Work

The growth of typical star-forming galaxies and their supermassive black holes across cosmic time sincez∼ 2

Year: 2016

Type: article

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 (⁠| $\dot{M}_{\rm BH}$ |⁠) 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). | $\dot{M}_{\rm BH}$ | 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 (⁠| $\dot{M}_{\rm BH}$ |/SFR) is approximately constant for star-forming galaxies in the last 11 Gyr. The relatively constant | $\dot{M}_{\rm BH}$ |/SFR suggests that these two quantities evolve equivalently through cosmic time and with practically no delay between the two.

Source: Monthly Notices of the Royal Astronomical Society

DOI: 10.1093/mnras/stw2295