Reversal or no reversal: the evolution of the star formation rate-density relation up to z ∼ 1.6
Finoguenov, A.; Berta, S.; Magnelli, B.; Nordon, R.; Lutz, D.; Wuyts, S.; Altieri, B.; Aussel, H.; Cimatti, A.; Elbaz, D.; Genzel, R.; Le Floc'h, E.; Poglitsch, A.; Popesso, P.; Pozzi, F.; Cooper, M. C.; Dickinson, M.; Bauer, F. E.; Salvato, M.; Brandt, W. N.; Nandra, K.; Cappelluti, N.; Tanaka, M.; Ziparo, F.; Wilman, D.; Tacconi, L.; Mulchaey, J. S.; Biviano, A.; Fadda, D.; Portal, M. Sanchez
Germany, United Kingdom, Finland, United States, Italy, Japan, France, Spain, Israel, Chile
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, `filament-like' 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.