Ultracompact dwarf candidates in the Hydra cluster

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 ultracompact dwarfs ( UCDs). We identify 29 UCD candidates with estimated masses >6 x 10(6) M circle dot 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.