ZCOSMOS 20k: Satellite galaxies are the main drivers of environmental effects in the galaxy population at least to z ~ 0.7

K. Kovač, S. J. Lilly, C. Knobel, T. J. Bschorr, Y. Peng, C. M. Carollo, T. Contini, J. P. Kneib, O. Le Févre, V. Mainieri, A. Renzini, M. Scodeggio, G. Zamorani, S. Bardelli, M. Bolzonella, A. Bongiorno, K. Caputi, O. Cucciati, S. de la Torre, L. de RavelP. Franzetti, B. Garilli, A. Iovino, P. Kampczyk, F. Lamareille, J. F. Le Borgne, V. Le Brun, C. Maier, M. Mignoli, P. Oesch, R. Pello, E. Perez Montero, V. Presotto, J. Silverman, M. Tanaka, L. Tasca, L. Tresse, D. Vergani, E. Zucca, H. Aussel, A. M. Koekemoer, E. Le Floc'h, M. Moresco, L. Pozzetti

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76 Citations (Scopus)


We explore the role of environment in the evolution of galaxies over 0.1 < z < 0.7 using the final zCOSMOS-bright data set. Using the red fraction of galaxies as a proxy for the quenched population, we find that the fraction of red galaxies increases with the environmental overdensity δ and with the stellar mass M*, consistent with previous works. As at lower redshift, the red fraction appears to be separable in mass and environment, suggesting the action of two processes: mass εm(M*) and environmental ερ(δ) quenching. The parameters describing these appear to be essentially the same at z ∼ 0.7 as locally. We explore the relation between red fraction, mass and environment also for the central and satellite galaxies separately, paying close attention to the effects of impurities in the central-satellite classification and using carefully constructed samples well matched in stellar mass. There is little evidence for a dependence of the red fraction of centrals on overdensity. Satellites are consistently redder at all overdensities, and the satellite quenching efficiency, εsat(δ, M*), increases with overdensity at 0.1 < z < 0.4. This is less marked at higher redshift, but both are nevertheless consistent with the equivalent local measurements. At a given stellar mass, the fraction of galaxies that are satellites, fsat(δ, M*), also increases with overdensity. The obtained ερ(δ)/fsat(δ, M*) agrees well with εsat(δ, M*), demonstrating that the environmental quenching in the overall population is consistent with being entirely produced by a satellite quenching process at least up to z = 0.7. However, despite the unprecedented size of our high-redshift samples, the associated statistical uncertainties are still significant and our statements should be understood as approximations to physical reality, rather than physically exact formulae.

Original languageEnglish
Pages (from-to)717-738
Number of pages22
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - 2014 Feb


  • Cosmology: observations
  • Galaxies: evolution
  • Galaxies: groups: general
  • Galaxies: star formation
  • Galaxies: statistics


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