Relating the Diverse Merger Histories and Satellite Populations of Nearby Galaxies
Adam Smercina, Eric F. Bell, Jenna Samuel, Richard D'Souza

TL;DR
This study reveals a surprisingly tight correlation between the dominant merger history of nearby galaxies and their satellite populations, highlighting gaps in current galaxy formation models.
Contribution
It introduces a new empirical relation between merger history and satellite count, and compares it with simulations, exposing discrepancies in galaxy formation modeling.
Findings
A tight relation exists between merger history and satellite number in observed galaxies.
Current simulations do not reproduce the observed $M_{\rm\star,Dom}$-$N_{\rm Sat}$ relation.
Discrepancies suggest simulations lack diverse merger histories.
Abstract
We investigate whether the considerable diversity in the satellite populations of nearby Milky Way (MW)-mass galaxies is connected with the diversity in their host's merger histories. Analyzing 8 nearby galaxies with extensive observations of their satellite populations and stellar halos, we characterize each galaxy's merger history using the metric of its most dominant merger, , defined as the greater of either its total accreted stellar mass or most massive current satellite. We find an unexpectedly tight relationship between these galaxies' number of satellites within 150 kpc () and . This relationship remains even after accounting for differences in galaxy mass. Using the star formation and orbital histories of satellites around the MW and M81, we demonstrate that both likely evolved along the…
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