[论文解读] The Obsidian model: Three regimes of black hole feedback

Douglas Rennehan, Arif Babul+2 more|arXiv (Cornell University)|Sep 27, 2023

Galaxies: Formation, Evolution, Phenomena参考文献 149被引用 8

一句话总结

论文在三种吸积状态（ADAF、薄盘/类类星体、胖盘）下建立了一个自旋与吸积率相关的辐射效率模型，并结合喷流/风的反馈，将其实现于 Simba 宇宙学数值模拟中，结果显示该模型能够再现关键的星系与晕尺度可观测量。

ABSTRACT

In theoretical models of galaxy evolution, black hole feedback is a necessary ingredient in order to explain the observed exponential decline in number density of massive galaxies. Most contemporary black hole feedback models in cosmological simulations rely on a constant radiative efficiency (usually $η\sim 0.1$) at all black hole accretion rates. We present the Obsidian sub-grid model, a synthesis model for the spin-dependent radiative efficiencies of three physical accretion rate regimes, i.e. $η= η(j, \dot{M}_\mathrm{acc})$, for use in large-volume cosmological simulations. The three regimes include: an advection dominated accretion flow ($\dot{M}_\mathrm{acc} < 0.03\,\dot{M}_\mathrm{Edd}$), a quasar-like mode ($0.03 < \dot{M}_\mathrm{acc} / \dot{M}_\mathrm{Edd} < 0.3$), and a slim disc mode ($\dot{M}_\mathrm{acc} > 0.3\,\dot{M}_\mathrm{Edd}$). Additionally, we include a large-scale powerful jet at low accretion rates. The black hole feedback model we present is a kinetic model that prescribes mass loadings but could be used in thermal models directly using the radiative efficiency. We implement the Obsidian model into the Simba galaxy evolution model to determine if it is possible to reproduce galaxy populations successfully, and provide a first calibration for further study. Using a $2 imes1024^3$ particle cosmological simulation in a $(150\,\mathrm{cMpc})^3$ volume, we found that the model is successful in reproducing the galaxy stellar mass function, black hole mass-stellar mass relationship, and stellar mass-halo mass relationship. Moving forward, this model opens new avenues for exploration of the impact of black hole feedback on galactic environments.

研究动机与目标

• motivate and quantify how SMBH spin and accretion rate influence radiative and kinetic feedback in galaxy formation.
• provide a physically motivated sub-grid model for black hole feedback linking small-scale accretion physics to large-scale galaxy evolution.
• integrate the model into the Simba simulation framework and calibrate parameters against observed galaxy, BH–MG, and halo relations.

提出的方法

• Define three accretion-regime states (ADAF, quasar-like thin disk, and slim disk) with boundary thresholds at R_upper=0.3 and R_lower=0.03 based on the accretion-rate ratio R=Mdot_BH/M_Edd, and compute state transitions as instantaneous functions of the true accretion rate.
• Adopt spin-dependent radiative efficiencies eta(j, Mdot_BH) for each regime, including a slim-disk wind with momentum loading and mass loading (psi_slim) tied to eta, wind speed, and coupling parameter.
• Model kinetic feedback via winds and jets with regime-specific coupling factors epsilon_f and jet mass loading psi_jet, ensuring continuity of eta across states.
• Derive true BH accretion rates by solving mass balance equations that couple large-scale inflow, wind outflows, and radiative/jet losses, including a cubic equation in R for the slim-disk regime and a quadratic for the ADAF regime.
• Implement the model in the Simba framework (GIZMO code) with seeding, large-scale accretion (Bondi plus cold gas inflow), and jet/wind feedback, followed by calibration in a 25 cMpc/h box across six varied parameters.

实验结果

研究问题

• RQ1 How does SMBH spin and accretion rate jointly determine radiative and kinetic feedback across different accretion regimes?
• RQ2 Can a physically motivated, spin-dependent feedback model reproduce observed galaxy stellar mass functions, BH–galaxy scaling relations, and baryon fractions in groups and clusters in a large-volume simulation?
• RQ3 What is the impact of incorporating a jet/wind kinetic component at low accretion rates on galaxy evolution and halo gas content?
• RQ4 How do transitions between ADAF, quasar-like, and slim-disk states influence BH growth and host galaxy properties over cosmic time.

主要发现

• The model reproduces the galaxy stellar mass function, the black hole–stellar mass relation, and the stellar mass–halo mass relation in a 150 cMpc)^3 volume simulation.
• It extrapolates well to galaxy groups and low-mass clusters, predicting observed baryon fractions in those systems.
• Shines in group/cluster regimes by capturing the coupling between SMBH feedback and halo gas content via regime-dependent radiative and kinetic outputs.
• The spin-dependence of eta enhances the power available for feedback in higher-spin SMBHs, affecting growth and quenching efficiency across regimes.
• Mass loading and wind/jet parameters (phi, v_wind, epsilon_f) crucially control BH growth and feedback strength, especially in the slim-disk regime.