary across and within galaxies, but the exact physical mechanisms driving it remain elusive. A detailed understanding of the small-scale mechanisms regulating star formation and feedback is the key for a full comprehension of galaxy evolution. Increasingly detailed ISM models and multi-wavelength observations now enable us to build a comprehensive view of this multi-scale cycle. As our nearest neighbor, the Large Magellanic Cloud (LMC) has been observed in a broad range of wavelengths and offers the perfect combination between high spatial resolution and a large field of view. It is the ideal laboratory to examine in detail the interplay between stellar activity and the ISM.
I will present a detailed study of the multi-phase ISM of the LMC using multi-wavelength tracers (including Halpha, OIII, SII, HI, 24 μm, CO), tracing all phases of the ISM, from the ionised to the molecular gas. By using MULTIGRIS, a new Bayesian code designed to constrain multi-component ionization models, I have determined key physical parameters of HII regions (e.g., density, ionization parameters, escape fractions of ionizing photons). Leveraging high spatial resolution observations of the LMC, we are now able to connect, for the first time, the multi-phase ISM structure of individual regions with their evolutionary timeline. This enables us to characterize the mechanisms driving star formation and feedback as a function of the local physical properties. Understanding how the detailed physical processes driving this cycle on ~10pc scales regulate the global, galactic-scale properties will serve as a major reference for high-redshift galaxy studies, where spatial resolution is far more limited.

Speaker: Xinyue Liang (Institute of Theoretical Astrophysics, University of Heidelberg)

30 Panel of 4

13:00 LUNCH

Discussion: SN+ISM and CR+Rad

31 SN + ISM

Speakers: Eva Schinnerer, Patrick Hennebelle

32 CR + Rad

Speakers: Ellen Zweibel (University of Wisconsin-Madison), Joakim Rosdahl (CRAL, France)

16:25 COFFEE

Discussion: Simulation challenges and Connecting scales

33 Simulation challenges

Speakers: Christoph Pfrommer (Leibniz-Institut für Astrophysik Potsdam (AIP)), Volker Springel

34 Connecting scales

Speakers: Andrey Kravtsov (The University of Chicago), Marcus Brüggen

Wednesday, 16 July

Talks: Winds 2

Convener: Alankar Dutta (Max Planck Institute for Astrophysics)

35 Invited Talk

Speaker: Crystal Martin (UC Santa Barbara)

36 Insights from High-Resolution QED Simulations- Metal transport and Outflow properties

Galactic-scale outflows, driven by supernova feedback in Milky Way-mass galaxies, play a crucial role in transporting metals from the disc to the circumgalactic medium (CGM). The distribution of these metals across different temperature phases within multiphase outflows is key to understanding CGM enrichment, as metal loading varies between phases. High-resolution, idealized simulations of Milky Way-like systems are essential for capturing the metal transfer between these phases.
In this talk, I will present results from the QED suite of 3D HD tall-box simulations, run using the GPU-accelerated HD code Quokka. With a $\sim$pc-scale resolution over a $\sim 10$ kpc$^3$ volume, QED simulations track metal exchanges between outflow phases with unprecedented detail. Our results show that while SN-driven outflows are responsible for expelling the majority of metals from the disc, the flux from freshly produced metals accounts for only half of the total metal flux. I will also share results from our latest paper that explores how environmental factors—such as initial gas surface density and galaxy metallicity—modulate wind properties and therefore metal transport.
Finally, I will share insights gained from generating mock X-ray observations of the QED simulations, highlighting how incomplete metal mixing between the phases leads to gradients manifested in Chandra observations.

Speaker: Aditi Vijayan (Australian National University)

37 Unveiling the Secrets of High-Velocity Outflows of the LMC's 30 Doradus Starburst

Starburst regions in a galaxy are the primary source of stellar-driven winds, which contribute to regulating the star-formation cycle. We investigate the properties of the gas distribution, kinematics, and ionization conditions of the near-side outflow along eight sightlines that reside in the 30 Doradus region of the LMC using UV absorption-line and H I 21-cm radio emission-line observations. We find that within 0.52 degrees from the center of 30 Doradus, the wind reaches maximum speeds of 100-165 km/s from the LMC's disk. The total integrated column densities of low-ions in the blueshifted wind are highest near the center of this starburst region and decline radially outward. We estimate an outflow mass of M ~ (5.7-8.6) x 10^5 Mⵙ, outflow rate of (dM/dt) ≳0.02 Mⵙ/yr, and mass loading factor of ≳0.10 for this region. The observed ion ratios, together with photoionization modeling, reveal that this wind is roughly 40-97% photoionized. We also estimated the metallicities and dust depletion patterns of two of the high-velocity absorbers and found one being consistent with a LMC origin and the other with a MW. The high-ion lines are broader and exhibit kinematic offsets compared to the low-ions, indicating the presence of turbulent mixing layers within the wind. Finally, our hydrodynamical simulations of the Magellanic Clouds (MCs) and MW system suggest that the Magellanic Corona can protect the LMC winds from the ram-pressure forces exerted by the MW's halo.

Speaker: Suraj Poudel (Texas Christian University)

38 Mapping circumgalactic outflows with MUSE

I present the first statistical study of circumgalactic outflows mapped through MUSE observations of Mg II 2796, 2803 emission, revealing extended halos that span several tens of kiloparsecs from their host galaxies. These observations herald a significant advance for deciphering the role of feedback processes in regulating galaxy evolution. Our analysis combines deep MUSE observations with an outflow modeling framework to interpret the kinematics and geometry of Mg II halos. This framework was initially applied to a spectacular Mg II emission halo around a star-forming galaxy recently discovered by us in the Hubble Ultra Deep Field, featuring a prominent P-Cygni spectral profile and an emission halo extending out to at least 30 kpc. We have now become able to expand our approach to a much larger sample of ~40 galaxies at $0.7

Speaker: Ismael Alejandro Pessa Gutierrez (AIP)

39 Panel of 4

10:40 COFFEE & POSTER

Talks: CGM 2

Convener: Ramona Augustin (AIP)

40 Invited Talk

Speaker: Céline Péroux (ESO)

41 Mix, Cool, Repeat: Understanding the dynamics of a turbulent & magnetised CGM

Galaxies interact with their surrounding circumgalactic medium (CGM) through complex feedback mechanisms that regulate their evolution. The CGM, like other astrophysical media, is a turbulent, magnetised environment where mixing processes and radiative cooling drive the formation of multiphase gas. Understanding this multiphase nature is crucial for understanding the baryon cycle, yet the vast range of length scales involved makes resolved simulations at cosmological scales computationally prohibitive.

Subgrid models, inspired and verified with small-scale idealised simulations, offer a powerful approach to bridge this gap, capturing unresolved multiphase interactions and their role in galaxy evolution. In this talk, I will present our recent work on understanding multiphase gas evolution, with turbulence, magnetic fields, 3-phase gas, and thermal instability, highlighting key differences between mixing layer simulations and turbulence box simulations. I will then introduce our project MOGLI aimed at leveraging insights from these idealised studies to develop a subgrid multifluid model within the moving-mesh hydrodynamic code AREPO. This model enables the exploration of multiphase gas evolution at scales previously inaccessible in large-scale simulations. I will discuss the implementation details and demonstrate how this framework advances our ability to model feedback and gas dynamics in galaxy formation.

Speaker: HItesh Kishore Das (Max Planck Institute for Astrophysics, Garching)

42 Cosmic Ray Feedback-Driven Evolution of Cold Gas in the Circumgalactic Medium

The circumgalactic medium (CGM) is the nexus of galaxy formation. Fresh gas that fuels star formation must pass through the CGM to reach the interstellar medium, while material accelerated by feedback and expelled from galaxies builds up a gaseous reservoir in the CGM. Observations reveal vast amounts of cold gas in the CGM, yet the processes that shape its dynamics remain uncertain. Condensation powered by the thermal instability is able to generate cold gas clouds in situ but can be offset by feedback processes. Cosmic rays (CRs), a key component of non-thermal galactic feedback, impact cold gas clouds by heating and exerting pressure, which can slow the inevitable condensation process. We present the results of a dedicated simulation set that tries to shed light on the role of CRs in the formation and the life of cold gas clouds in the CGM. We show that the impact of CRs on the thermal instability highly depends on the details of CR transport and highlight that fast CR transport allows for a quick escape of CRs from forming cold clouds, diminishing their stabilizing effect, and allowing clouds to collapse more readily. Furthermore, we also emphasize the importance of high numerical resolution in studying the interactions of CRs and the multiphase CGM by demonstrating that insufficiently resolved simulations exaggerate CR–mediated effects.

Speaker: Matthias Weber

43 Finding the circumgalactic medium in the Lyman-alpha forest

Studying the circumgalactic medium (CGM) is a challenge, particularly at the key epoch prior to Cosmic Noon ($z > 2$), where galaxies samples remain very small. However, there is an abundance of Lyman-alpha forest data that contain a wealth of information about the conditions present in this medium.

Morrison et al (2024) showed that a new class of CGM absorption should be studied: Strong Blended Lyman-alpha (SBLA) absorbers. We explore the nature of the relationship between strong blends of Lyman-alpha absorption and halos using the TNG50 simulation. In doing so we have extended and generalized the identification of halos in the forest. We show that we are able to transform the Lyman-alpha forest into a powerful halo finding machine for not only identifying CGM regions but also estimating their host halo masses.

Speaker: Duarte Muñoz Santos (Laboratoire d'Astrophysique de Marseille)

44 Panel of 4

13:00 LUNCH

14:25 Conference photo

Talks: CRs & Magnetic Fields

Convener: Allison Matthews (Carnegie Observatories)

45 Invited Talk

Speaker: Philipp Girichidis (Heidelberg University)

46 Constraining Cosmic Ray Feedback in Galaxy Formation

Cosmic rays (CRs) are ubiquitous in the interstellar medium (ISM) of the Milky Way and nearby galaxies and are thought to play an essential role in governing their evolution. However, many of their properties remain poorly constrained. Since direct measurements of CRs are limited to our local environment, observations of radio and gamma-ray emission arising from CRs provide a powerful tool to constrain their transport properties and interactions with the ISM and magnetic fields in other galaxies. To better understand the link between observational signatures and CR physics, we use a series of magneto-hydrodynamical simulations with AREPO that include self-consistent CR physics, complemented by post-processing to model CR spectra and their multi-frequency emission. These simulations have enabled us to identify the processes required to simultaneously reproduce observed correlations and spectra of star-forming galaxies in the radio and gamma-ray regimes. Building on this, I will show first results of applying this framework to cosmological zoom simulations within the Auriga galaxy formation model, targeting dwarf to Milky Way-sized galaxies and their satellites to explore how environmental factors — such as magnetic field strengths and host interactions — impact CR-related observables. In particular, I will assess how well the commonly used relation between the gamma-ray emission and star formation rate of galaxies can help us to constrain CR transport parameters at the low-mass end, which has important consequences on constraining CR feedback and its implications for galaxy evolution. Additionally, by incorporating more detailed modelling of CR electrons and tracking their spectral evolution in time, I will assess the validity of the steady-state assumption commonly used in interpreting radio and gamma-ray observations. This will allow us to evaluate how these assumptions influence our understanding of the underlying CR physics and magnetic field properties and provide an invaluable link between theory and observations.

Speaker: Maria Werhahn

47 How magnetic fields alter feedback and angular momentum transfer in MW-like galaxies

In previous work, we have shown that magnetic fields are fundamental to the evolution of MW-like galaxies. Specifically, in the Auriga model, magnetohydrodynamic (MHD) simulations produce realistic galaxies with spiral arm structure and radially-extended discs, whilst their hydrodynamic counterparts are systematically smaller, and exhibit bar and stellar ring features not observed in nature. In this talk, I will show how magnetic fields produce this difference by modifying the transport of angular momentum. This has myriad effects including: the suppression of bar instabilities, the re-shaping of star formation sites, and an increased growth of the central black hole. Together, these effects act to switch the dominant channel of feedback from stellar- to active galactic nuclei (AGN)-driven. In turn, this substantially impacts the evolution of the circumgalactic medium (CGM). In the last part of my talk, I will discuss the applicability of our results to other galaxy formation models, and explain why our results cannot be replicated by the tuning of feedback models alone.

Speaker: Joseph Whittingham (AIP)

48 Towards reliable simulations of magnetic fields in galaxies

It is generally believed that the magnetic dynamo in galaxies is a key factor in amplifying small cosmic seed fields to the strengths observed today, both within galaxies and in the CGM/IGM. While simulations with MHD have generally shown modest changes of the overall star formation, magnetic fields are a key factor in the propagation of cosmic rays and their effect on the cloud-scale physics remains to be explored in greater detail. However, the results of MHD simulations of galaxies are notoriously sensitive to small-scale dynamo contributions and to numerical issues such as the zero-divergence constraint, which has led to some notable contradictions in the literature. I will present a systematic comparison of the galactic dynamo in AGORA-type simulations with different MHD codes and solvers. By zooming deep into particular regions of a galaxy and into cosmological boxes, we hope to understand how magnetic fields change the small-scale collapse of clouds and the larger-scale fields in the IGM. At the Thinkshop, my goal is to learn from (and connect with) researchers in the areas that affect, or are affected by, magnetic fields, such as ISM turbulence and cosmic ray feedback.

Speaker: Benedikt Diemer (University of Maryland)

49 Panel of 4

16:10 COFFEE

19:00 DINNER

Thursday, 17 July

Talks: High-z 1

Convener: Enrico Garaldi (Kavli Institute for Physics and Mathematics of the Universe)

50 Invited Talk

Speaker: Sandro Tacchella (KICC, University of Cambridge)

51 Galaxy formation at sub-parsec resolution

Large-scale cosmological simulations of galaxies like IllustrisTNG have been enormously useful at providing quantitative insights on galaxy evolution, especially after the end of Reionization. However, their limited numerical resolution and, crucially, their crude implementations of the physics of star formation, of stellar feedback, of cold gas and of the interstellar medium makes them less applicable to provide theoretical guidance onto how galaxies form and evolve in the first billion year of the Universe history. In this talk, I will present our efforts to simulate galaxies in the full cosmological context with a new model that includes multi-phase gas with non-equilibrium primordial chemistry down to 10 K, explicit energy injections from exploding supernova, stellar ionizing and non ionizing radiation and hence photoionization feedback and photoelectric heating, and star formation based on a Jeans-instability criterion and constant efficiency per free-fall time. This model is designed for ultra-high resolution simulations, reaching mass scales of actual individual stars. We will present first results from simulated galaxies at 20-200 solar-mass resolution (~1000 x better than TNG50) and with sub-parsec spatial resolution of the gas. I will focus on scientific results at z>5-6 and on what these simulations are telling us about the formation of very dense and very compact stellar systems in the early Universe and on how star formation may proceed across a variety of galactic environments.

Speaker: Annalisa Pillepich (Max Planck Institute for Astronomy)

52 Galaxy assembly in the first billion years: Mini-quenching, lulling galaxies and more evidence for bursty SFHs driven by intense feedback

Directly observing the first quenched galaxies and understanding the feedback mechanisms that shaped their star-formation histories (SFHs), quenching and baryon cycles is crucial for constraining galaxy formation models. Prior to JWST, quenched galaxies were only identified up to z < 4, and high-redshift (z > 3) quenched galaxies were exclusively massive (M⋆ > 10^10 M⊙). JWST has now pushed this frontier to z ~ 7–8, uncovering a surprising diversity: not all quenched systems at these epochs are massive.

The SFHs of so-called "mini-quenched" galaxies suggest rapid and recent quenching on timescales of tens of Myr. Their quenching is likely driven by internal feedback mechanisms, such as outflows triggered by intense star formation or accreting black holes, which expel the ISM and halt star formation. Afterwards, renewed gas inflows may lead to rejuvenation, consistent with bursty SFHs through stochastic baryon cycles, as predicted by simulations of early galaxies. Additional evidence for bursty SFHs comes from scatter around the MS and variations in star formation rates across different timescales.

To test this theoretical framework and establish the feedback mechanisms which drive bursty star formation, I will present the first results from a novel deep 74-hour JWST-NIRSpec survey designed to investigate bursty star formation through SFH and ISM studies. Our program targets a diverse sample of high-z galaxies in all stages of star formation, crucially including faint and previously under-represented mini-quenched and "lulling" galaxies (i.e., those with low specific star formation rates below the MS).

I will highlight how mini-quenched and lulling galaxies offer unique insights, as their stellar populations and ISM are imprinted with their past assembly histories. In particular, I will present the first study of the ISM conditions in lulling galaxies, using a sample of ten such systems at z > 5, for which I will examine the ionization state and metallicity of the residual gas and explore whether the ionization is driven by residual star formation, AGNs, or shocks.

Finally, I will show how our program quantitatively constrains bursty SFHs, illuminates the transition from temporary quenching and episodic star formation to permanent quenching and secular evolution, and paves the way for future JWST studies on feedback-regulated star formation at high redshifts.

Speaker: Tobias Looser (Harvard University)

53 Exploring the Impact of Different Stellar Feedback Scenarios on ISM Structure and Spectroscopic Observables with MEGATRON

Various solutions have been proposed to solve the high-redshift `bright galaxy problem', such as more efficient star formation, more bursty star formation, and top heavy initial mass functions. While equally interesting, each scenario must also differ in how these stellar populations couple to the interstellar medium (ISM) through stellar feedback. In this talk, I will present first results from the MEGATRON suite of high-resolution cosmological radiation hydrodynamics zoom simulations which for the first time feature non-equilibrium chemistry and heating/cooling processes coupled to on-the-fly radiative transfer. Along with this physics, each simulation also includes detailed feedback prescriptions for population II and III stellar winds, supernovae, and hypernovae, coupled to the different star formation models implied by each scenario.

Using this data, I will discuss the impact that these three star-formation scenarios have on the phase structure of the ISM. Furthermore, using the unique capabilities of the simulations, I will trace these differences through to their impacts on direct observables, such as UV luminosity functions, line ratios and diagnostic diagrams, C/O and N/O abundances and the mass-metallicity relation. At each step, I will contextualize results with the latest JWST observations. All of this will begin to build directly falsifiable predictions through quantities which are already being directly measured at high-redshift with JWST.

Finally, I will advertise a novel approach for the sub-grid modeling of magnetized AGN jets for cosmological simulations, hoping to spark further discussions.

Speaker: Nicholas Choustikov (University of Oxford)

54 Panel of 4

10:40 COFFEE & POSTER

Talks: Low-z 1

Convener: Kirsten Hall (Center for Astrophysics | Harvard & Smithsonian)

55 Invited Talk

Speaker: Kathryn Kreckel (Heidelberg University)

56 Regulation of star formation in low-metallicity galaxies by feedback and turbulence

There is ample empirical evidence that galaxies’ star formation efficiency is nearly universal even across a wide range of galactic environments and metallicities. We use a suite of high-resolution hydrodynamics simulations of isolated galaxies at different metallicities to study how the cold, dense interstellar medium and star formation rate vary as a function of chemistry, ionizing radiation field strength, and smaller scale density fluctuations. We find that although the molecular hydrogen fraction depends sensitively on the local metallicity and far UV flux, the star formation efficiency per free-fall time does not. The simulations indicate that this universality arises due to the interplay between turbulent compression of gas and its subsequent dispersion due to feedback.

Speaker: Ava Polzin (The University of Chicago)

57 The impact of feedback on the cool gas around star-forming galaxies

The cool gaseous halos around galaxies hold some of the keys in understanding feedback and galactic winds. This cool halo gas can be best studied with background quasars, which are very sensitive probes of not only its presence, but also of its kinematics. With a sample of more than 100 galaxy-quasar pairs from the Megaflow survey, I will present the latest constraints on the metal distribution, the kinematics of the cool gas in the circum-galactic medium in relation to the galaxy host properties. We will discuss the impact of our results on our understanding of feedback processes.

Speaker: Nicolas Bouche (CRAL)

58 Prevention is better than cure?

Many cosmological simulations typically rely on highly mass loaded, ejective winds, particularly for low mass galaxies, to regulate star formation. Recent hints from observations, analytical theory, and idealised simulations have pointed towards lower mass loadings, and a more preventative form of feedback. Using the Arkenstone winds framework, for the first time we model the impact of low mass, high specific energy winds in a cosmological context, leading to many interesting implications for the growth and evolution of galaxies and their surrounding gas.

Speaker: Jake Bennett (Center for Astrophysics | Harvard & Smithsonian)

59 Panel of 4

13:00 LUNCH

Discussion: Low-z and CGM

60 Low-z

Speakers: Natascha Förster-Schreiber (Max Planck Institute for Extraterrestrial Physics), Yohan Dubois (Institut d'Astrophysique de Paris)

61 CGM

Speakers: Jonathan Stern (Tel Aviv University), Lutz Wisotzki (AIP)

16:25 COFFEE

Discussion: High-z and AGN

62 High-z

Speakers: Ewald Puchwein, Giacomo Venturi (Scuola Normale Superiore)

63 AGN

Speakers: Debora Sijacki, Tanya Urrutia (Leibniz Institut für Astrophysik, Potsdam)

Friday, 18 July

Talks: AGN 2

Convener: Rosie Talbot

64 Invited Talk

Speaker: Tiago Costa (Newcastle University)

65 Unveiling Turbulence Drivers in Quasar Halos: Insights from IFS Observations with VLT/MUSE and JWST/NIRSpec IFU

The recent advent of high-throughput integral-field-unit spectrographs (IFS) has enabled unprecedented sensitivity in mapping low-density gas, opening new avenues for probing the dynamical states of the interstellar and circumgalactic medium (ISM and CGM). In this talk, I will present an investigation into turbulence and energy injection mechanisms in luminous quasar halos across redshifts 0.5<z<3, leveraging data from VLT/MUSE and JWST/NIRSpec IFU. By analyzing velocity structure functions (VSFs) of the extended ISM and CGM, we demonstrate how AGN-driven outflows and jet-induced bubbles primarily inject energy at scales <10 kpc, while larger-scale processes such as tidal interactions and galaxy mergers dominate energy injection further away from the central engine. In addition, elevated VSF amplitudes near halo centers reveal a stronger influence of AGN feedback in these regions. However, the overall turbulent energy contained in gas motions is subdominant in comparison to the quasar bolometric luminosity, suggesting inefficient energy coupling between quasar radiation and gas dynamics. These findings provide empirical constraints on the scale-dependent mechanisms of energy injection and feedback in quasar environments, offering new insights into their role in shaping galaxy evolution across cosmic time.

Speaker: Mandy Chen

66 Constraining AGN Feedback with Microwave and X-ray Measurements

Feedback from active galactic nuclei (AGN) plays an essential role in current models of galaxy formation, yet the details of this process remain extremely uncertain. I will describe our work combining numerical simulations with microwave and X-ray observations to better constrain this process. Our team has conducted a series of simulations covering a broad range of feedback properties. At microwave wavelength, we are applying them to make predictions of the thermal and kinetic Sunyaev-Zel’dovich effects. We have compared these with stacked data from the Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT) to derive AGN feedback constraints, and we describe our plans to improve these limits with the TolTEC camera on the Large Millimeter Telescope (LMT). At X-ray wavelengths, we are using the simulations to make predictions of soft X-ray emission, and comparing them with stacked eROSITA observations. At the AIP Thinkshop, we hope to stimulate a lively and productive discussion on how such comparisons can best be applied to inform the design of future observational surveys and provide new insights into the history of AGN feedback.

Speaker: Evan Scannapieco (Arizona State University)

67 The XMAGNET Exascale MHD simulations of SMBH feedback in galaxy groups and clusters

We present initial results from extremely well-resolved 3D magnetohydrodynamical simulations of idealized galaxy clusters, conducted using the AthenaPK code on the Frontier exascale supercomputer. These simulations explore the self-regulation of galaxy groups and cool-core clusters by cold gas-triggered active galactic nucleus (AGN) feedback incorporating magnetized kinetic jets. Our simulation campaign includes simulations of galaxy groups and clusters with a range of masses and intragroup and intracluster media properties. Here, we present results that focus on a Perseus-like cluster. We find that the simulated clusters are self-regulating, with the cluster cores staying at a roughly constant thermodynamic state and AGN jet power staying at physically reasonable values (≃ $10^{44}$ − $10^{45}$ erg/s) for billions of years without a discernible duty cycle. These simulations also produce significant amounts of cold gas, with calculations having strong magnetic fields generally both promoting cold gas formation and allowing cold gas out to much larger clustercentric radii (≃ 100 kpc) than simulations with weak or no fields (≃ 10 kpc), and has filamentary morphology. We find that AGN feedback significantly increases the strength of magnetic fields at the center of the cluster. We also find that the magnetized turbulence generated by the AGN results in turbulence where the velocity power spectra are tied to AGN activity whereas the magnetic energy spectra are much less impacted after reaching a stationary state.

Speaker: Philipp Grete (University of Hamburg)

68 Panel of 4

10:40 COFFEE

Talks: High-z 2

Convener: Sirio Belli (Università di Bologna)

69 Invited Talk

Speaker: Harley Katz (University of Chicago)

70 Variability of the UV luminosity function with SPIC

Since JWST began providing breakthrough results in July 2022, our understanding of early galaxy formation has been challenged. While HST enabled us to observe galaxies out to z ~ 10, JWST has pushed this boundary further, revealing an unexpected overabundance of massive galaxies at z > 10. This discovery challenges theoretical models, implying rapid evolution of dark matter halos during this epoch. One key topic that has attracted significant attention is the UV luminosity function (LF) of early galaxies for eg. the origin of its variability and boosted bright end. Among various explanations, the stochasticity of star formation stands out most promising. In this work, we investigate the impact of the star formation rate (SFR) variability on the LF of high-z galaxies using the suite of radiation hydrodynamic simulations “SPICE” (Bhagwat et al. 2024), which feature different implementations of supernova feedback, resulting in diverse star formation histories. I will discuss our immediate results extracted from these simulations. We also post-process SPICE to quantify the scatter in the MUV,1500 - Mhalo plane ie. σUV, as frequently cited in existing literature. Additionally, I will explore how these variabilities influence the morphologies of individual galaxies. I look forward to sharing these insights in my talk.

Speaker: Arghyadeep Basu (MPA, Garching)

71 Confronting Lyman alpha properties of high-z galaxies with simulations with strong stellar feedback

Lyman-alpha (Lyα) emission serves as a valuable probe of gas kinematics in and around galaxies. Observations of high-redshift galaxies frequently exhibit distinctive Lyα spectral features, often indicative of optically thick, neutral galactic outflows. However, the extent to which galaxy formation simulations can reproduce these observations remains an open question. We investigate this issue by analyzing both idealized and cosmological galaxy simulations run with different input physics. Our analysis focuses on two kinematic measures derived from Lyα line profiles and surface brightness profiles, and compares simulation results with observations of Lyα emitters. Simulations incorporating strong stellar feedback successfully reproduce Lyα profiles characterized by relatively weak outflow signatures. However, these simulations often struggle to produce optically thick, neutral outflows, including MHD simulations incorporating cosmic ray pressure. These results suggest that more work is needed to fully account for the observed diversity of Lyα spectral features in high-redshift galaxies.

Speaker: Taysun Kimm (Yonsei University)

72 The COLIBRE model of galaxy formation

The COLIBRE model of galaxy formation is the new flagship suite of simulations of the Virgo consortium. It builds upon years of development by a big team and is a substantial leap forward compared to the previous (and existing) generation of models. In brief, the key improvements are: (1) a modelling of the cold ISM phase, (2) a multi-grain, multi-size fully-coupled dust model, (3) the evolution of Hydrogen and Helium out of equilibrium, (4) the use of more resolution in the dark matter to suppress spurious heating (growth) of galaxies, (5) an upgraded physically-motivated multi-channel model for stellar feedback (6) a hybrid jet model for AGN, (7) an updated treatment of the evolution of globular clusters, (8) much-improved merger trees and structure identification, and (9) a model calibration strategy based on machine-learning techniques to inform the choices. This model is run in volumes substantially larger than previously available and at different resolutions allowing to connect high-redshift questions to late-time Universe surveys and precision cosmology.
In this talk, I will present the general model design and performance against observations at all redshifts, show results from the first series of papers published in the spring and discuss the role of the improved feedback model in shaping the galaxy population across cosmic time.

Speaker: Matthieu Schaller (Lorentz Institute & Leiden Observatory)

73 Panel of 4

13:00 LUNCH

Talks: Low-z 2

Convener: Matthieu Schaller (Lorentz Institute & Leiden Observatory)

74 Invited Talk

Speaker: Vadim Semenov (Harvard University)

75 Bursty Star Formation in Dwarfs is Sensitive to Numerical Choices in Supernova Feedback Models

Simulations of galaxy formation are mostly unable to resolve the energy-conserving phase of individual supernova events, having to resort to subgrid models to distribute the energy and momentum resulting from stellar feedback. However, the properties of these simulated galaxies, including the morphology, stellar mass formed and the burstiness of the star formation history, are highly sensitive to numerical choices adopted in these subgrid models. Using the SMUGGLE stellar feedback model, we carry out idealized simulations of a 𝑀vir ∼ 10^10 M⊙ dwarf galaxy, a regime where most simulation codes predict significant burstiness in star formation, resulting in strong gas flows that lead to the formation of dark matter cores. We find that by varying only the directional distribution of momentum imparted from supernovae to the surrounding gas, while holding the total momentum per supernova constant, bursty star formation may be amplified or completely suppressed, and the total stellar mass formed can vary by as much as a factor of ∼ 3. In particular, when momentum is primarily directed perpendicular to the gas disk, less bursty and lower overall star formation rates result, yielding less gas turbulence, more disky morphologies and a retention of cuspy dark matter density profiles. An improved understanding of the non-linear coupling of stellar feedback into inhomogeneous gaseous media is thus needed to make robust predictions for stellar morphologies and dark matter core formation in dwarfs independent of uncertain numerical choices in the baryonic treatment.

Speaker: Eric Zhang (University of California, Riverside)

76 Probing feedback and environments of radio quiet quasars with radio through sub-millimeter interferometry

Despite recent discoveries of quasar feedback in action through outflows and jets, the amount of energy that the active nucleus is capable of injecting into the extended medium of the host galaxy remains unknown. The most mysterious component of quasar feedback is the lowest density, hot volume-filling gas. Though there are tentative detections of this component via its thermal Sunyaev-Zel'dovich (SZ) effect, there is no consensus on how quasar winds are launched, how they become coupled to the host's interstellar medium, what is their physical extent into the circumgalactic medium, or how they are affected by environment and mergers. With targeted multi-wavelength interferometric observations from the VLA, ALMA, and the SMA, we report our recent results on the radio through sub-mm emission of two hyperluminous, radio quiet quasars and their companions/environments. Both targets have submm-only detected companions. One of our targets is an extremely luminous dual quasar system, with the second component heavily obscured and only detected at long wavelengths, and a third CO-detected merging companion. We find strong evidence for the tSZ effect due to the hot gas surrounding this system, and a possible large-scale halo tSZ detection around the other quasar system. We explore different scenarios for the origin of this hot gas, placing constraints on the total thermal energy output of the hottest component of quasar winds, and if confirmed, these will be only the second and third direct tSZ detections and at the highest redshifts to-date.

Speaker: Kirsten Hall (Center for Astrophysics | Harvard & Smithsonian)

77 A Novel Supermassive Black Hole Feedback Model in Hydrodynamical Simulations

In this talk, I will present the "Beyond" simulation project, a series of hydrodynamical simulations conducted using the AREPO code. I introduce a novel, physically motivated, approach to SMBH feedback, dynamically adjusting feedback efficiency and implementation based on the evolving properties of SMBHs.

The results reveal how this feedback mechanism shapes the properties of galaxies and halos across mass ranges, from dwarfs to clusters, and over cosmic epochs, from high redshift to the present. Importantly, we analyze feedback effects on scales ranging from the galactic scales to regions beyond the halo boundary, extending out to the closure radius. I evaluate these results through direct comparisons with observational data from galaxy surveys such as SDSS and DESI at low redshifts, and JWST at high redshifts, as well as gas observations from facilities like XMM-Newton, ALMA, and others. I highlight the role of SMBH feedback in regulating star formation, driving gas circulation, and reshaping gas distribution out to the closure radius.

Finally, I will discuss the implications of this feedback model for understanding galaxy evolution and its potential for future studies and collaborations.

Speaker: Mohammadreza Ayromlou (University of Bonn)

78 Panel of 4