Galaxy growth through accretion and mergers

Abstract

Galaxies have been the main protagonist in Cosmology and the study of the Universe for almost a century. Currently, they have become an independent and major field itself. Through the use of AMIGA, an analytic model that examines galaxy formation and evolution since the dark ages, we will study the roles of accretion and mergers as two different ways for galaxies to grow. The model will provide the ratio of mass coming from mergers for several ages. This ratio will be shown according to two different variables: the stellar mass of galaxies and the age of the Universe. We see that the role of mergers increased from z ∼ 10 to z ∼ 4, and had its peak at z ≈ 5, with a value of 30%. This tendency is supported by recent studies on luminosity functions. Finally, even though mergers were the most significant process in the formation of the most massive galaxies, accretion has had the major role in galaxy growth