THE zCOSMOS 20k GROUP CATALOG

Journal Article · Tue Jul 10 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/753/2/121· OSTI ID:22039396

Knobel, C; Lilly, S J; Kovac, K; Bschorr, T J; Oesch, P A; Kampczyk, P; Carollo, C M; Caputi, K ^[1]; Iovino, A; Presotto, V ^[2]; Contini, T ^[3]; Kneib, J -P; Le Fevre, O ^[4]; Mainieri, V ^[5]; Renzini, A ^[6]; Scodeggio, M ^[7]; Zamorani, G; Bardelli, S; Bolzonella, M ^[8]; Bongiorno, A ^[9] ; others, and

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1. Institute for Astronomy, ETH Zurich, Zurich 8093 (Switzerland)
2. INAF Osservatorio Astronomico di Brera, Milan (Italy)
3. Institut de Recherche en Astrophysique et Planetologie, CNRS, 14 Avenue Edouard Belin, F-31400 Toulouse (France)
4. Laboratoire d'Astrophysique de Marseille, CNRS/Aix-Marseille Universite, 38 rue Frederic Joliot-Curie, 13388 Marseille Cedex 13 (France)
5. European Southern Observatory, Garching (Germany)
6. INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova (Italy)
7. INAF-IASF Milano, Milano (Italy)
8. INAF Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)
9. Max Planck Institut fuer Extraterrestrische Physik, Garching (Germany)

We present an optical group catalog between 0.1 {approx}< z {approx}< 1 based on 16,500 high-quality spectroscopic redshifts in the completed zCOSMOS-bright survey. The catalog published herein contains 1498 groups in total and 192 groups with more than five observed members. The catalog includes both group properties and the identification of the member galaxies. Based on mock catalogs, the completeness and purity of groups with three and more members should be both about 83% with respect to all groups that should have been detectable within the survey, and more than 75% of the groups should exhibit a one-to-one correspondence to the 'real' groups. Particularly at high redshift, there are apparently more galaxies in groups in the COSMOS field than expected from mock catalogs. We detect clear evidence for the growth of cosmic structure over the last seven billion years in the sense that the fraction of galaxies that are found in groups (in volume-limited samples) increases significantly with cosmic time. In the second part of the paper, we develop a method for associating galaxies that only have photo-z to our spectroscopically identified groups. We show that this leads to improved definition of group centers, improved identification of the most massive galaxies in the groups, and improved identification of central and satellite galaxies, where we define the former to be galaxies at the minimum of the gravitational potential wells. Subsamples of centrals and satellites in the groups can be defined with purities up to 80%, while a straight binary classification of all group and non-group galaxies into centrals and satellites achieves purities of 85% and 75%, respectively, for the spectroscopic sample.

• OSTI ID: 22039396
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 753; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
CATALOGS
CLASSIFICATION
COSMOLOGY
DATA ANALYSIS
GALAXIES
RED SHIFT
SATELLITES
UNIVERSE