http://arxiv.org/abs/1402.3568
We present the results of near-infrared spectroscopy of H-alpha emitters (HAEs) associated with two proto-clusters around radio galaxies (PKS1138-262 at z=2.2 and USS1558-003 at z=2.5) with MOIRCS on Subaru telescope. Among the HAE candidates constructed from our narrow-band imaging, we have confirmed membership of 27 and 36 HAEs for the respective proto-clusters, with a success rate of 70% of our observed targets. The large number of spectroscopically confirmed members per cluster has enabled us for the first time to reveal the detailed kinematical structures of the proto-clusters at z>2. The clusters show prominent substructures such as clumps, filaments and velocity gradient, suggesting that they are still in the midst of rapid construction to grow to rich clusters at later times. We also estimate dynamical masses of the clusters and substructures assuming their local virialization. The inferred masses (~10e+14 Msun) of the proto-cluster cores are consistent with being typical progenitors of the present-day most massive class of galaxy clusters (~10e+15 Msun) if we take into account the typical mass growth history of clusters. We then calculated the integrated star formation rates of the proto-cluster cores normalized by the dynamical masses, and compare those with lower redshift descendants. We see a marked increase of star-forming activities in the cluster cores by almost three orders of magnitude as we go back in time to 11 billion years ago and it scales as (1+z)^6.
R. Shimakawa, T. Kodama, K. Tadaki, et. al.
Mon, 17 Feb 14
16/37
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