Tidal disruption event rates in galaxy merger remnants

Abstract

The rate of tidal disruption events (TDEs) depends sensitively on the stellar properties of the central galactic regions. Simulations show that galaxy mergers cause gas inflows that trigger nuclear starbursts that increase the central stellar density. Motivated by these numerical results, and by the observed over-representation of post-starburst galaxies among TDE hosts, we study the evolution of the TDE rate in high-resolution hydrodynamical simulations of a galaxy merger, in which we capture the evolution of the stellar density around the massive black holes (BHs) in the merging galaxies and in the final remnant. We post-process the simulation to obtain the TDE rate. At the second pericentre, a nuclear starburst enhances the stellar density around the BH in the least massive galaxy, leading to an enhancement of the TDE rate around the secondary BH, although the magnitude and the duration of the increase depend on the stochasticity of star formation on very small scales. The central stellar density around the primary BH remains instead fairly constant, and so is its TDE rate, until the two BHs bind and are surrounded by the same stellar environment. After the formation of the binary, the stellar density decreases, and so does the TDE rate.

The quest for dual and binary supermassive black holes: A multi-messenger view

“…This latter might reveal episodic accretion from an otherwise inactive pair to an already well established AGN, like the one recently discovered next to Cyg-A in the mid-IR (Canalizo et al, 2003) and in the radio (Perley et al, 2017). A possible form of episodic accretion is represented by TDE, that are found to occur dominantly in galaxies with post-starburst star formation history and (Zabludoff et al, 1996;French et al, 2016;Pfister et al, 2019a). The accretion rates are expected to be higher in black holes with lower masses, such as in the case of white-dwarf -intermediate-mass black hole encounters.…”

The Structure of Tidal Disruption Event Host Galaxies on Scales of Tens to Thousands of Parsecs

“…HST observations of the nearby post-starburst galaxy NGC 3156 find an unusually steep central surface brightness profile on scales close to r infl ; 18 loss cone modeling implies an elevated TDE rate matching that observed in poststarburst galaxies (Stone & van Velzen 2016). Simulations also show an increased TDE rate after a galaxy-galaxy merger due to stellar overdensities caused by the merger (Pfister et al 2019).…”

Rates of Stellar Tidal Disruption

“…The simple procedure outlined above has repeatedly been used to compute TDE rates in large galaxy samples, and at this point can be performed with the publicly available Fokker-Planck code PhaseFlow (Vasiliev 2017), as was done in, e.g. Pfister et al (2019). This basic procedure was first used, however, by Syer and Ulmer (1999), who employed an even simpler formalism (one operating in coordinate space, not integral space) to a sample of 25 galaxies with surface brightness profiles I(R) taken from Byun et al (1996) and SMBH masses taken from Magorrian et al (1998).…”