IAUS379: Dynamical Masses of Local Group Galaxies

Since the early 2000s satellite dwarf galaxies of the Local Group and more recently, the nearby Centaurus A/M83 group, have been known to show morphological characteristics and spatial distributions that do not match predictions from ΛCDM simulations. In particular, satellite dwarf galaxies inhabiting the Local Group and the Centaurus A/M83 group appear to be co-rotating in confined disks known as satellite planes. ΛCDM simulations have failed to fully reproduce satellite planes despite increasingly advanced simulations, including baryon physics, and aren’t associated with galactic analogues of the local universe in ΛCDM simulations. Several presented hypotheses suggest that these apparent discrepancies may be the result of one of three mechanisms; that statistical bias in determinations of satellite planes in the local universe leads to inflated significance, that simulations fail to simulate some feature of the universe or that unique conditions in the local universe led to the formation of satellite planes. This is motivating an international effort to search for satellite galaxies and ultimately, satellite planes, outside of the local universe. Using the Hyper Suprime Cam from the Subaru telescope, we capture ~4 degree field of view images of nearby isolated L* galaxy environments with the intent of identifying satellite dwarf galaxies complete to an absolute g-band magnitude of >-10 and ultimately, identifying satellite planes. These environments reside outside of the Local Sheet, which may have provided the conditions that favours the generation of satellite planes, or the galaxies within may not form an independent sample which reduces the significance of satellite planes. Our recent research has focused on searching for the satellite galaxies of M104 and NGC2683, two mostly isolated galaxy environments that reside outside of the local sheet and are thus free from biases associated with it. Across these two environments, we find over 20 newly discovered highly probably dwarf galaxy candidates up to projected radii of 400 kpc, which for NGC2683 are distributed in an anisoptric, flattened disk and for M104, a lop-sided but circular disk. We intend to follow up these candidates with observations using IFU-M, a novel IFU spectroscope undergoing commissioning at the Magellan telescopes of the Las Campanas Observatory in Chile. These spectroscopic observations will confirm that our new galaxy candidates are associated with their assumed hosts, determine if co-rotation is present, and for brighter candidates, allow us to explore the mass-to-light ratios and star formation histories of these dwarf galaxies. This spectroscopically enhanced dataset of newly discovered dwarf satellite galaxies limits statistical bias and enables us to answer questions about the local universe and our cosmological models; is the local universe a cosmological oddity, or do our models of the universe fail to account for an unknown factor?