Comparison of the Stellar Populations of Bulges and Discs using the MaNGA Survey

TL;DR

This study uses MaNGA survey data to compare stellar populations in bulges and discs of galaxies, revealing differences in metallicity and age related to galaxy mass, type, and environment, and suggesting inside-out quenching in high-mass galaxies.

Contribution

It provides a detailed comparison of bulge and disc stellar populations across galaxy types and masses using integral-field spectroscopy, highlighting environmental and evolutionary effects.

Findings

Bulges are more metal-rich and slightly older than discs.

High-mass galaxies show greater metallicity and age differences.

Central galaxies exhibit larger metallicity contrasts than satellites.

Abstract

We use the MaNGA integral-field spectroscopic survey of low-redshift galaxies to compare the stellar populations of the bulge and disc components, identified from their Sersic profiles, for various samples of galaxies. Bulge dominated regions tend to be more metal-rich and have slightly older stellar ages than their associated disc dominated regions. The metallicity difference is consistent with the deeper gravitational potential in bulges relative to discs, which allows bulges to retain more of the metals produced by stars. The age difference is due to star formation persisting longer in discs relative to bulges. Relative to galaxies with lower stellar masses, galaxies with higher stellar masses tend to have bulge dominated regions that are more metal-rich and older (in light-weighted measurements) than their disc dominated regions. This suggests high-mass galaxies quench from the inside out, while lower-mass galaxies quench across the whole galaxy simultaneously. Early-type galaxies tend to have bulge dominated regions the same age as their disc dominated regions, while late-type galaxies tend to have disc dominated regions significantly younger than their bulge dominated regions. Central galaxies tend to have a greater metallicity difference between their bulge dominated regions and disc dominated regions than satellite galaxies at similar stellar mass. This difference may be explained by central galaxies being subject to mergers or extended gas accretion bringing new, lower-metallicity gas to the disc, thereby reducing the average metallicity and age of the stars; quenching of satellite discs may also play a role.