We develop semi-empirical models of the supermassive black hole and active galactic nucleus (AGN) populations, which incorporate the black hole growth implied by the observed AGN luminosity function assuming a radiative efficiency ε, and a distribution of Eddington ratios λ. By generalizing these continuity-equation models to allow a distribution P(λ|mbh,z) we are able to draw on constraints from observationally estimated P(λ) distributions and active galaxy fractions while accounting for the luminosity thresholds of observational samples. We consider models with a Gaussian distribution of log λ, and Gaussians augmented with a power-law tail to low λ. Within our framework, reproducing the high observed AGN fractions at low redshift requires a characteristic Eddington ratio λ_c that declines at late times, and matching observed Eddington ratio distributions requires P(λ) that broadens at low redshift. To reproduce the observed increase of AGN fraction with black hole or galaxy mass, we also require a λ_c that decreases with increasing black hole mass, reducing the AGN luminosity associated with the most massive black holes. Finally, achieving a good match to the high mass end of the local black hole mass function requires an increased radiative efficiency at high black hole mass. We discuss the potential impact of black hole mergers or a λ-dependent bolometric correction, and we compute evolutionary predictions for black hole and galaxy specific accretion rates. Despite the flexibility of our framework, no one model provides a good fit to all the data we consider.
One of the most pressing questions in cosmology is how the black holes (BHs) powering quasars at high redshift grow to supermassive scales within a billion years of the Big Bang. Here we show that sustained super-Eddington accretion can be achieved for BHs with Eddington fractions $f_{\rm Edd}$ > 2/$ε$, where $ε$ is the efficiency with which radiation is generated in the accretion process. In this regime, the radiation carries too little momentum to halt the accretion flow and the infalling gas traps the radiation. The BH growth then proceeds unimpeded until the gas supply is exhausted, in con…
We present constraints on the timescale of star formation variability and the correlation between star formation and host halo accretion histories of star-forming (SF) central galaxies from the scatter of the stellar-to-halo mass relation (SHMR). SF galaxies are found to have a tight relationship between their star formation rates and stellar masses on the so-called "star-forming sequence" (SFS), which characterizes their SF histories and $M_*$ growths. Meanwhile, observed SHMR constraints connect $M_*$ growth to halo accretion history. Combining these observed trends with a cosmological $N$-b…
A novel sub-grid model for super-Eddington accretion of spinning black holes in galaxy-scale simulations
ETH Zürich（苏黎世联邦理工学院）；University of Oxford（牛津大学）；University of Zurich（苏黎世大学）；University of Geneva（日内瓦大学）；Università degli Studi dell’Insubria（因斯布鲁克大学）；Ludwig-Maximilians-Universität München（慕尼黑大学）
Three-Dimensional General Relativistic Radiation Magnetohydrodynamical Simulation of Super-Eddington Accretion, using a new code HARMRAD with M1 Closure
We review and discuss theoretical studies addressing the possibility of gas accretion onto black holes occurring at rates exceeding the Eddington limit. Our focus is on the applications to the growth of black hole seeds at high redshift. We first present the general notion of Super-Eddington accretion, and then summarize the different models and numerical simulations developed to study such regime. We consider optically thick flows in accretion disks as well as in spherically symmetric envelopes, and devote particular attention to the widely adopted model based on the SLIM disk solution. While…
The role of major mergers in triggering super-Eddington accretion
Dipartimento di Fisica, “Sapienza” Università di Roma（罗马大学物理系）；INAF, Osservatorio Astronomico di Roma（罗马天文台）；INFN, Sezione Roma1（罗马第一国家核物理研究所）；Sapienza School for Advanced Studies（萨皮恩扎高等研究学院）；Como Lake Center for Astrophysics, DiSAT, Università degli Studi dell’Insubria（因苏布里亚大学迪萨特科莫湖天体物理学中心）；INFN, Sezione di Milano-Bicocca（米兰比可卡国家核物理研究所）；INAF, Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（博洛尼亚空间天体物理学与科学天文台）
In this paper, we study scenarios of the super-Eddington accretion onto black holes at high redshifts $z > 10$, which are expected to be seeds to evolve to supermassive black holes until redshift $z \sim 7$. For an initial mass, $M_{\rm BH, ini} \lesssim 2 \times 10^{3} M_{\odot}$ of a seed BH, we definitely need the super-Eddington accretion, which can be applicable to both astrophysical and primordial origins. Such an accretion disk inevitably emitted high-energy photons which had heated the cosmological plasma of the inter-galactic medium continuously from high redshifts. In this case, the …
Sapienza, Università di Roma（罗马大学）；INAF, Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；INFN, Sezione di Roma I（意大利国家核物理研究所罗马第一分部）；University of Zurich（苏黎世大学）；Sapienza School for Advanced Studies（罗马大学高等研究院）；Como Lake Center for Astrophysics, DiSAT, Università degli Studi dell’Insubria（因斯布鲁克大学DiSAT科莫湖天体物理学中心）；INFN, Sezione di Milano-Bicocca（意大利国家核物理研究所米兰比可卡分部）；INAF, Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚空间科学与天体物理观测站）
