Black hole masses of tidal disruption event host galaxies

Thomas Wevers; Sjoert van Velzen; Peter G. Jonker; Nicholas C. Stone; Tiara Hung; Francesca Onori; Suvi Gezari; Nadejda Blagorodnova

doi:10.1093/mnras/stx1703

paper

Black hole masses of tidal disruption event host galaxies

arXiv:1706.08965 · doi:10.1093/mnras/stx1703

Abstract

The mass of the central black hole in a galaxy that hosted a tidal disruption event (TDE) is an important parameter in understanding its energetics and dynamics. We present the first homogeneously measured black hole masses of a complete sample of 12 optically/UV selected TDE host galaxies (down to $g_{h os t}$ $\leq$ 22 mag and $z$ =0.37) in the Northern sky. The mass estimates are based on velocity dispersion measurements, performed on late time optical spectroscopic observations. We find black hole masses in the range 3 $\times$ 10 $^{5}$ M $_{⊙}$ $\leq$ M $_{BH}$ $\leq$ 2 $\times$ 10 $^{7}$ M $_{⊙}$ . The TDE host galaxy sample is dominated by low mass black holes ( $\sim$ 10 $^{6}$ M $_{⊙}$ ), as expected from theoretical predictions. The blackbody peak luminosity of TDEs with M $_{BH}$ $\leq$ 10 $^{7.1}$ M $_{⊙}$ is consistent with the Eddington limit of the SMBH, whereas the two TDEs with M $_{BH}$ $\geq$ 10 $^{7.1}$ M $_{⊙}$ have peak luminosities below their SMBH Eddington luminosity, in line with the theoretical expectation that the fallback rate for M $_{BH}$ $\geq$ 10 $^{7.1}$ M $_{⊙}$ is sub-Eddington. In addition, our observations suggest that TDEs around lower mass black holes evolve faster. These findings corroborate the standard TDE picture in 10 $^{6}$ M $_{⊙}$ black holes. Our results imply an increased tension between observational and theoretical TDE rates. By comparing the blackbody emission radius with theoretical predictions, we conclude that the optical/UV emission is produced in a region consistent with the stream self-intersection radius of shallow encounters, ruling out a compact accretion disk as the direct origin of the blackbody radiation at peak brightness.

arXiv comment16 pages, 9 figures. Submitted to MNRAS; including minor revisions suggested by the referee

Black hole masses of tidal disruption event host galaxies

Abstract

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