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Massive starburst galaxies in a z = 2.16 proto-cluster unveiled by panoramic Hα mapping.

Koyama, Y. and Kodama, T. and Tadaki, K.-i. and Hayashi, M. and Tanaka, M. and Smail, I. and Tanaka, I. and Kurk, J. (2013) 'Massive starburst galaxies in a z = 2.16 proto-cluster unveiled by panoramic Hα mapping.', Monthly notices of the Royal Astronomical Society., 428 (2). pp. 1551-1564.


We present a panoramic narrow-band study of Hα emitters in the field of the z = 2.16 proto-cluster around PKS 1138−262 using MOIRCS on the Subaru Telescope. We find 83 Hα emitters down to a star formation rate of SFR (Hα) ∼ 10 M⊙ yr−1 across a ∼ 7 × 7 arcmin2 region centred on the radio galaxy, and identify ∼10-Mpc scale filaments of emitters running across this region. By examining the properties of Hα emitters within the large-scale structure, we find that galaxies in the higher density environments at z = 2.16 tend to have redder colours and higher stellar masses compared to galaxies in more underdense regions. We also find a population of Hα emitters with red colours [(J − Ks) ≳ 1], which are much more frequent in the denser environments and which have apparently very high stellar masses with M* ≳ 1011 M⊙, implying that these cluster galaxies have already formed a large part of their stellar mass before z ∼ 2. Spitzer Space Telescope 24-μm data suggest that many of these red Hα emitters are bright, dusty starbursts (rather than quiescent sources). We also find that the proto-cluster galaxies follow the same correlation between SFR and M* (the ‘main sequence’) of z ∼ 2 field star-forming galaxies, but with an excess of massive galaxies. These very massive star-forming galaxies are not seen in our similar, previous study of z ∼ 1 clusters, suggesting that their star formation activity has been shut off at 1 ≲ z ≲ 2. We infer that the massive red (but active) galaxies in this rich proto-cluster are likely to be the products of environmental effects, and they represent the accelerated galaxy formation and evolution in a biased high-density region in the early Universe.

Item Type:Article
Keywords:Galaxies: clusters: individual: PKS 1138−262, Galaxies: evolution, Large-scale structure of Universe
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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2013 The Authors Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.
Date accepted:No date available
Date deposited:19 June 2014
Date of first online publication:January 2013
Date first made open access:No date available

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