Tidal Disruption Event Demographics with the Zwicky Transient Facility: Volumetric Rates, Luminosity Function, and Implications for the Local Black Hole Mass Function

Abstract

We conduct a systematic tidal disruption event (TDE) demographics analysis using the largest sample of optically selected TDEs. A flux-limited, spectroscopically complete sample of 33 TDEs is constructed using the Zwicky Transient Facility over three years (from October 2018 to September 2021). We infer the black hole (BH) mass ($M_{rmBH}$) with host galaxy scaling relations, showing that the sample $M_{rmBH}$ ranges from ${10}^{5.1},M_{o}dot$ to ${10}^{8.2},M_{o}dot$. We developed a survey efficiency corrected maximum volume method to infer the rates. The rest-frame $g$-band luminosity function (LF) can be well described by a broken power-law of $phi(L_g)propto[(L_g/L_{rmbk}{)}^{0.3}+(L_g/L_{rmbk}{)}^{2.6}{]}^{-1}$, with $L_{rmbk}={10}^{43.1},rmerg,s^{-1}$. In the BH mass regime of ${10}^{5.3}lesssim(M_{rmBH}/M_{o}dot)lesssim{10}^{7.3}$, the TDE mass function follows $phi(M_{rmBH})propto{M}_{rmBH}^{-0.25}$, which favors a flat local BH mass function ($d{n}_{rmBH}/drmlog{M}_{rmBH}approxrmconstant$). We confirm the significant rate suppression at the high-mass end ($M_{rmBH}gtrsim{10}^{7.5},M_{o}dot$), which is consistent with theoretical predictions considering direct capture of hydrogen-burning stars by the event horizon. At a host galaxy mass of $M_{rmgal}sim{10}^{10},M_{o}dot$, the average optical TDE rate is $approx3.2times{10}^{-5},rmgalax{y}^{-1},y{r}^{-1}$. We constrain the optical TDE rate to be [3.7, 7.4, and 1.6$]times{10}^{-5},rmgalax{y}^{-1},y{r}^{-1}$ in galaxies with red, green, and blue colors.