Ultra-Compact Dwarfs around NGC 3268

TL;DR

This study identifies and analyzes 35 ultra-compact dwarfs and bright globular clusters around NGC 3268 in the Antlia cluster, measuring their properties and estimating the galaxy's mass.

Contribution

It provides the first comprehensive radial velocity and size measurements of UCDs in Antlia, supporting their classification as bright globular clusters and estimating the galaxy's mass.

Findings

35 UCDs and bright GCs identified around NGC 3268

UCDs have effective radii up to ~10 pc

Mass enclosed within 47 kpc is approximately 2.7 x 10^12 solar masses

Abstract

We present radial velocities (from Gemini/GMOS) of the second sample of ultra-compact dwarfs (UCDs) and bright globular clusters (GCs) in the Antlia cluster. Twenty-three objects are located around the giant elliptical NGC 3268, and one is close to the fainter lenticular NGC 3273. Together with previously found UCDs around NGC 3258 a total of 35 UCDs and bright GCs has been now identified in the Antlia cluster. Their colours and magnitudes are compared with those of the nuclei of dE,N galaxies already confirmed as Antlia members. For a subsample that lie on ACS images and are brighter than M_V = -9 mag, the effective radii (R_eff) have been measured, the maximum radius being approximately 10 pc. In addition to the radial velocity sample, we find 10 objects in the magnitude range corresponding to GCs but with 10 < R_eff < 17 pc, resembling the so-called `extended clusters'. By number and magnitude, the new UCDs fit to the GC luminosity function, supporting their interpretation as bright GCs. Additionally, we use a tracer mass estimator to calculate the mass enclosed up to ~47 kpc from NGC 3268, which results in 2.7 x 10^12 M_o.