Ultra-Compact Dwarfs around NGC 3268

Abstract

We present radial velocities (from Gemini/GMOS) of the second sample of ultracompact dwarfs (UCDs) and bright globular clusters (GCs) in the Antlia cluster. 23 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 (Advanced Camera for Surveys) images and are brighter than MV = − 9 mag, the effective radii (Reff ) 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 < Reff < 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 approx. 47 kpc from NGC 3268, which results in 2.7 x 10^12 solar masses.