B. C. Lemaux, Aix-Marseille Université, France
O. Cucciati, University of Bologna, Italy
L. A. M. Tasca, Aix-Marseille Université, France
O. Le Fèvre, Aix-Marseille Université, France
G. Zamorani, INAF – Osservatorio Astronomico di Bologna, Italy
P. Cassata, Aix-Marseille Université, France
B. Garilli, INAF – IASF, Italy
V. Le Brun, Aix-Marseille Université, France
D. Maccagni, INAF – IASF, Italy
L. Pentericci, INAF – Osservatorio Astronomico di Roma, Italy
R. Thomas, Aix-Marseille Université, France
E. Vanzella, INAF−Osservatorio Astronomico di Bologna, Italy
R. Amorín, INAF – Osservatorio Astronomico di Roma, Italy
S. Bardelli, INAF−Osservatorio Astronomico di Bologna, Italy
P. Capak, California Institute of Technology
L. P. Cassarà, INAF – IASF, Italy
M. Castellano, INAF – Osservatorio Astronomico di Roma, Italy
A. Cimatti, University of Bologna, Italy
J. G. Cuby, Aix-Marseille Université, France
S. de la Torre, Aix-Marseille Université, France
A. Durkalec, Aix-Marseille Université, France
A. Fontana, INAF – Osservatorio Astronomico di Roma, Italy
M. Giavalisco, University of Massachusetts - Amherst
A. Grazian, INAF – Osservatorio Astronomico di Roma, Italy
N. P. Hathi, Aix-Marseille Université, France
O. Ilbert, Aix-Marseille Université, France
C. Moreau, Aix-Marseille Université, France
S. Paltani, University of Geneva, Switzerland
B. Ribeiro, Aix-Marseille Université, France
M. Salvato, Max-Planck-Institut für extraterrestrische Physik, Germany
D. Schaerer, University of Geneva, Switzerland
M. Scodeggio, INAF – IASF, Italy
V. Sommariva, University of Bologna, Italy
M. Talia, University of Bologna, Italy
Y. Taniguchi, Ehime University, Japan
L. Tresse, Aix-Marseille Université, France
D. Vergani, INAF – IASF Bologna, Italy
P. W. Wang, Aix-Marseille Université, France
S. Charlot, Université Pierre et Marie Curie, France
T. Contini, Université de Toulouse, France
S. Fotopoulou, University of Geneva, Switzerland
R. R. Gal, University of Hawai’i
Dale D. Kocevski, University of KentuckyFollow
C. López-Sanjuan, Centro de Estudios de Física del Cosmos de Aragón, Spain
L. M. Lubin, University of California - Davis
Y. Mellier, Université Pierre et Marie Curie, France
T. Sadibekova, CEA-Saclay, France
N. Scoville, California Institute of Technology


Using new spectroscopic observations obtained as part of the VIMOS Ultra-Deep Survey (VUDS), we performed a systematic search for overdense environments in the early universe (z> 2) and report here on the discovery of Cl J0227-0421, a massive protocluster at z = 3.29. This protocluster is characterized by both the large overdensity of spectroscopically confirmed members, δgal = 10.5 ± 2.8, and a significant overdensity in photometric redshift members. The halo mass of this protocluster is estimated by a variety of methods to be ~3 × 1014 at z ~ 3.3, which, evolved to z = 0 results in a halo mass rivaling or exceeding that of the Coma cluster. The properties of 19 spectroscopically confirmed member galaxies are compared with a large sample of VUDS/VVDS galaxies in lower density field environments at similar redshifts. We find tentative evidence for an excess of redder, brighter, and more massive galaxies within the confines of the protocluster relative to the field population, which suggests that we may be observing the beginning ofenvironmentally induced quenching. The properties of these galaxies are investigated, including a discussion of the brightest protocluster galaxy, which appears to be undergoing vigorous coeval nuclear and starburst activity. The remaining member galaxies appear to have characteristics that are largely similar to the field population. Though we find weaker evidence of the suppression of the median star formation rates among and differences in the stacked spectra of member galaxies with respect to the field, we defer any conclusions about these trends to future work with the ensemble of protostructures that are found in the full VUDS sample.

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Notes/Citation Information

Published in Astronomy & Astrophysics, v. 572, article A41, p. 1-23.

© ESO, 2014

The copyright holders have granted the permission for posting the article here.

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Funding Information

This work is supported by funding from the European Research Council Advanced Grant ERC- 2010-AdG-268107-EARLY and by INAF Grants PRIN 2010, PRIN 2012 and PICS 2013. A.C., O.C., M.T. and V.S. acknowledge the grant MIUR PRIN 2010– 2011.

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This work is based on data products made available at the CESAM data center, Laboratoire d’Astrophysique de Marseille. This work partly uses observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. A portion of the spectroscopic data presented herein were obtained at the W. M. Keck Observatory. We wish to thank the indigenous Hawaiian community for allowing us to be guests on their sacred mountain; we are most fortunate to be able to conduct observations from this site.