UCD Candidates in the Hydra Cluster

Abstract

NGC 3311, the giant cD galaxy in the Hydra cluster (A1060), has one of the largest globular cluster systems known. We describe new Gemini GMOS (g',i') photometry of the NGC 3311 field which reveals that the red, metal-rich side of its globular cluster population extends smoothly upward into the mass range associated with the new class of Ultra-Compact Dwarfs (UCDs). We identify 29 UCD candidates with estimated masses > 6x10^6 solar masses and discuss their characteristics. This UCD-like sequence is the most well defined one yet seen, and reinforces current ideas that the high-mass end of the globular cluster sequence merges continuously into the UCD sequence, which connects in turn to the E galaxy structural sequence.

5 pages, 3 figures. Accepted for publication in ApJ Letters

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• Structural Properties of Ultra-Compact Dwarf Galaxies in the Fornax and Virgo Clusters
• The early-type dwarf galaxy population of the Hydra I cluster
• The Globular Cluster Systems in the Coma Ellipticals. IV: WFPC2 Photometry for Five Giant Ellipticals
• The Globular Cluster Systems around NGC 3311 and NGC 3309
• The photometric evolution of star clusters and the preferential loss of low-mass bodies - with an application to globular clusters
• Ultra-Compact Dwarf Candidates Near the Lensing Galaxy in Abell S0740
• A Glimpse into the Past: The Recent Evolution of Globular Clusters