相关论文: How Big Can a Black Hole Grow?
The largest observed supermassive black holes (SMBHs) have a mass of M_BH ~ 10^{10} M_sun, nearly independent of redshift, from the local (z~0) to the early (z>6) Universe. We suggest that the growth of SMBHs above a few 10^{10} M_sun is…
The recent discovery of luminous quasars up to a redshift z=6.43 has renewed interest in the formation of black holes massive enough to power quasars. If black holes grow by Eddington-limited gas accretion with a radiative efficiency of at…
The most massive black holes observed in the Universe weigh up to $\sim 10^{10} \, \mathrm{M_{\odot}}$, nearly independent of redshift. Reaching these final masses likely required copious accretion and several major mergers. Employing a…
With the recent discoveries of massive and highly luminous quasars at high redshifts ($z\sim7$; e.g. Mortlock et al. 2011), the question of how black holes (BHs) grow in the early Universe has been cast in a new light. In order to grow BHs…
Utilizing cosmological hydrodynamic simulations we show that there is a brief super-Eddington accretion phase in typical halos at high redshift, impervious to AGN self-regulation. However, once having attained a black hole mass of…
We consider a scenario where supermassive black holes form through direct accumulation of gas at the centre of proto-galaxies. In the first stage, the accumulated gas forms a super-massive star whose core collapses when the nuclear fuel is…
We place firm upper limits on the global accretion history of massive black holes at z>5 from the recently measured unresolved fraction of the cosmic X-ray background. The maximum allowed unresolved intensity observed at 1.5 keV implies a…
We present the spectrum of compact object masses: neutron stars and black holes that originate from single stars in different environments. In particular, we calculate the dependence of maximum black hole mass on metallicity and on some…
Luminous quasars powered by accreting supermassive black holes (SMBHs) have been found in the early Universe at $z \gtrsim 7.5$, which set a strong constraint on both the seed black hole mass and the rapid growth of the SMBHs. In this work,…
We make a case for the existence for ultra-massive black holes (UMBHs) in the Universe, but argue that there exists a likely upper limit to black hole masses of the order of $M \sim 10^{10} \msun$. We show that there are three strong lines…
We report on a calculation of the growth of the mass of supermassive black holes at galactic centers from dark matter and Eddington - limited baryonic accretion. Assuming that dark matter halos are made of fermions and harbor compact…
Black hole mass, along with mass accretion rate, is a fundamental property of active galactic nuclei. Black hole mass sets an approximate upper limit to AGN energetics via the Eddington limit. We collect and compare all AGN black hole mass…
Extremely massive black holes, with masses $M_{\rm BH} > 10^9 M_\odot$, have been observed at ever higher redshifts. These results create ever tighter constraints on the formation and growth mechanisms of early black holes. Here we show…
Super-massive black holes weighing up to $\sim 10^9 \, \mathrm{M_{\odot}}$ are in place by $z \sim 7$, when the age of the Universe is $\lesssim 1 \, \mathrm{Gyr}$. This implies a time crunch for their growth, since such high masses cannot…
There is a maximum for the gravity of a black hole in the vertical direction in the accretion disc. Outflows may probably be driven from the disc if the radiation flux of the disc is greater than a critical value corresponding to the…
We argue that supermassive black hole growth in AGN occurs via sequences of randomly--oriented accretion discs with angular momentum limited by self--gravity. These stably co-- or counter--align with the black hole spin with almost equal…
The collapse of baryons into extremely massive stars with masses exceeding 10^4 M_Sun in a small fraction of protogalaxies at z > 10 is a promising candidate for the origin of supermassive black holes, some of which grow to a billion solar…
We constrain the total accreted mass density in supermassive black holes at z>6, inferred via the upper limit derived from the integrated X-ray emission from a sample of photometrically selected galaxy candidates. Studying galaxies obtained…
Recent observations support the idea that nuclear black holes grew by gas accretion while shining as luminous quasars at high redshift, and they establish a relation of the black hole mass with the host galaxy's spheroidal stellar system.…
We present a numerical relativity study of the accretion properties of a non-spinning black hole in a cosmology driven by a scalar field. The simulations are carried out with a modified moving-puncture gauge condition suitable for…