SDSS-IV MaNGA: How the stellar populations of passive central galaxies depend on stellar and halo mass

Grecco A. Oyarzun, Kevin Bundy, Kyle B. Westfall, Jeremy L. Tinker, Francesco Belfiore, Maria Argudo-Fernandez, Zheng Zheng, Charlie Conroy, Karen L. Masters, David Wake, David R. Law, Richard M. McDermid, Alfonso Aragon-Salamanca, Taniya Parikh, Renbin Yan, Matthew Bershady, Sebastian F. Sanchez, Brett H. Andrews, Jose G. Fernandez-Trincado, Richard R. Lane, D. Bizyaev, Nicholas Fraser Boardman, Ivan Lacerna, J. R. Brownstein, Niv Drory, Kai Zhang

Published 2022-05-25Version 1

We analyze spatially resolved and co-added SDSS-IV MaNGA spectra with signal-to-noise ~100 from 2200 passive central galaxies (z~0.05) to understand how central galaxy assembly depends on stellar mass (M*) and halo mass (Mh). We control for systematic errors in Mh by employing a new group catalog from Tinker (2020a,b) and the widely-used Yang et al. (2007) catalog. At fixed M*, the strength of several stellar absorption features varies systematically with Mh. Completely model-free, this is one of the first indications that the stellar populations of centrals with identical M* are affected by the properties of their host halos. To interpret these variations, we applied full spectral fitting with the code alf. At fixed M*, centrals in more massive halos are older, show lower [Fe/H], and have higher [Mg/Fe] with 3.5 sigma confidence. We conclude that halos not only dictate how much M* galaxies assemble, but also modulate their chemical enrichment histories. Turning to our analysis at fixed Mh, high-M* centrals are older, show lower [Fe/H], and have higher [Mg/Fe] for Mh>10^{12}Msun/h with confidence > 4 sigma. While massive passive galaxies are thought to form early and rapidly, our results are among the first to distinguish these trends at fixed Mh. They suggest that high-M* centrals experienced unique early formation histories, either through enhanced collapse and gas fueling, or because their halos were early-forming and highly concentrated, a possible signal of galaxy assembly bias.