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TOPIC: Supermassive Black Holes


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Galactic mergers not the major feeding mechanism for mass monsters

A new study has obtained unexpected new insight into the feeding habits of the giant black holes, which are responsible for the emissions of some of the brightest objects in the universe: active galactic nuclei. Previous models had often assumed that mergers between galaxies are instrumental in driving matter into these black holes. But this systematic study of 1400 galaxies - the largest sample ever examined for the purpose - presents strong evidence that, at least for the past eight billion years, black holes have acquired their food more peacefully. (Astrophysical Journal, January 10, 2011)
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Key clues in the mystery behind what feeds the monstrous supermassive black holes found in virtually all galaxies have now come to light, astronomers announced. It turns out that the black holes at the hearts of the skinny, bulgeless galaxies that make up roughly half the large galaxies in the universe could grow by nibbling on gas a bit at a time, researchers suggested.
These new findings challenge notions of how galaxies evolve and how supermassive black holes influence this evolution.
Galaxies, like people, come in different shapes and sizes. There are dwarf galaxies with up to only a few billion stars, and larger ones like the Milky Way that possess hundreds of billions of stars. Many galaxies have bulges in the middle that are tightly packed with many stars, but about half of all large galaxies are bulgeless.

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Title: The Spitzer/IRAC view of black hole - bulge scaling relations
Authors: E. Sani, A. Marconi, L. K. Hunt, G. Risaliti

We present a mid-IR investigation of the scaling relations between supermassive black hole masses (MBH) and the structural parameters of the host spheroids in local galaxies. The work is based on two-dimensional bulge-disk decompositions of Spitzer/IRAC 3.6 um images of 57 galaxies with MBH estimates. Our estimates of effective radii (Re) and surface brightnesses, combined with velocity dispersions (sigma) from the literature, define a FP relation consistent with previous determinations but doubling the observed range in Re. None of our galaxies is an outlier of the FP, demonstrating the accuracy of our bulge-disk decomposition which also allows us to independently identify pseudobulges in our sample. We calibrate M/L at 3.6 um by using the tight Mdyn-Lbul relation (~0.1 dex of rms) and find that no colour corrections are required to estimate the stellar mass. The 3.6 um luminosity is thus the best tracer of Mstar yet studied. We then explore the connection between MBH and bulge structural parameters (luminosity, mass, effective radius). We find tight correlations of MBH with both 3.6 um bulge luminosity and dynamical mass (MBH/Mdyn~1/1000), with rms of ~0.35 dex, similar to the MBH-sigma relation. Our results are consistent with previous determinations at shorter wavelengths. By using our calibrated M/L, we rescale MBH-Lbul to obtain the MBH-Mstar relation, which can be used as the local reference for high-z studies which probe the cosmic evolution of MBH-galaxy relations and where the stellar mass is inferred directly from luminosity measurements. The analysis of pseudobulges shows that 4 out of 9 lie on the scaling relations within the observed scatter, while those with small MBH are significantly displaced. We explore the different origins for such behaviour, while considering the possibility of nuclear morphological components not reproduced by our two-dimensional decomposition.

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The colossal black holes at the centres of galaxies probably formed shortly after the Big Bang, a study suggests.
Some of these behemoths are billions of times more massive than our Sun.
Supercomputer simulations indicate the conditions for the birth and growth of these giants could have been set in play by the merger of galaxies when the cosmos was just a few hundred million years old.
The research, by Lucio Mayer and colleagues, is published in Nature.

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Title: Witnessing the Birth of a Quasar
Authors: Takamitsu Tanaka, Zoltán Haiman, Kristen Menou
(Version v2)

The coalescence of a supermassive black hole binary (SMBHB) is thought to be accompanied by an electromagnetic (EM) afterglow, produced by the viscous infall of the surrounding circumbinary gas disk after the merger. It has been proposed that once the merger has been detected in gravitational waves (GWs) by LISA, follow-up EM searches for this afterglow can help identify the EM counterpart of the LISA source. Here we study whether the afterglows may be sufficiently bright and numerous to be detectable in EM surveys alone. The viscous afterglow, which lasts for years to decades for SMBHBs in LISA's sensitivity window, is characterized by rapid increases in both the bolometric luminosity and in the spectral hardness of the source. If quasar activity is triggered by the same major galaxy mergers that produce SMBHBs, then the afterglow could be interpreted as a signature of the birth of a quasar. Using an idealized model for the post-merger viscous spreading of the circumbinary disk and the resulting light curve, and using the observed luminosity function of quasars as a proxy for the SMBHB merger rate, we delineate the survey requirements for identifying such birthing quasars. If circumbinary disks have a high disk surface density and viscosity, an all-sky soft X-ray survey with a sensitivity of ~10%/yr. If >1% of the X-ray emission is reprocessed into optical frequencies, birthing quasars could also be identified in optical transient surveys such as the LSST. Distinguishing a birthing quasar from other variable sources may be facilitated by the monotonic hardening of its spectrum, but will likely remain challenging. This reinforces the notion that joint EM-plus-GW observations offer the best prospects for identifying the EM signatures of SMBHB mergers.

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How do black holes eat?

Using galaxies as cosmic telescopes to reveal the diets of the black holes at the heart of every galaxy.
Anglo-Australian Observatory Astronomer David Floyd has been able to observe matter falling into a super-massive black hole - one of the Universes brightest objects.
Its the first time scientists have been able to probe so close to a supermassive black hole, a region inaccessible to telescopes until now. His work will be presented in public this week at Fresh Science - a national science talent search - at the Melbourne Museum. David is one of 16 winners from across Australia.
Material in the immediate vicinity of a black hole undergoes extreme compression and superheating. The result is a quasar, which emits so much energy as visible light, that it can outshine the galaxy in which it is located by many thousands of times.

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Survey reveals many thousands of supermassive black holes

An international team of scientists, led by Penn State Distinguished Professor Donald Schneider, has announced its completion of a massive census in which they identified the quasars in one quarter of the sky. The team's work is part of the Sloan Digital Sky Survey (SDSS), a nearly decade-long discovery-and-research effort using a 2.5 meter telescope located at Apache Point Observatory in New Mexico. The completed catalogue of quasars, which will be published in the June 2010 issue of the Astronomical Journal, includes 105,783 quasars, more than 96 percent of which were discovered by the SDSS.
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Title: The Sloan Digital Sky Survey Quasar Catalogue V. Seventh Data Release
Authors: Donald P. Schneider, Gordon T. Richards, Patrick B. Hall, Michael A. Strauss, Scott F. Anderson, Todd A. Boroson, Nicholas P. Ross, Yue Shen, W.N. Brandt, Xiaohui Fan, Naohisa Inada, Sebastian Jester, G.R. Knapp, Coleman M. Krawczyk, Anirudda R. Thakar, Daniel E. Vanden Berk, Wolfgang Voges, Brian Yanny, Donald G. York, Neta A. Bahcall, Dmitry Bizyaev, Michael R. Blanton, Howard Brewington, J. Brinkmann, Daniel Eisenstein, Joshua A. Frieman, Masataka Fukugita, Jim Gray, James E. Gunn, Pascale Hibon, Zeljko Ivezic, Stephen M. Kent, Richard G. Kron, Myung Gyoon Lee, Robert H. Lupton, Elena Malanushenko, Viktor Malanushenko, Dan Oravetz, K. Pan, Jeffrey R. Pier, Ted N. Price III, David H. Saxe, David J. Schlegel, Audry Simmons, Stephanie A. Snedden, Mark U. SubbaRao, Alexander S. Szalay, David H. Weinberg

We present the fifth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalogue, which is based upon the SDSS Seventh Data Release. The catalogue, which contains 105,783 spectroscopically confirmed quasars, represents the conclusion of the SDSS-I and SDSS-II quasar survey. The catalogue consists of the SDSS objects that have luminosities larger than M_i = -22.0 (in a cosmology with H_0 = 70 km/s/Mpc Omega_M = 0.3, and Omega_Lambda = 0.7) have at least one emission line with FWHM larger than 1000 km/s or have interesting/complex absorption features, are fainter than i > 15.0 and have highly reliable redshifts. The catalogue covers an area of 9380 deg^2. The quasar redshifts range from 0.065 to 5.46, with a median value of 1.49; the catalogue includes 1248 quasars at redshifts greater than four, of which 56 are at redshifts greater than five. The catalogue contains 9210 quasars with i < 18; slightly over half of the entries have i< 19. For each object the catalogue presents positions accurate to better than 0.1" rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalogue also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 Ang. at a spectral resolution R = 2000 the spectra can be retrieved from the SDSS public database using the information provided in the catalogue. Over 96% of the objects in the catalogue were discovered by the SDSS. We also include a supplemental list of an additional 207 quasars with SDSS spectra whose archive photometric information is incomplete.

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NASA's Swift Survey finds 'Smoking Gun' of Black Hole Activation

Data from an ongoing survey by NASA's Swift satellite have helped astronomers solve a decades-long mystery about why a small percentage of black holes emit vast amounts of energy.
Only about one percent of supermassive black holes exhibit this behaviour. The new findings confirm that black holes "light up" when galaxies collide, and the data may offer insight into the future behaviour of the black hole in our own Milky Way galaxy. The study will appear in the June 20 issue of The Astrophysical Journal Letters.

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Supermassive Black Hole
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Supermassive Black Holes May Frequently Roam Galaxy Centers

A team of astronomy researchers at Florida Institute of Technology and Rochester Institute of Technology in the United States and University of Sussex in the United Kingdom, find that the supermassive black hole (SMBH) at the centre of the most massive local galaxy (M87) is not where it was expected. Their research, conducted using the Hubble Space Telescope (HST), concludes that the SMBH in M87 is displaced from the galaxy centre.
The most likely cause for this SMBH to be off centre is a previous merger between two older, less massive, SMBHs.

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