The zCOSMOS-Bright survey: the clustering of early and late galaxy morphological types since z~1

TL;DR

This study measures how the spatial clustering of early and late galaxy types at z~0.8 reveals that early types are more clustered, indicating environmental influence on galaxy evolution over cosmic time.

Contribution

First measurement of galaxy morphological clustering at z~0.8 using combined HST imaging and VLT spectroscopy, revealing evolution in clustering differences.

Findings

Early-type galaxies are more strongly clustered than late types at z~0.8.

The clustering difference between types increases from z~0.8 to z~0.

Clustering differences are more pronounced on small scales.

Abstract

We measure the spatial clustering of galaxies as a function of their morphological type at z~0.8, for the first time in a deep redshift survey with full morphological information. This is obtained by combining high-resolution HST imaging and VLT spectroscopy for about 8,500 galaxies to I_AB=22.5 with accurate spectroscopic redshifts from the zCOSMOS-Bright redshift survey. At this epoch, early-type galaxies already show a significantly stronger clustering than late-type galaxies on all probed scales. A comparison to the SDSS at z~0.1, shows that the relative clustering strength between early and late morphological classes tends to increase with cosmic time at small separations, while on large scales it shows no significant evolution since z~0.8. This suggests that most early-type galaxies had already formed in intermediate and dense environments at this epoch. Our results are consistent with a picture in which the relative clustering of different morphological types between z~1 and z~0, reflects the evolving role of environment in the morphological transformation of galaxies, on top of the global mass-driven evolution.