The evolution of galaxy clustering since z=1

Abstract

We present results of an investigation of clustering evolution of field galaxies between a redshift of z~1 and the present epoch. The current analysis relies on a sample of ~3600 galaxies from the Calar Alto Deep Imaging Survey (CADIS). The multicolor classification and redshift determination is reliable up to I=23. The redshift distribution extends to z~1.1, the resolution is Delta cz=12000 km s^-1. Thus the amplitude of the three-dimensional correlation function has to be estimated by means of the projected correlation function w(r_p). The validity of the deprojection was tested on the Las Campanas Redshift Survey (LCRS). The LCRS also serves as ''local'' measurement. We invented a new method to overcome the influence of redshift errors on w(r_p). For evolution of the clustering strength the ansatz xi(r_com,z)proportional to (1+z)^q is used. For the galaxies as a whole the evolution parameter turns out to be q~-1.9, according to the prediction of linear theory. A formal dependency on the cosmology is presumably due to the small number of fields observed. However, the measured clustering growth clearly depends on Hubble type. At z~1 early type galaxies are already much stronger clustered, an increase with q~-1 is sufficient to explain the present day amplitude of the correlation function.