The dominant role of mergers in the size evolution of massive early-type galaxies since z ∼ 1

Abstract

Aims.The role of galaxy mergers in massive galaxy evolution, and in particular to mass assembly and size growth, remains an open question. In this paper we measure the merger fraction and rate, both minor and major, of massive early-type galaxies (M* = 1011 M·) in the COSMOS field, and study their role in mass and size evolution. Methods.We used the 30-band photometric catalogue in COSMOS, complemented with the spectroscopy of the zCOSMOS survey, to define close pairs with a separation on the sky plane 10 h-1 kpc ≤ rp = 30 h-1 kpc and a relative velocity δ v 500 km s-1 in redshift space. We measured both major (stellar mass ratio μ = M*,2/M*,1 = 1/4) and minor (1/10 = μ.