The Most Massive Ultra-compact Dwarf Galaxy in the Virgo Cluster
Abstract
We report on the properties of the most massive ultra-compact dwarf galaxy (UCD) in the nearby Virgo Cluster of galaxies using imaging from the Next Generation Virgo Cluster Survey and spectroscopy from Keck/DEIMOS. This object (M59-UCD3) appears to be associated with the massive Virgo galaxy M59 (NGC 4621), has an integrated velocity dispersion of 78 {km} {{{s}}}-1, a dynamical mass of 3.7× {10}8{M}⊙ , and an effective radius (Re) of 25 pc. With an effective surface mass density of 9.4× {10}10{M}⊙ {{kpc}}-2, it is the densest galaxy in the local universe discovered to date, surpassing the density of the luminous Virgo UCD, M60-UCD1. M59-UCD3 has a total luminosity of {M}{g\prime }=-14.2 mag, and a spectral energy distribution consistent with an old (14 Gyr) stellar population with [Fe/H] = 0.0 and [α /{Fe}]=+0.2. We also examine deep imaging around M59 and find a broad low surface brightness stream pointing toward M59-UCD3, which may represent a tidal remnant of the UCD progenitor. This UCD, along with similar objects like M60-UCD1 and M59cO, likely represents an extreme population of tidally stripped galaxies more akin to larger and more massive compact early-type galaxies than to nuclear star clusters in present-day dwarf galaxies.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2015
- DOI:
- 10.1088/2041-8205/812/1/L2
- arXiv:
- arXiv:1508.07373
- Bibcode:
- 2015ApJ...812L...2L
- Keywords:
-
- galaxies: clusters: individual: Virgo;
- galaxies: dwarf;
- galaxies: evolution;
- galaxies: individual: M59;
- galaxies: nuclei;
- galaxies: star clusters: general;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 6 pages, 4 figures, 1 table, accepted for publication in ApJ Letters