The role of submillimetre galaxies in hierarchical galaxy formation

TL;DR

This study uses a semi-analytical model within the Lambda Cold Dark Matter framework to explore how submillimetre galaxies influence galaxy formation and their descendants' properties, revealing their limited contribution to total stellar mass.

Contribution

It demonstrates that SMGs, modeled with a top-heavy IMF, are progenitors of diverse galaxy types but contribute minimally to the overall stellar mass in the universe.

Findings

Most SMG descendants are bulge-dominated.

Over 50% of massive galaxies are SMG descendants.

SMGs contribute only 0.2% to present-day stellar mass.

Abstract

We study the role of submillimetre galaxies (SMGs) in the galaxy formation process in the Lambda Cold Dark Matter cosmology. We use the Baugh et al. (2005) semi-analytical model, which matches the observed SMG number counts and redshift distribution by assuming a top-heavy initial mass function (IMF) in bursts triggered by galaxy mergers. We build galaxy merger trees and follow the evolution and properties of SMGs and their descendants. Our primary sample of model SMGs consists of galaxies which had 850 mu fluxes brighter than 5 mJy at some redshift z>1. Our model predicts that the present-day descendants of such SMGs cover a wide range of stellar masses ~ 10^{10} - 10^{12} Msun/h, with a median ~ 10^{11} Msun/h, and that more than 70% of these descendants are bulge-dominated. More than 50% of present day galaxies with stellar masses larger than 7 x 10^{11} Msun/h are predicted to be descendants of such SMGs. We find that although SMGs make an important contribution to the total star formation rate at z~2, the final stellar mass produced in the submillimetre phase contributes only 0.2% of the total present-day stellar mass, and 2% of the stellar mass of SMG descendants, in stark contrast to the popular picture in which the SMG phase marks the production of the bulk of the mass of present day massive ellipticals.