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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 H alpha-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 similar to 1-2 have black hole accretion rates (M-BH) of 0.001-0.01 M-circle dot yr(-1) and star formation rates (SFRs) of similar to 10-40 M(circle dot)yr(-1), and thus grow their stellar mass much quicker than their black hole mass (3.3 +/- 0.2 orders of magnitude faster). However, similar to 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).M-BH 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 (M-BH/SFR) is approximately constant for star-forming galaxies in the last 11 Gyr. The relatively constant. M BH/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 303
2017 January

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa Fundação para a Ciência e a Tecnologia
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