Related papers: Observational evidence for AGNs feedback at parsec…
The brightest steady sources of radiation in the universe, active galactic nuclei (AGN), are powered by gas accretion onto a central supermassive black hole (SMBH). The large sizes and accretion rates implicated in AGN accretion disks are…
We present near-infrared spectra of young radio quasars [P(1.4GHz) ~ 26-27 W/Hz] selected from the Wide-Field Infrared Survey Explorer. The detected objects have typical redshifts of z ~ 1.6-2.5 and bolometric luminosities ~ 10^47 erg/s.…
Active Galactic Nuclei are powered by accretion of matter onto a supermassive black hole (SMBH) of mass Mbh ~ 10^{5}-10^{9} Msun. The accretion process is indeed the most efficient mechanism for energy release we currently know of, with up…
We have calculated stationary models for accretion disks around super-massive black holes in galactic nuclei. Our models show that below a critical mass flow rate of ~3 10**-3 M_Edd advection will dominate the energy budget while above that…
(Abridged) We present a method that tracks the growth of supermassive black holes (BHs) and the feedback from AGN in cosmological simulations. Our model is a substantially modified version of the one by Springel et al. (2005). Because…
Most accreting black holes emit a substantial fraction of their luminosity in hard X-rays/soft $\gamma$-rays of up to $\sim{\rm few}\times100$ keV. The observations suggest that the radiating gas is very hot, $T>10^9$ K, and optically thin.…
AGN feedback from supermassive black holes (SMBHs) at the center of early type galaxies is commonly invoked as the explanation for the quenching of star formation in these systems. The situation is complicated by the significant amount of…
We study the gas accretion onto a supermassive black hole (SMBH) using the 3D SPH code GADGET-3 on scales of 0.1-200 pc. First we test our code with spherically symmetric, adiabatic Bondi accretion problem. We find that our simulation can…
Residual star formation at late times in early-type galaxies and their progenitors must be suppressed in order to explain the population of red, passively evolving systems we see today. Likewise, residual or newly accreted reservoirs of…
Black holes are superb sources of gravitational wave signals, for example when they are born in stellar collapse. We explore the subtleties that may emerge if mass accretion events increase significantly the mass of the black hole during…
Growing observational evidence confirms the existence of massive black holes ($M_{BH} \sim 10^9 M_{\odot}$), accreting at rates close to the Eddington limit, at very high redshifts ($z \gtrsim 6-7$) in the early Universe. Recent…
Radio lobes inflated by active galactic nuclei at the centers of clusters are a promising candidate for halting condensation in clusters with short central cooling times because they are common in such clusters. In order to test the…
We present a clustering analysis of X-ray selected AGN by compiling X-ray samples from the literature and re-estimating the dark matter (DM) halo masses of AGN in a uniform manner. We find that moderate luminosity AGN (Lx(2-10…
We analytically study the dynamical and thermal properties of the optically-thin gases at the parsec-scale when they are spherically accreted onto low luminous active galactic nuclei (LLAGNs). The falling gases are irradiated by the central…
We examine the possibility that hyper-accretion onto newly born, black holes occurs in highly intermittent, non-asymmetric fashion favorable to gravitational wave emission in a neutrino cooled disk. This picture of near-hole accretion is…
Spectral timing analyses based upon wavelet transforms provide a new means to study the variability of the X-ray emission from accreting systems, including AGN, stellar mass black holes and neutron stars, and can be used to trace the time…
The X-ray emission from bright active galactic nuclei (AGNs) is believed to originate in a hot corona lying above a cold, geometrically thin accretion disk. A highly concentrated corona located within $\sim10$ gravitational radii above the…
We present a model that explains some extreme variability phenomena observed in active galactic nuclei (AGN). In this model, an orbiting companion interacts with the accretion disk surrounding the central supermassive black hole (SMBH).…
Observational searches for intermediate-mass black holes (IMBHs; $10^2 - 10^6$ $M_\odot$) include relatively isolated dwarf galaxies. For those that host active galactic nuclei (AGNs), the IMBH nature may be discerned through the accretion…
We discuss a numerical model for black hole growth and its associated feedback processes that for the first time allows cosmological simulations of structure formation to self-consistently follow the build up of the cosmic population of…