Tidal disruption event demographics

We survey the properties of stars destroyed in tidal disruption events (TDEs) as a function of black hole (BH) mass, stellar mass and evolutionary state, star formation history and redshift. For M-BH less than or similar to 107 M-circle dot, the typical TDE is due to a M* similar to 0.3M(circle dot) M-dwarf, although the mass function is relatively flat for M* less than or similar to M-circle dot. The contribution from older main-sequence stars and sub-giants is small but not negligible. From M-BH similar to 107.5-108.5 M-circle dot, the balance rapidly shifts to higher mass stars and a larger contribution from evolved stars, and is ultimately dominated by evolved stars at higher BH masses. The star formation history has little effect until the rates are dominated by evolved stars. TDE rates should decline very rapidly towards higher redshifts. The volumetric rate of TDEs is very high because the BH mass function diverges for low masses. However, any emission mechanism which is largely Eddington-limited for low BH masses suppresses this divergence in any observed sample and leads to TDE samples dominated by M-BH similar or equal to 10(6.0)-10(7.5) M-circle dot BHs with roughly Eddington peak accretion rates. The typical fall-back time is relatively long, with 16 per cent having t(fb) < 10(-1) yr (37 d), and 84 per cent having longer time-scales. Many residual rate discrepancies can be explained if surveys are biased against TDEs with these longer t(fb), which seems very plausible if tfb has any relation to the transient rise time. For almost any BH mass function, systematic searches for fainter, faster time-scale TDEs in smaller galaxies, and longer time-scale TDEs in more massive galaxies are likely to be rewarded.