Discovery of a galaxy cluster with a violently starbursting core at z=2.506

Sargent, Mark (2016) Discovery of a galaxy cluster with a violently starbursting core at z=2.506. Astrophysical Journal, 828 (1). p. 56. ISSN 0004-637X

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We report the discovery of a remarkable concentration of massive galaxies with extended X-ray emission at zspec=2.506, which contains 11 massive (M∗≳1011M⊙) galaxies in the central 80-kpc region (11.6σ overdensity). We have spectroscopically confirmed 17 member galaxies with 11 from CO and the remaining ones from Hα. The X-ray luminosity, stellar mass content and velocity dispersion all point to a collapsed, cluster-sized dark matter halo with mass M200c=1013.9±0.2M⊙, making it the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this structure is dominated by star-forming galaxies (SFGs) in the core with only two out of the 11 massive galaxies classified as quiescent. The star formation rate (SFR) in the 80-kpc core reaches ∼3400 M⊙ yr−1 with gas depletion time of ∼200 Myr, suggesting that we caught this cluster in rapid build-up of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst fraction (∼25%, compared to 3\%-5\% in the field). The presence of both a collapsed, cluster-sized halo and a predominant population of massive SFGs suggests that this structure could represent an important transition phase between protoclusters and mature clusters. It provides evidence that the main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster, providing new insights into massive cluster formation at early epochs. The large integrated stellar mass at such high redshift challenges our understanding of massive cluster formation.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QB Astronomy
Depositing User: Mark Sargent
Date Deposited: 08 Aug 2016 09:12
Last Modified: 11 Sep 2017 19:42

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