RESEARCH
<< back
The growth of typical star-forming galaxies and their supermassive black holes across cosmic time since z similar to 2

J. Calhau, D. Sobral, A. Stroe, P. Best, I. Smail, B. Lehmer, C. M. Harrison, A. Thomson

Abstract
Understanding galaxy formation and evolution requires studying the interplay between the growth of galaxies and the growth of their black holes across cosmic time. Here, we explore a sample of Hα-selected star-forming galaxies from the High Redshift Emission Line Survey and use the wealth of multiwavelength data in the Cosmic Evolution Survey field (X-rays, far-infrared and radio) to study the relative growth rates between typical galaxies and their central supermassive black holes, from z=2.23 to z=0. Typical star-forming galaxies at z∼1–2 have black hole accretion rates (ṀBH) of 0.001-0.01 M yr−1 and star formation rates (SFRs) of ∼10–40 M yr−1, and thus grow their stellar mass much quicker than their black hole mass (3.3±0.2 orders of magnitude faster). However, ∼3 per cent of the sample (the sources detected directly in the X-rays) show a significantly quicker growth of the black hole mass (up to 1.5 orders of magnitude quicker growth than the typical sources). ṀBH falls from z=2.23 to z=0, with the decline resembling that of SFR density or the typical SFR (SFR*). We find that the average black hole to galaxy growth (ṀBH/SFR) is approximately constant for star-forming galaxies in the last 11 Gyr. The relatively constant ṀBH/SFR suggests that these two quantities evolve equivalently through cosmic time and with practically no delay between the two.

Keywords
galaxies: evolution; galaxies: high-redshift; galaxies: star formation; cosmology: observations

Astronomy and Astrophysics
Volume 464, Number of pages 9
2017 January

>> ADS>> DOI

Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia