The interaction-driven starburst contribution to the cosmic star formation rate density

INAF – Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
e-mail: alessandra.lamastra@oa-roma.inaf.it

Received: 16 November 2012
Accepted: 6 February 2013

Abstract

An increasing amount of observational evidence supports the notion that there are two modes of star formation: a quiescent mode in disk-like galaxies and a starburst mode, which is generally interpreted as driven by merging. Using a semi-analytic model of galaxy formation, we derive the relative contribution to the cosmic star formation rate density of quiescently star forming and starburst galaxies, predicted under the assumption that starburst events are triggered by galaxy encounters (merging and fly-by kind) during their merging histories. We show that, within this framework, quiescently star forming galaxies dominate the cosmic star formation rate density at all redshifts. The contribution of the burst-dominated star forming galaxies increases with redshift, starting from ≲5% at low redshift (z ≲ 0.1) to ~20% at z ≥ 5. We estimated that the fraction of the final (z = 0) galaxy stellar mass that is formed through the burst component of star formation is ~10% for 10¹⁰  M_⊙ ≤ M_∗ ≤ 10^11.5  M_⊙. Selected according to their distance from the galaxy main sequence, starburst galaxies account for ~10% of the star formation rate density in the redshift interval 1.5 < z < 2.5, i.e., at the cosmic peak of the star formation activity.