Deciphering the activity and quiescence of high-redshift cluster environments: ALMA observations of Cl J1449+0856 at z = 2

Strazzullo, V, Coogan, R T, Daddi, E, Sargent, M T, Gobat, R, Valentino, F, Berthermin, M, Pannella, M, Dickinson, M, Renzini, A, Arimoto, N, Cimatti, A, Dannerbauer, H, Finoguenov, A, Liu, D and Onodera, M (2018) Deciphering the activity and quiescence of high-redshift cluster environments: ALMA observations of Cl J1449+0856 at z = 2. The Astrophysical Journal, 862 (64). pp. 1-11. ISSN 0004-637X

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We present ALMA observations of the 870μm continuum and CO(4-3) line emission in the core of the galaxy cluster ClJ1449+0856 at z=2, a NIR-selected, X-ray detected system in the mass range of typical progenitors of today's massive clusters. The 870μm map reveals six F870μm > 0.5 mJy sources spread over an area of 0.07 arcmin2, giving an overdensity of a factor ~10 (6) with respect to blank field counts down to F870μm > 1 (0.5) mJy. On the other hand, deep CO(4-3) follow-up confirms membership of three of these sources, but suggests that the remaining three, including the brightest 870μm sources in the field (F870μm≳2 mJy), are likely interlopers. The measurement of 870μm continuum and CO(4-3) line fluxes at the positions of previously-known cluster members provides a deep probe of dusty star formation occurring in the core of this high-redshift structure, adding up to a total SFR~700±100 M⊙/yr and yielding an integrated star formation rate density of ~104 M⊙/yr/Mpc3, five orders of magnitude larger than in the field at the same epoch, due to the concentration of star-forming galaxies in the small volume of the dense cluster core. The combination of these observations with previously available HST imaging highlights the presence in this same volume of a population of galaxies with already suppressed star formation. This diverse composition of galaxy populations in ClJ1449+0856 is especially highlighted at the very cluster center, where a complex assembly of quiescent and star-forming sources is likely forming the future Brightest Cluster Galaxy.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Research Centres and Groups: Astronomy Centre
Subjects: Q Science > QB Astronomy
Depositing User: Mark Sargent
Date Deposited: 23 Aug 2018 12:54
Last Modified: 23 Aug 2018 13:07

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