The merger remnant NGC 3610 and its globular cluster system: a large-scale study

Abstract

We present a photometric study of the prototype merger remnant NGC 3610and its globular cluster (GC) system, based on new GEMINI/GMOS andACS/HST archival images. Thanks to the large FOV of our GMOS data,larger than previous studies, we are able to detect a `classical´bimodal GC colour distribution, correponding metal-poor and metal-richGCs, at intermediate radii and a small subsample of likely youngclusters of intermediate colours, mainly located in the outskirts. Theextent of the whole GC system is settled as about 40 kpc. The GCpopulation is quite poor, about 500 ± 110 members thatcorresponds to a low total specific frequency S_N ? 0.8.The effective radii of a cluster sample are determined, including thoseof two spectroscopically confirmed young and metal-rich clusters, thatare in the limit between GC and UCD sizes and brightness. Thelarge-scale galaxy surface-brightness profile can be decomposed as aninner embedded disc and an outer spheroid, determining for both largerextents than earlier research (10 kpc and 30 kpc, respectively). Wedetect boxy isophotes, expected in merger remnants, and show a wealth offine-structure in the surface-brightness distribution with unprecedenteddetail, coincident with the outer spheroid. The lack of symmetry in thegalaxy colour map adds a new piece of evidence to the recent mergerscenario of NGC 3610.