The luminosity function of TDEs from fallback-powered emission: implications for the black hole mass function

Abstract

Tidal disruption events (TDEs), in which a star is destroyed by the gravitational field of a supermassive black hole (SMBH), are being observed at a high rate owing to the advanced state of survey science. One of the properties of TDEs that is measured with increasing statistical reliability is the TDE luminosity function, $d{\dot{N}}_{\mathrm{TDE}}/dL$, which is the TDE rate per luminosity (i.e., how many TDEs are within a given luminosity range). Here we show that if the luminous emission from a TDE is directly coupled to the rate of return of tidally destroyed debris to the SMBH, then the TDE luminosity function is in good agreement with observations and scales as $\propto L^{-2.5}$ for high luminosities, provided that the SMBH mass function $d{N}_{\bullet }/d{M}_{\bullet }$ -- the number of SMBHs ($N_{\bullet }$) per SMBH mass ($M_{\bullet }$) -- is approximately flat in the mass range over which we observe TDEs. We also show that there is a cutoff in the luminosity function at low luminosities that is a result of direct captures, and this cutoff has been tentatively observed. If $d{N}_{\bullet }/d{M}_{\bullet }$ is flat, which is in agreement with some observational campaigns, these results suggest that the fallback rate feeds the accretion rate in TDEs. Contrarily, if $d{N}_{\bullet }/d\log M_{\bullet }$ is flat, which has been found theoretically and is suggested by other observational investigations, then the emission from TDEs is likely powered by another mechanism. Future observations and more TDE statistics, provided by the Rubin Observatory/LSST, will provide additional evidence as to the reality of this tension.

7 pages, 1 figure, ApJL accepted

References in corpus (15)

• The Zwicky Transient Facility: System Overview, Performance, and First Results
• An Observational Determination of the Bolometric Quasar Luminosity Function
• Stellar disruption by a supermassive black hole: is the light curve really proportional to $t^{-5/3}$?
• A synthesis model for AGN evolution: supermassive black holes growth and feedback modes
• On the mass and luminosity functions of tidal disruption flares: rate suppression due to black hole event horizons
• The Birth of a Relativistic Jet Following the Disruption of a Star by a Cosmological Black Hole
• Cooling Envelope Model for Tidal Disruption Events
• First light from tidal disruption events
• Fallback Rates from Partial Tidal Disruption Events
• A simple and accurate prescription for the tidal disruption radius of a star and the peak accretion rate in tidal disruption events
• The Luminosity Function of Tidal Disruption Flares for the ZTF-I Survey
• The local black hole mass function derived from the M_{BH}-P and the M_{BH}-n relations
• On the impact of relativistic gravity on the rate of tidal disruption events
• Capture of non-relativistic particles in eccentric orbits by a Kerr black hole
• Simulated optical light curves of super-Eddington tidal disruption events with ZEBRA flows

Cited by in corpus (1)

• Identification of Intermediate-mass Black Hole Candidates Among a Sample of Sd Galaxies