Selection criteria: 21 < R < 24 (-14 < M R < -11) 0.45 < (B – V) < 1.1 (3 arcsec apertures) Highest priority to sources showing any sign of having profiles broader than stellar in ACS images Unresolved in ground-based images (CFHT/CFH12K Adami et al. 2006) Higher priority to sources with 0.15 < R – I < 0.6 Located in the core region with processed ACS images available before Feb. 11, UCDs in the Coma Cluster Known properties: < M V < < R e < 100 pc (V-I) = Fornax – red, Virgo - blue Kristin Chiboucas – Liverpool Coma Cluster Treasury Team Meeting – 16 April 2009

Targetted 47 candidates in 4 masks : Measured secure redshifts for 29, including 4 background objects 6 stars Z = R = 23.4 M R = Z = R = 21.7 M R = Z = R = 22.1 M R = -12.9

17.5˝

19 confirmed UCDs (4000 < cz < 10,000 km/s) 6 questionable UCDs 6 stars 4 background galaxies 12 failed (S/N too low) 47 targets 18 / 27 (with R < 23.3) cluster members 66% are members!

Properties of our confirmed UCDs

UCD Colors

Velocity distribution = 7207 ± 144 km/s = 6299 ± 242 = 6968 ± 316 km/s = 6473 ± 207 = 6968 ± 172, σ v = 1218 = 6681 ± 183, σ v = 797

7 UCDs near NGC 4874: = 7313 ± 114 km/s σ v = 300 km/s Maximum projected distance 3.7 arcmin (108 kpc) Consistent with being bound to NGC 4874.

Globular Cluster color distribution F814W > 24.7 F814W < 24.7 GC (g – I) 0 Peaks: Blue: 0.94 Red: 1.19 UCD: Blue ave = 0.95 Red ave = 1.17

Physical Sizes (Sersic profile fitting) (King profile fitting)

Goal 2 nd LRIS run (27-29 March): To fully characterize the properties and spatial distribution of the UCD population. 3 masks, ~ objects per mask Lousy weather: 1st 2 nights thick cirrus, 3rd night thin cirrus + poor seeing Targetted mask centered on IC 4051 first 2 nights, and central mask the 3rd night

New candidate selection based on confirmed UCDs

What we’ve learned so far: Large population of UCDs in the rich, dynamically evolved Coma cluster UCDs appear to reside preferentially in core region or associated with giant galaxies in the core and have a lower population velocity dispersion than other galaxy types. Properties are consistent with what has been found in other clusters. Properties and spatial distribution consistent with UCDs as bright extension of GC sequence However, that would not explain the high M/L ratios found for UCDs in other clusters. We also see some similarities with cEs. Still to do: Line index stellar population ages, metallicities Comparison with properties of nuclei of dE,Ns

Ultra Compact Dwarfs in the Coma Cluster  Kristin Chiboucas  Brent Tully  Ron Marzke  Steve Phillipps  James Price  Eric Peng  …