Black hole masses of tidal disruption event host galaxies

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 host 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 × 10 5 M M BH 2 × 10 7 M . The TDE host galaxy sample is dominated by low mass black holes (∼ 10 6 M ), as expected from theoretical predictions. The blackbody peak luminosity of TDEs with M BH 10 7.1 M is consistent with the Eddington limit of the SMBH, whereas the two TDEs with M BH 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 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.

On the Mass and Luminosity Functions of Tidal Disruption Flares: Rate Suppression due to Black Hole Event Horizons

“…Our selection requirements and final sample are similar to the candidate TDF samples presented recently Wevers et al 2017). The only difference is that this earlier work used stricter requirements on either the TDF light-curve sampling (to be able to measure the decay rate) or the host brightness and Declination (to allow efficient spectroscopic follow-up).…”

A Dependence of the Tidal Disruption Event Rate on Global Stellar Surface Mass Density and Stellar Velocity Dispersion

“…In this analysis, we have restricted the TDE host-galaxy sample to those with Sérsic half-light radii (the top half of Table 3), so that we could compare them directly to the control sample. Adding the nine TDE hosts with Petrosian half-light radii, the majority of which have velocity dispersions measured by Wevers et al (2017) instead of the Portsmouth pipeline, results in consistent estimates of a =  0.86 0.15 and b = - 0.8 0.5. PS1-10jh, which has a lower  S M value than the rest of the sample, has very little effect on these estimates.…”

“…The images of SDSS J1342 and J1350 were taken 1 and 2 years prior to their spectra, respectively, but it is unknown when the TDEs occurred. SDSS J0748, on the other hand, was imaged only 4 months before its spectrum was taken, and the spectrum Wevers et al (2017), are denoted by gray circles (see Table 3). Contours represent the 25th, 50th, and 84th percentiles of the volume-weighted background galaxy distribution.…”

“…The same binomial test used previously shows that the clustering of TDE hosts in this portion of phase space is significant at s s s 5 , 5 , 3 , and s 3 , respectively. While performing the analysis described here, Wevers et al (2017) published a sample of velocity dispersions for 12 TDEs. Eight of those have SDSS imaging but do not appear in the NYU value-added catalog, in some cases because their spectra are not from the SDSS legacy survey (e.g., TDE1 and D23-H1).…”

“…However, we choose to keep these objects in our sample. Recently, Wevers et al (2017) measured velocity dispersions for 12 TDE hosts. Six of these (ASASSN14li, ASASSN14ae, PTF09ge, iPTF15af, D23-H1, and TDE1) also have Portsmouth velocity dispersions, which are consistent, even when the Portsmouth values are formally lower than the SDSS instrumental resolution.…”