Contribution of flares from tidal disruptions of stars to high-redshift AGN

¹ Département de Physique Théorique, Université de Genève, 24 quai Ernest-Ansermet, 1211 Genève 4, Switzerland
e-mail: hamsa.padmanabhan@unige.ch
² Astronomy Department, Harvard University, 60 Garden Street, Cambridge, MA 02138, USA
e-mail: aloeb@cfa.harvard.edu

Received: 31 December 2020
Accepted: 23 August 2021

Abstract

We explore the contribution of tidal disruption events (TDEs) to the flares in Active Galactic Nuclei (AGN) at high redshifts. Using the latest data available from X-ray and optical observations of high-redshift galaxies, in combination with the evolution of their central supermassive black holes, we calculate the contribution of TDE to AGNs as a function of their luminosities. We find that at low redshifts (z < 1), a few percent of all AGN with bolometric luminosities L_Bol ≲ 10⁴⁴ erg s⁻¹ may be attributable to possible TDEs. However, this fraction can significantly increase at earlier cosmic times, including up to several tens of percent of the population of AGN at z ≳ 3. TDEs may comprise a significant fraction of the Compton-Thick AGN population at z ≳ 3. The above findings motivate further calibrations with upcoming X-ray missions and spectroscopic surveys targeting TDE-AGN.