2023ApJ...955L...6Y

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 3 yr (from 2018 October to 2021 September). We infer the black hole (BH) mass (M_BH) with host galaxy scaling relations, showing that the sample M_BH ranges from 10^5.1M_⊙ to 10^8.2M_⊙. We developed a survey efficiency corrected maximum volume method to infer the rates. The rest-frame g-band luminosity function can be well described by a broken power law of $\phi ({L}_{g})\propto {\left[{\left({L}_{g}/{L}_{\mathrm{bk}}\right)}^{0.3}+{\left({L}_{g}/{L}_{\mathrm{bk}}\right)}^{2.6}\right]}^{-1}$, with L_bk = 10^43.1 erg s^–1. In the BH mass regime of 10^5.3 ≲ (M_BH/M_⊙) ≲ 10^7.3, the TDE mass function follows $\phi ({M}_{\mathrm{BH}})\propto {M}_{\mathrm{BH}}^{-0.25}$, which favors a flat local BH mass function (${{dn}}_{\mathrm{BH}}/d\mathrm{log}{M}_{\mathrm{BH}}\approx \mathrm{constant}$). We confirm the significant rate suppression at the high-mass end (M_BH ≳ 10^7.5M_⊙), which is consistent with theoretical predictions considering direct capture of hydrogen-burning stars by the event horizon. At a host galaxy mass of M_gal ∼ 10¹⁰M_⊙, the average optical TDE rate is ≈3.2 × 10^–5 galaxy^–1 yr^–1. We constrain the optical TDE rate to be [3.7, 7.4, and 1.6] × 10^–5 galaxy^–1 yr^–1 in galaxies with red, green, and blue colors.