Environmental effects in the interaction and merging of galaxies in zCOSMOS

Understand

(Abridged) We analyze the environments and galactic properties (morphologies and star-formation histories) of a sample of 153 close kinematic pairs in the redshift range 0.2 < z < 1 identified in the zCOSMOS-bright 10k spectroscopic sample of galaxies.

• Correcting for projection effects, the fraction of close kinematic pairs is three times higher in the top density quartile than in the lowest one.
• This translates to a three times higher merger rate because the merger timescales are shown, from mock catalogues based on the Millennium simulation, to be largely independent of environment once the same corrections for projection is applied.
• We then examine the morphologies and stellar populations of galaxies in the pairs, comparing them to control samples that are carefully matched in environment so as to remove as much as possible the well-known effects of environment on the properties of the parent population of galaxies.