Publication details for Professor Ian SmailCalhau, J., Sobral, D., Stroe, A., Best, P., Smail, I., Lehmer, B., Harrison, C. & 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): 303-311.
- Publication type: Journal Article
- ISSN/ISBN: 0035-8711, 1365-2966
- DOI: 10.1093/mnras/stw2295
- Further publication details on publisher web site
- Durham Research Online (DRO) - may include full text
Author(s) from Durham
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.