[論文レビュー] Tidal Disruption Event Demographics with the Zwicky Transient Facility: Volumetric Rates, Luminosity Function, and Implications for the Local Black Hole Mass Function

Yuhan Yao, Vikram Ravi+27 more|arXiv (Cornell University)|Mar 12, 2023

Pulsars and Gravitational Waves Research被引用数 14

ひとこと要約

この論文は ZTF からの flux-limited でスペクトロスコピー的に完全集の optically selected TDE のサンプル33個を構築し、rest-frame g-band 光度関数と TDE に由来するブラックホール質量関数を推定し、局所のブラックホール集団への影響を論じている。

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 ($M_{ m BH}$) with host galaxy scaling relations, showing that the sample $M_{ m BH}$ ranges from $10^{5.1}\,M_\odot$ to $10^{8.2}\,M_\odot$. 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 $ϕ(L_g)\propto [(L_g / L_{ m bk})^{0.3} + (L_g / L_{ m bk})^{2.6}]^{-1}$, with $L_{ m bk}=10^{43.1}\,{ m erg\,s^{-1}}$. In the BH mass regime of $10^{5.3}\lesssim (M_{ m BH}/M_\odot) \lesssim 10^{7.3}$, the TDE mass function follows $ϕ(M_{ m BH})\propto M_{ m BH}^{-0.25}$, which favors a flat local BH mass function ($dn_{ m BH}/d{ m log}M_{ m BH}\approx{ m constant}$). We confirm the significant rate suppression at the high-mass end ($M_{ m BH}\gtrsim 10^{7.5}\,M_\odot$), which is consistent with theoretical predictions considering direct capture of hydrogen-burning stars by the event horizon. At a host galaxy mass of $M_{ m gal}\sim 10^{10}\,M_\odot$, the average optical TDE rate is $\approx 3.2 imes 10^{-5}\,{ m galaxy^{-1}\,yr^{-1}}$. We constrain the optical TDE rate to be [3.7, 7.4, and 1.6$] imes 10^{-5}\,{ m galaxy^{-1}\,yr^{-1}}$ in galaxies with red, green, and blue colors.

研究の動機と目的

• Construct a flux-limited, spectroscopically complete sample of optically selected TDEs from ZTF over 3 years.
• Infer black hole masses for host galaxies using scaling relations and characterize the BH mass range.
• Derive the rest-frame g-band luminosity function of TDEs and fit its shape.
• Compute TDE volumetric rates as a function of BH mass and host properties, including color dependence.
• Discuss implications for the local black hole mass function and Hills mass-related suppression at high BH masses.

提案手法

• Retrospective, multi-step filtering of ZTF nuclear transients to build a complete TDE candidate sample.
• Apply survey efficiency corrections via a maximum-volume method to infer volumetric rates.
• Perform UV/optical light-curve fitting to characterize TDE energetics and timescales.
• Obtain host galaxy properties and estimate M_BH using scaling relations.
• Assess spectroscopic completeness and quantify rates in red, green, and blue host galaxies.

実験結果

リサーチクエスチョン

• RQ1 What is the rest-frame optical (g-band) luminosity function of optically selected TDEs?
• RQ2 What is the volumetric TDE rate as a function of black hole mass, and does it show suppression at high M_BH as predicted by Hills mass considerations?
• RQ3 How does the TDE mass function constrain the local black hole mass function (BHMF) and its shape at low masses?
• RQ4 How do host galaxy properties (e.g., color, mass) influence the optical TDE rate?

主な発見

• The sample comprises 33 TDEs with BH masses spanning roughly 10^5.1 to 10^8.2 solar masses.
• The rest-frame g-band luminosity function is well described by a broken power law: phi(L_g) ∝ [(L_g/L_bk)^0.3 + (L_g/L_bk)^2.6]^{-1} with L_bk = 10^43.1 erg s^-1.
• In the BH mass range 10^5.3 ≲ M_BH/M_sun ≲ 10^7.3, the TDE mass function follows phi(M_BH) ∝ M_BH^(-0.25), favoring a roughly flat local BH mass function in dN_BH/dlog M_BH.
• There is a significant rate suppression at the high-mass end (M_BH ≳ 10^7.5 M_sun), consistent with direct capture expectations at the event horizon.
• “Average” optical TDE rate near M_gal ~ 10^10 M_sun is ~3.2×10^-5 galaxy^-1 yr^-1, with constrained rates in red, green, and blue hosts: [3.7, 7.4, 1.6]×10^-5 galaxy^-1 yr^-1 respectively.