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The growth of typical star-forming galaxies and their supermassive black holes across cosmic time since z~2.

Calhau, J. and Sobral, D. and Stroe, A. and Best, P. and Smail, I. and Lehmer, B. and Harrison, C. and Thomson, A. (2017) 'The growth of typical star-forming galaxies and their supermassive black holes across cosmic time since z~2.', Monthly notices of the Royal Astronomical Society., 464 (1). pp. 303-311.


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 (M˙BHM˙BH) 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). M˙BHM˙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˙BHM˙BH/SFR) is approximately constant for star-forming galaxies in the last 11 Gyr. The relatively constant M˙BHM˙BH/SFR suggests that these two quantities evolve equivalently through cosmic time and with practically no delay between the two.

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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:09 September 2016
Date deposited:10 November 2016
Date of first online publication:12 September 2016
Date first made open access:10 November 2016

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