• DOI:10.1088/0004-637X/765/2/109
• Corpus ID: 17700696

PROTO-GROUPS AT 1.8 < z < 3 IN THE zCOSMOS-DEEP SAMPLE

@article{Diener2013PROTOGROUPSA1,
  title={PROTO-GROUPS AT 1.8 < z < 3 IN THE zCOSMOS-DEEP SAMPLE},
  author={Catrina Diener and Simon J. Lilly and Christian Knobel and Giovanni Zamorani and Gerard Lemson and P. Kampczyk and Nicholas Z. Scoville and C. Marcella Carollo and Thierry Contini and Jean-Paul Kneib and Olivier Le F{\`e}vre and Vincenzo Mainieri and Alvio Renzini and Marco Scodeggio and Sandro Bardelli and Micol Bolzonella and Angelo Bongiorno and Karina I. Caputi and Olga Cucciati and Sylvain de la Torre and Loic de Ravel and Paolo Franzetti and Bianca Garilli and Angela Iovino and K. Kovavc and Fabrice Lamareille and J. F. Le Borgne and Vincent Le Brun and Christian Maier and Marco Mignoli and Roser Pell{\'o} and Y. Peng and Enrique P{\'e}rez Montero and Valentina Presotto and John D. Silverman and M. Tanaka and Lidia A. M. Tasca and Laurence Tresse and D. Vergani and Elena Zucca and Rongmon Bordoloi and Alberto Cappi and Andrea Cimatti and Graziano Coppa and Anton M. Koekemoer and Carlos L'opez-Sanjuan and Henry Joy McCracken and M. Moresco and Preethi Nair and Lucia Pozzetti and Niraj Welikala},
  journal={The Astrophysical Journal},
  year={2013},
  volume={765}
}

• C. Diener, S. Lilly, +48 authors N. Welikala
• Published 9 October 2012
• Physics
• The Astrophysical Journal

We identify 42 “candidate groups” lying between 1.8 < z < 3.0 from a sample of 3502 galaxies with spectroscopic redshifts in the zCOSMOS-deep redshift survey within this same redshift interval. These systems contain three to five spectroscopic galaxies that lie within 500 kpc in projected distance (in physical space) and within 700 km s−1 in velocity. Based on extensive analysis of mock catalogs that have been generated from the Millennium simulation, we examine the likely nature of these systems at the time of observation, and what they will evolve into down to the present epoch. Although few of the “member” galaxies are likely to reside in the same halo at the epoch we observe them, 50% of the systems will have, by the present epoch, all of the member galaxies in the same halo, and almost all (93%) will have at least some of the potential members in the same halo. Most of the candidate groups can therefore be described as “proto-groups.” A crude estimate of the overdensities of these structures is also consistent with the idea that these systems are being seen as they assemble. We also examine present-day halos and ask whether their progenitors would have been seen among our candidate groups. For present-day halos between 1014 and 1015 M☉ h−1, 35% should have appeared among our candidate groups, and this would have risen to 70% if our survey had been fully sampled, so we can conclude that our sample can be taken as representative of a large fraction of such systems. There is a clear excess of massive galaxies above 1010 M☉ around the locations of the candidate groups in a large independent COSMOS photo-z sample, but we see no evidence in this latter data for any color differentiation with respect to the field. This is, however, consistent with the idea that such differentiation arises in satellite galaxies, as indicated at z < 1, if the candidate groups are indeed only starting to be assembled.