Near-UV Merger Signatures in Early-Type Galaxies

TL;DR

This study uses near-ultraviolet imaging from HST to detect signs of mixed stellar populations in the cores of early-type galaxies, revealing that most have composite populations indicative of hierarchical assembly.

Contribution

It provides observational evidence of composite stellar populations in early-type galaxy cores using high-resolution near-UV imaging, highlighting the prevalence of merger signatures.

Findings

10 out of 12 galaxies show evidence of composite populations.

Only 2 galaxies have colors consistent with a single-generation population.

Near-UV imaging effectively detects younger stellar components in galaxy cores.

Abstract

Hierarchical assembly of early-type galaxies (Es and S0s) over an extended period of time will result in mixed-generation stellar populations. Here we look for signatures of composite populations in broad-band, near-ultraviolet (2500-3400 A), high-resolution HST imaging of the cores of 12 bright early-type galaxies without obvious dust or active galactic nuclei. Near-UV imaging is a sensitive probe for the detection of younger components with ages in the range of 10 Myr to 5 Gyr. Only two galaxies have central colors (r < 0.75 r_eff) that are consistent with a single-generation population. The other ten require a composite population.