Two formation channels of UCDs in Hickson Compact Groups

Details Two formation channels of UCDs in Hickson Compact Groups Two formation channels of UCDs in Hickson Compact Groups

2010-09-15

arxiv.org/abs/1009.3010v1

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

Accepted for publication at A&A, 17 pages, 9 figures + 2 additional figures

Scientific paper

The formation of ultra-compact dwarf galaxies (UCDs) is believed to be interaction driven, and UCDs are abundant in the cores of galaxy clusters, environments that mark the end-point of galaxy evolution. Nothing is known about the properties of UCDs in compact groups of galaxies, environments where most of galaxy evolution and interaction is believed to occur and where UCDs in intermediate state of evolution may be expected. The main goal of this study is to detect and characterize, for the first time, the UCD population of compact groups. For that, 2 groups in different evolutionary stages, HCG 22 and HCG 90, were targeted with VLT/FORS2/MXU. We detect 16 and 5 objects belonging to HCG 22 and HCG 90, respectively, covering the magnitude range -10.0 > M_R > -11.5 mag. Their colours are consistent with old ages covering a broad range in metallicities. Photometric mass estimates put 4 objects in HCG 90 and 9 in HCG 22 in the mass range of UCDs (>2x10^6 M_Sun) for an assumed age of 12 Gyr. These UCDs are on average 2-3 times larger than typical Galactic GCs, covering a range of 2 >~ r_h >~ 21 pc. The UCDs in HCG 22 are more concentrated around the central galaxy than in HCG 90, at the 99% confidence level. They cover a broad range in [alpha/Fe] abundances from sub- to super-solar. The spectra of 3 UCDs show tentative evidence for intermediate age stellar populations. We calculate the specific frequency (S_N) of UCDs for both groups, finding that HCG 22 has about three times higher S_N than HCG 90. The ensemble properties of the detected UCDs supports 2 co-existing formation channels: a star cluster origin and an origin as tidally stripped dwarf nuclei. Our results imply that the UCDs detected in both groups do not, in their majority, originate from relatively recent galaxy interactions. Most of the detected UCDs have likely been brought into the group with their host galaxies.[abridged]

Affiliated with

Also associated with

No associations

Rating

Two formation channels of UCDs in Hickson Compact Groups does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Two formation channels of UCDs in Hickson Compact Groups, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Two formation channels of UCDs in Hickson Compact Groups will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-26292