An optical group catalogue to z = 1 from the zCOSMOS 10k sample
Abstract
We present a galaxy group catalogue spanning the redshift range 0.1 <~ z <~ 1 in the ~1.7 deg^2 COSMOS field, based on the first ~10,000 zCOSMOS spectra. The performance of both the Friends-of-Friends (FOF) and Voronoi-Delaunay-Method (VDM) approaches to group identification has been extensively explored and compared using realistic mock catalogues. We find that the performance improves substantially if groups are found by progressively optimizing the group-finding parameters for successively smaller groups, and that the highest fidelity catalogue, in terms of completeness and purity, is obtained by combining the independently created FOF and VDM catalogues. The final completeness and purity of this catalogue, both in terms of the groups and of individual members, compares favorably with recent results in the literature. The current group catalogue contains 102 groups with N >= 5 spectroscopically confirmed members, with a further ~700 groups with 2 <= N <= 4. Most of the groups can be assigned a velocity dispersion and a dark-matter mass derived from the mock catalogues, with quantifiable uncertainties. The fraction of zCOSMOS galaxies in groups is about 25% at low redshift and decreases toward ~15% at z ~ 0.8. The zCOSMOS group catalogue is broadly consistent with that expected from the semi-analytic evolution model underlying the mock catalogues. Not least, we show that the number density of groups with a given intrinsic richness increases from redshift z ~ 0.8 to the present, consistent with the hierarchical growth of structure.
Keywords
Cite
@article{arxiv.0903.3411,
title = {An optical group catalogue to z = 1 from the zCOSMOS 10k sample},
author = {C. Knobel and S. J. Lilly and A. Iovino and C. Porciani and K. Kovac and O. Cucciati and A. Finoguenov and M. G. Kitzbichler and C. M. Carollo and T. Contini and J. -P. Kneib and O. Le Fevre and V. Mainieri and A. Renzini and M. Scodeggio and G. Zamorani and S. Bardelli and M. Bolzonella and A. Bongiorno and K. Caputi and G. Coppa and S. de la Torre and L. de Ravel and P. Franzetti and B. Garilli and P. Kampczyk and F. Lamareille and J. -F. Le Borgne and V. Le Brun and C. Maier and M. Mignoli and R. Pello and Y. Peng and E. Perez Montero and E. Ricciardelli and J. D. Silverman and M. Tanaka and L. Tasca and L. Tresse and D. Vergani and E. Zucca and U. Abbas and D. Bottini and A. Cappi and P. Cassata and A. Cimatti and M. Fumana and L. Guzzo and A. M. Koekemoer and A. Leauthaud and D. Maccagni and C. Marinoni and H. J. McCracken and P. Memeo and B. Meneux and P. Oesch and L. Pozzetti and R. Scaramella},
journal= {arXiv preprint arXiv:0903.3411},
year = {2011}
}
Comments
20 pages, 19 figures, accepted for publication in ApJ