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

Accepted version
Peer-reviewed

Type

Article

Change log

Abstract

jats:titleAbstract</jats:title> jats:pThe rate of tidal disruption events (TDEs), jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, is predicted to depend on stellar conditions near the super-massive black hole (SMBH), which are on difficult-to-measure sub-parsec scales. We test whether jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn2.gif" xlink:type="simple" /> </jats:inline-formula> depends on kpc-scale global galaxy properties, which are observable. We concentrate on stellar surface mass density, jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, and velocity dispersion, jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, which correlate with the stellar density and velocity dispersion of the stars around the SMBH. We consider 35 TDE candidates, with and without known X-ray emission. The hosts range from star-forming to quiescent to quiescent with strong Balmer absorption lines. The last (often with post-starburst spectra) are overrepresented in our sample by a factor of jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn5.gif" xlink:type="simple" /> </jats:inline-formula> or jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn6.gif" xlink:type="simple" /> </jats:inline-formula>, depending on the strength of the Hjats:italicδ</jats:italic> absorption line. For a subsample of hosts with homogeneous measurements, jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn7.gif" xlink:type="simple" /> </jats:inline-formula>–jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn8.gif" xlink:type="simple" /> </jats:inline-formula>, higher on average than for a volume-weighted control sample of Sloan Digital Sky Survey galaxies with similar redshifts and stellar masses. This is because (1) most of the TDE hosts here are quiescent galaxies, which tend to have higher jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn9.gif" xlink:type="simple" /> </jats:inline-formula> than the star-forming galaxies that dominate the control, and (2) the star-forming hosts have higher average jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn10.gif" xlink:type="simple" /> </jats:inline-formula> than the star-forming control. There is also a weak suggestion that TDE hosts have lower jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn11.gif" xlink:type="simple" /> </jats:inline-formula> than for the quiescent control. Assuming that jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn12.gif" xlink:type="simple" /> </jats:inline-formula>, and applying a statistical model to the TDE hosts and control sample, we estimate jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn13.gif" xlink:type="simple" /> </jats:inline-formula> and jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn14.gif" xlink:type="simple" /> </jats:inline-formula>. This is broadly consistent with jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaaa3fdieqn15.gif" xlink:type="simple" /> </jats:inline-formula> being tied to the dynamical relaxation of stars surrounding the SMBH.</jats:p>

Description

Keywords

black hole physics, galaxies: evolution, galaxies: nuclei

Journal Title

Astrophysical Journal

Conference Name

Journal ISSN

0004-637X
1538-4357

Volume Title

853

Publisher

American Astronomical Society