ELVES and Dwarfs: Elucidating Low-Mass Galaxies with the Exploration of Local VolumE Satellites Survey

Abstract

Low-mass, “dwarf” galaxies are ubiquitous probes of dark matter and galaxy formation physics. Many are found as satellites of more massive galaxies, like the Milky Way (MW). In fact, the dwarf satellites of the MW have long been a central observational benchmark for models of small-scale structure formation and dwarf evolution. However, it is critical to move beyond just the MW and consider the dwarf satellites of a statistically large sample of host galaxies. To do this, I developed the Exploration of Local VolumE Satellites (ELVES) Survey, which characterized the dwarf satellites of a volume-limited sample of 30 nearby massive, MW-like hosts.Progressing this survey involved developing specialized detection algorithms to find these faint galaxies and sophisticated distance measurement techniques to constrain the distances of the detections. This is important to confirm that the detected galaxies are actually satellites of a certain host and not contaminants along the line of sight. The end result is a census of the “classical” (i.e. M* > 10^5.5 M_sun) satellites of 30 hosts, roughly a 5x increase over the statistics previously available. With this expanded sample of hosts, I compared the observed satellite abundance to that predicted from galaxy formation models, finding good agreement. The observed satellite spatial distribution did not, however, agree well with predictions from current models. In terms of satellite abundance and spatial distribution, the MW appears remarkably typical among comparable systems. I performed an in-depth investigation into the structure of dwarf satellites and quantified various scaling relations that will be useful benchmarks for future galaxy formation simulations. Finally, I investigated the star cluster properties of these dwarf galaxies, uncovering an interesting dependence on the large-scale environment that the dwarf resides in. The survey presents a unique dataset that can be used to explore various other aspects of near-field cosmology and dwarf evolution.