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

TL;DR

This study uses spatially resolved spectra from SDSS-IV MaNGA to show that the stellar populations of passive central galaxies are influenced by both stellar and halo mass, revealing new insights into galaxy assembly and chemical enrichment histories.

Contribution

It demonstrates that halo properties affect stellar populations of galaxies with the same stellar mass, providing new evidence for halo influence on galaxy evolution.

Findings

Centrals in more massive halos are older, with lower [Fe/H] and higher [Mg/Fe].

At fixed M*, higher halo mass correlates with older age and different chemical abundances.

High-M* centrals in massive halos show signs of early, rapid formation histories.

Abstract

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.