# Impact of Galaxy Mergers on Stellar Population Profiles of Early-type Galaxies

## TL;DR

This study investigates how galaxy mergers influence the stellar population gradients in early-type galaxies, revealing that recent mergers lead to less negative metallicity gradients and younger stellar ages, indicating ongoing star formation and chemical enrichment.

## Contribution

It provides observational evidence linking recent galaxy mergers to changes in stellar population profiles in early-type galaxies, highlighting differences in metallicity and age gradients.

## Key findings

- ETGs with tidal features have less negative metallicity gradients.
- ETGs with tidal features are younger by 1-2 Gyr.
- Recent mergers accelerate metal enrichment in ETGs.

## Abstract

We study the impact of galaxy mergers on stellar population profiles/gradients of early-type galaxies (ETGs) using ETGs at $z<0.055$ in the Stripe 82 region of the Sloan Digital Sky Survey and MaNGA integral field unit spectroscopic data. Tidal features around ETGs, which are detected from deep coadded images, are regarded as direct observational evidence for recent mergers. We find that ETGs with tidal features have less negative metallicity gradients and more positive age gradients than ETGs without tidal features at $M_\mathrm{star}\gtrsim10^{10.6}M_\odot$. Moreover, when integrating all the resolved stellar populations, ETGs with tidal features have lower metallicities by $\sim0.07$ dex and younger ages by $\sim1$ - $2$ Gyr than ETGs without tidal features. Analyzing star formation histories, we discover that the mass fraction of young stellar populations with age $<5$ Gyr is higher in the central regions of ETGs with tidal features than in the same regions of the counterparts without tidal features. Compared to normal ETGs, ETGs with tidal features have a slow metal-enrichment history in the early universe, but they have been accelerating the metal enrichment through recently formed stars over the last few billion years. Many of our results can be explained if the effects of recently occurred mergers are different from those in the early universe, which are more likely to be rich in gas.