The mid-UV population of the nucleus and the bulk of the post-merger NGC 3610

TL;DR

This study uses mid-UV spectral data from HST and IUE to analyze the stellar populations in NGC 3610, revealing a central metal enrichment and differences between core and outer regions post-merger.

Contribution

It provides new insights into the stellar population distribution in NGC 3610 using UV spectral diagnostics from different aperture sizes.

Findings

Central region shows metal enrichment post-merger.

Mid-UV triplet strength drops from core to outer regions.

Outer regions retain pre-merger stellar populations.

Abstract

The very center of NGC~3610, a clearly disturbed giant elliptical generally assumed to be a post-merger remnant, appears dominated in the mid-UV (2500-3200 A spectral region) by a stellar population markedly different from that dominating the bulk of its stellar body. I want here to make use of the mid-UV spectra of NGC~3610 as seen through tiny ($\sim$1") and large (10"$\times$20") apertures as a diagnostic population tool. I compare archive IUE/LWP large aperture and HST/FOS UV data of NGC 3610. The strength of mid-UV triplet (dominated by the turnoff population) shows a remarkable drop when switching from the galaxy central arcsec (FOS aperture) to an aperture size comparable to $\sim$0.5 r$_e$ (IUE). The sub-arsec (mid)-UV properties of this galaxy involved in a past merger reveal a central metal enrichment which left intact the bulk of its pre-existing population.