A Gemini/GMOS study of the bright elliptical galaxy NGC 3613 and its globular cluster system

TL;DR

This study provides the first detailed photometric analysis of NGC 3613's globular cluster system and host galaxy, revealing bimodal color distribution, spatial differences, and a population estimate, contributing to understanding galaxy and cluster formation.

Contribution

First photometric study of NGC 3613's globular clusters and galaxy structure, including spatial distribution, population estimate, and identification of UCD candidates.

Findings

Bimodal color distribution of GCs with radial variation.

Metal-rich GCs are more concentrated and follow galaxy light.

Estimated total GC population is approximately 2075.

Abstract

We present the first photometric study of the globular cluster system (GCS) of the E galaxy NGC 3613 (Mv = -21.5, d = 30.1 Mpc), as well as the surface photometry of the host galaxy, based on Gemini/GMOS images. Being considered the central galaxy of a group, NGC 3613 inhabits a low-density environment although its intrinsic brightness is similar to the expected one for galaxies in the centre of clusters. The following characteristics are obtained for this GCS. The colour distribution is bimodal, with metal-poor globular clusters (GCs) getting slightly bluer with increasing radius. The radial and azimuthal projected distributions show that metal-rich GCs are more concentrated towards the host galaxy and trace its light distribution very precisely, while metal-poor GCs present a more extended and uniform distribution. The GC luminosity function helps validate the adopted distance. The estimated total GC population of Ntot= 2075 +/- 130 leads to a specific frequency Sn=5.2 +/- 0.7, a value within the expected range for GCSs with host galaxies of similar luminosity. The surface photometry of NGC 3613 reveals a three-component profile and a noticeable substructure. Finally, a small sample of ultra-compact dwarf (UCD) candidates are identified in the surroundings of the host galaxy.