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

Abstract

Context. The very center (r ≪ r_e) of NGC 3610, a clearly disturbed giant elliptical that is generally assumed to be a post-merger remnant, appears dominated in the mid-UV (2500-3200 Å spectral region) by a stellar population that is markedly different from that dominating the bulk of its stellar body.
Aims: We make use of the mid-UV spectra of NGC 3610 as seen through tiny (~1'') and large (10'' × 20'') apertures as a diagnostic population tool.
Methods: We compare archive IUE/LWP large aperture and HST/FOS UV data of NGC 3610.
Results: 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 ~0.5 r_e (IUE).
Conclusions: The sub-arsec (mid)-UV properties of this galaxy involved in a past merger reveal a central metal enrichment which left the bulk of its pre-existing population intact.