ELVES IV: The Satellite Stellar-to-Halo Mass Relation Beyond the Milky-Way

TL;DR

This study uses a large sample of Local Volume satellite galaxies and semi-analytical modeling to better understand the stellar-to-halo mass relation for satellite galaxies, extending previous Milky Way-based analyses.

Contribution

It provides new constraints on the satellite stellar-to-halo mass relation using the largest Local Volume satellite sample and Bayesian model comparison, confirming previous Milky Way findings.

Findings

Best-fit relation: $M_\star \propto M_{\mathrm{peak}}^{2.10}$ with low scatter

Steeper slope model also consistent but not necessary

Satellite stellar-to-halo mass relation aligns with Milky Way results

Abstract

Quantifying the connection between galaxies and their host dark matter halos has been key for testing cosmological models on various scales. Below $M_\star \sim 10^9\,M_\odot$, such studies have primarily relied on the satellite galaxy population orbiting the Milky Way. Here we present new constraints on the connection between satellite galaxies and their host dark matter subhalos using the largest sample of satellite galaxies in the Local Volume ($D \lesssim 12\,\mathrm{Mpc}$) to date. We use $250$ confirmed and $71$ candidate dwarf satellites around 27 Milky Way (MW)-like hosts from the Exploration of Local VolumE Satellites (ELVES) Survey and use the semi-analytical SatGen model for predicting the population of dark matter subhalos expected in the same volume. Through a Bayesian model comparison of the observed and the forward-modeled satellite stellar mass functions (SSMF), we infer the satellite stellar-to-halo mass relation. We find that the observed SSMF is best reproduced when subhalos at the low mass end are populated by a relation of the form $M_\star \propto M^\alpha_\mathrm{peak}$, with a moderate slope of $\alpha_\mathrm{const}=2.10 \pm 0.01$ and a low scatter, constant as a function of the peak halo mass, of $\sigma_\mathrm{const}=0.06^{+0.07}_{-0.05}$. A model with a steeper slope ($\alpha_\mathrm{grow}=2.39 \pm 0.06$) and a scatter that grows with decreasing $M_\mathrm{peak}$ is also consistent with the observed SSMF but is not required. Our new model for the satellite-subhalo connection, based on hundreds of Local Volume satellite galaxies, is in line with what was previously derived using only the Milky Way satellites.