The Missing Satellite Problem in 3D

TL;DR

This study measures the satellite galaxy luminosity function around hosts of various masses up to redshift 1.5, revealing that current models do not consistently match observations across different conditions, indicating the need for improved physics in simulations.

Contribution

It provides the first measurement of faint satellite luminosity functions across a range of host masses and redshifts up to 1.5, testing and challenging existing galaxy formation models.

Findings

Models perform similarly overall but fail at certain redshifts and host masses.

No single model reliably reproduces the satellite luminosity function across all conditions.

Highlights the need for improved understanding of satellite galaxy evolution physics.

Abstract

It is widely believed that the large discrepancy between the observed number of satellite galaxies and the predicted number of dark subhalos can be resolved via a variety of baryonic effects which suppress star formation in low mass halos.Supporting this hypothesis, numerous high resolution simulations with star formation, and associated feedback have been shown to reproduce the satellite luminosity function around Milky Way-mass simulated galaxies at redshift zero. However, a more stringent test of these models is their ability to simultaneously match the satellite luminosity functions of a range of host halo masses and redshifts. In this work we measure the luminosity function of faint (sub-Small Magellanic Cloud luminosity) satellites around hosts with stellar masses 10.5$<\log_{10}$M$_*$/M$_\odot<11.5$ to an unprecedented redshift of 1.5. This new measurement of the satellite luminosity function provides powerful new constraining power; we compare these results with predictions from four different simulations and show that although the models perform similarly over-all, no one model reproduces the satellite luminosity function reliably at all redshifts and host stellar masses. This result highlights the continued need for improvement in understanding the fundamental physics that governs satellite galaxy evolution.