Early type galaxies have been the predominant morphological class for massive galaxies since only z~1

TL;DR

This study investigates the evolution of massive galaxy morphologies from high redshift to the present, revealing a significant increase in early-type galaxies since z~1, consistent with hierarchical formation models.

Contribution

It provides a large, multi-survey analysis of massive galaxy morphologies over a broad redshift range, confirming the dominance of early types since z~1.

Findings

Early-type galaxy fraction increased from ~20-30% at z~3 to ~70% at z=0.

Early types have been predominant for massive galaxies since only z~1.

Morphological change aligns with hierarchical galaxy formation scenarios.

Abstract

Present-day massive galaxies are composed mostly of early-type objects. It is unknown whether this was also the case at higher redshifts. In a hierarchical assembling scenario the morphological content of the massive population is expected to change with time from disk-like objects in the early Universe to spheroid-like galaxies at present. In this paper we have probed this theoretical expectation by compiling a large sample of massive (M_{stellar}>10^{11} h_{70}^{-2} M_{Sun}$) galaxies in the redshift interval 0 < z < 3. Our sample of 1082 objects comprises 207 local galaxies selected from SDSS plus 875 objects observed with the HST belonging to the POWIR/DEEP2 and GNS surveys. 639 of our objects have spectroscopic redshifts. Our morphological classification is performed as close as possible to the optical restframe according to the photometric bands available in our observations both quantitatively (using the Sersic index as a morphological proxy) and qualitative (by visual inspection). Using both techniques we find an enormous change on the dominant morphological class with cosmic time. The fraction of early-type galaxies among the massive galaxy population has changed from ~20-30% at z~3 to ~70% at z=0. Early type galaxies have been the predominant morphological class for massive galaxies since only z~1.