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Reversal or no reversal: the evolution of the star formation rate–density relation up to z ∼ 1.6

  • Author(s): Ziparo, F
  • Popesso, P
  • Finoguenov, A
  • Biviano, A
  • Wuyts, S
  • Wilman, D
  • Salvato, M
  • Tanaka, M
  • Nandra, K
  • Lutz, D
  • Elbaz, D
  • Dickinson, M
  • Altieri, B
  • Aussel, H
  • Berta, S
  • Cimatti, A
  • Fadda, D
  • Genzel, R
  • Le Floc'h, E
  • Magnelli, B
  • Nordon, R
  • Poglitsch, A
  • Pozzi, F
  • Portal, M Sanchez
  • Tacconi, L
  • Bauer, FE
  • Brandt, WN
  • Cappelluti, N
  • Cooper, MC
  • Mulchaey, JS
  • et al.
Abstract

We investigate the evolution of the star formation rate (SFR)-density relation in the Extended Chandra Deep Field South and the Great Observatories Origin Deep Survey fields up to z ~ 1.6. In addition to the 'traditional method', in which the environment is defined according to a statistical measurement of the local galaxy density, we use a 'dynamical' approach, where galaxies are classified according to three different environment regimes: group, 'filamentlike' and field. Both methods show no evidence of an SFR-density reversal. Moreover, group galaxies show a mean SFR lower than other environments up to z ~ 1, while at earlier epochs group and field galaxies exhibit consistent levels of star formation (SF) activity. We find that processes related to a massive dark matter halo must be dominant in the suppression of the SF below z ~ 1, with respect to purely density-related processes. We confirm this finding by studying the distribution of galaxies in different environments with respect to the so-called main sequence (MS) of star-forming galaxies. Galaxies in both group and 'filament-like' environments preferentially lie below the MS up to z ~ 1, with group galaxies exhibiting lower levels of star-forming activity at a given mass. At z > 1, the star-forming galaxies in groups reside on the MS. Groups exhibit the highest fraction of quiescent galaxies up to z ~ 1, after which group, 'filament-like' and field environments have a similar mix of galaxy types. We conclude that groups are the most efficient locus for SF quenching. Thus, a fundamental difference exists between bound and unbound objects, or between dark matter haloes of different masses. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

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