Mapping the Stellar Mass Content of Central Galaxies in Dark Matter Halos*

The central galaxies in galaxy groups and clusters rank among the most massive galaxies in the universe, but a significant fraction of their stellar mass lies in the low surface-brightness and hard-to-detect outer envelope.  We use new deep optical and mid-infrared imaging of a sample of more than 20,000 central galaxies obtained as part of the DESI Legacy Imaging Surveys (http://legacysurvey.org) to measure their azimuthally averaged stellar mass profiles and integrated stellar masses using state-of-the-art photometric and stellar population synthesis modeling techniques.  We present new measurements of the stellar mass function and stellar mass-halo mass relation for central galaxies, and discuss the implications of our results for numerical simulations of star formation and feedback in massive galaxies.