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Register a new userA new way to measure supermassive black hole spin in accretion disc dominated Active Galaxies
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We show that disc continuum fitting can be used to constrain black hole spin in a subclass of Narrow Line Seyfert 1 (NLS1) AGN as their low mass and high mass accretion rate means that the disc peaks at energies just below the soft X-ray bandpass. We apply the technique to the NLS1 PG1244+026, where the optical/UV/X-ray spectrum is consistent with being dominated by a standard disc component. This gives a best estimate for black hole spin which is low, with a firm upper limit of $a_*<0.86$. This contrasts with the recent X-ray determinations of (close to) maximal black hole spin in other NLS1 based on relativistic smearing of the iron profile. While our data on PG1244+026 does not have sufficient statistics at high energy to give a good measure of black hole spin from the iron line profile, cosmological simulations predict that black holes with similar masses have similar growth histories and so should have similar spins. This suggests that there is a problem either in our understanding of disc spectra, or/and X-ray reflection or/and the evolution of black hole spin.
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We report the discovery of a luminous ultra-soft X-ray excess in a radio-loud narrow-line Seyfert1 galaxy, RXJ1633+4718, from archival ROSAT observations. The thermal temperature of this emission, when fitted with a blackbody, is as low as 32.5(+8.0,-6.0)eV. This is in remarkable contrast to the canonical temperatures of ~0.1-0.2keV found hitherto for the soft X-ray excess in active galactic nuclei (AGN), and is interestingly close to the maximum temperature predicted for a postulated accretion disc in this object. If this emission is indeed blackbody in nature, the derived luminosity [3.5(+3.3,-1.5)x10^(44)ergs/s] infers a compact emitting area with a size [~5x10^(12)cm or 0.33AU in radius] that is comparable to several times the Schwarzschild radius of a black hole at the mass estimated for this AGN (3x10^6Msun). In fact, this ultra-steep X-ray emission can be well fitted as the (Compton scattered) Wien tail of the multi-temperature blackbody emission from an optically thick accretion disc, whose parameters inferred (black hole mass and accretion rate) are in good agreement with independent estimates using optical emission line spectrum. We thus consider this feature as a signature of the long-sought X-ray radiation directly from a disc around a super-massive black hole, presenting observational evidence for a black hole accretion disc in AGN. Future observations with better data quality, together with improved independent measurements of the black hole mass, may constrain the spin of the black hole.
Supermassive black holes in galaxy centres can grow by the accretion of gas, liberating energy that might regulate star formation on galaxy-wide scales. The nature of the gaseous fuel reservoirs that power black hole growth is nevertheless largely unconstrained by observations, and is instead routinely simplified as a smooth, spherical inflow of very hot gas. Recent theory and simulations instead predict that accretion can be dominated by a stochastic, clumpy distribution of very cold molecular clouds - a departure from the hot mode accretion model - although unambiguous observational support for this prediction remains elusive. Here we report observations that reveal a cold, clumpy accretion flow towards a supermassive black hole fuel reservoir in the nucleus of the Abell 2597 Brightest Cluster Galaxy (BCG), a nearby (redshift z=0.0821) giant elliptical galaxy surrounded by a dense halo of hot plasma. Under the right conditions, thermal instabilities can precipitate from this hot gas, producing a rain of cold clouds that fall toward the galaxys centre, sustaining star formation amid a kiloparsec-scale molecular nebula that inhabits its core. The observations show that these cold clouds also fuel black hole accretion, revealing shadows cast by the molecular clouds as they move inward at about 300 kilometres per second towards the active supermassive black hole in the galaxy centre, which serves as a bright backlight. Corroborating evidence from prior observations of warmer atomic gas at extremely high spatial resolution, along with simple arguments based on geometry and probability, indicate that these clouds are within the innermost hundred parsecs of the black hole, and falling closer towards it.
The formation, accretion and growth of supermassive black holes in the early universe are investigated. The accretion rate ${dot M}$ is calculated using the Bondi accretion rate onto black holes. Starting with initial seed black holes with masses $M_{rm BH}sim 10^2-10^3M_{odot}$, the Bondi accretion rate can evolve into a supermassive black hole with masses $M_{rm BH}sim 10^9-10^{10}M_{odot}$ and with a young quasar lifetime $sim 10^5-10^6$ years by super-Eddington accretion.
Understanding the processes that drive galaxy formation and shape the observed properties of galaxies is one of the most interesting and challenging frontier problems of modern astrophysics. We now know that the evolution of galaxies is critically shaped by the energy injection from accreting supermassive black holes (SMBHs). However, it is unclear how exactly the physics of this feedback process affects galaxy formation and evolution. In particular, a major challenge is unraveling how the energy released near the SMBHs is distributed over nine orders of magnitude in distance throughout galaxies and their immediate environments. The best place to study the impact of SMBH feedback is in the hot atmospheres of massive galaxies, groups, and galaxy clusters, which host the most massive black holes in the Universe, and where we can directly image the impact of black holes on their surroundings. We identify critical questions and potential measurements that will likely transform our understanding of the physics of SMBH feedback and how it shapes galaxies, through detailed measurements of (i) the thermodynamic and velocity fluctuations in the intracluster medium (ICM) as well as (ii) the composition of the bubbles inflated by SMBHs in the centers of galaxy clusters, and their influence on the cluster gas and galaxy growth, using the next generation of high spectral and spatial resolution X-ray and microwave telescopes.
We study the disk-jet connection in supermassive black holes by investigating the properties of their optical and radio emissions utilizing the SDSS-DR7 and the NVSS catalogs. Our sample contains 7017 radio-loud quasars with detection both at 1.4~GHz and SDSS optical spectrum. Using this radio-loud quasar sample, we investigate the correlation among the jet power ($P_{rm jet}$), the bolometric disk luminosity ($L_{rm disk}$), and the black hole mass ($M_{rm BH}$) in the standard accretion disk regime. We find that the jet powers correlate with the bolometric disk luminosities as $log P_{rm jet} = (0.96pm0.012)log L_{rm disk} + (0.79 pm 0.55)$. This suggests that the jet production efficiency of $eta_{rm jet}simeq1.1_{-0.76}^{+2.6}times10^{-2}$ assuming the disk radiative efficiency of $0.1$ implying low black hole spin parameters and/or low magnetic flux for radio-loud quasars. But it can be also due to dependence of the efficiency on geometrical thickness of the accretion flow which is expected to be small for quasars accreting at the disk Eddington ratios $0.01 lesssim lambda lesssim 0.3$. This low jet production efficiency does not significantly increase even if we set the disk radiative efficiency of 0.3. We also investigate the fundamental plane in our samples among $P_{rm jet}$, $L_{rm disk}$, and $M_{rm BH}$. We could not find a statistically significant fundamental plane for radio-loud quasars in the standard accretion regime.
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