http://arxiv.org/abs/1403.0040
We present a deep Jansky Very Large Array observation of CO J=1-0 emission line in a proto-cluster at z=2.53, USS1558-003. The target field is an especially dense region, where 20 H-alpha emitters (HAEs) are clustering. We successfully detect CO emission lines from four HAEs and give an upper limit for 16 HAEs. Red, massive star-forming galaxies tend to be gas rich while blue less massive galaxies are faint in the CO emission. Given the close proximity (32 kpc), small velocity offset (130 km/s), and similar stellar masses of the two CO emitters, ID 191 and ID 193, they could be in the phase prior to a gas-rich major merger. ID 193 shows a red color in the rest-frame optical, suggesting the presence of dusty star-formation. Using MIPS 24 um and radio continuum images, we find a total infrared luminosity of L(IR)=5.1e12 Lsun for ID 193, corresponding to SFR~880 Msun/yr. The L(IR)/L'(CO) ratio is significantly enhanced compared to local spirals/high-redshift disks at a fixed CO luminosity, which is indicative of a starburst mode. Our results suggest that ID 193 lies in the late stage of merger where violent star formation is induced by a past interaction with a gas-rich galaxy but the neighboring blue HAE, ID 191. The most intriguing result is that such a system is discovered in an extremely dense region at z>2. The formation processes of slow rotators seen in local massive clusters may involve such multiple gas-rich mergers in proto-clusters at z>2.
K. Tadaki, T. Kodama, Y. Tamura, et. al.
Tue, 4 Mar 14
39/61
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