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 .