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  • 1
    Publication Date: 2013-03-01
    Description: Broad X-ray emission lines from neutral and partially ionized iron observed in active galaxies have been interpreted as fluorescence produced by the reflection of hard X-rays off the inner edge of an accretion disk. In this model, line broadening and distortion result from rapid rotation and relativistic effects near the black hole, the line shape being sensitive to its spin. Alternative models in which the distortions result from absorption by intervening structures provide an equally good description of the data, and there has been no general agreement on which is correct. Recent claims that the black hole (2 x 10(6) solar masses) at the centre of the galaxy NGC 1365 is rotating at close to its maximum possible speed rest on the assumption of relativistic reflection. Here we report X-ray observations of NGC 1365 that reveal the relativistic disk features through broadened Fe-line emission and an associated Compton scattering excess of 10-30 kiloelectronvolts. Using temporal and spectral analyses, we disentangle continuum changes due to time-variable absorption from reflection, which we find arises from a region within 2.5 gravitational radii of the rapidly spinning black hole. Absorption-dominated models that do not include relativistic disk reflection can be ruled out both statistically and on physical grounds.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Risaliti, G -- Harrison, F A -- Madsen, K K -- Walton, D J -- Boggs, S E -- Christensen, F E -- Craig, W W -- Grefenstette, B W -- Hailey, C J -- Nardini, E -- Stern, Daniel -- Zhang, W W -- England -- Nature. 2013 Feb 28;494(7438):449-51. doi: 10.1038/nature11938.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉INAF-Osservatoria Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy. risaliti@arcetri.astro.it〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23446416" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2011-09-02
    Description: The current picture of galaxy evolution advocates co-evolution of galaxies and their nuclear massive black holes, through accretion and galactic merging. Pairs of quasars, each with a massive black hole at the centre of its galaxy, have separations of 6,000 to 300,000 light years (refs 2 and 3; 1 parsec = 3.26 light years) and exemplify the first stages of this gravitational interaction. The final stages of the black-hole merging process, through binary black holes and final collapse into a single black hole with gravitational wave emission, are consistent with the sub-light-year separation inferred from the optical spectra and light-variability of two such quasars. The double active nuclei of a few nearby galaxies with disrupted morphology and intense star formation (such as NGC 6240 with a separation of about 2,600 light years and Mrk 463 with a separation of about 13,000 light years between the nuclei) demonstrate the importance of major mergers of equal-mass spiral galaxies in this evolution; such mergers lead to an elliptical galaxy, as in the case of the double-radio-nucleus elliptical galaxy 0402+379 (with a separation of about 24 light years between the nuclei). Minor mergers of a spiral galaxy with a smaller companion should be a more common occurrence, evolving into spiral galaxies with active massive black-hole pairs, but have hitherto not been seen. Here we report the presence of two active massive black holes, separated by about 490 light years, in the Seyfert galaxy NGC 3393 (50 Mpc, about 160 million light years). The regular spiral morphology and predominantly old circum-nuclear stellar population of this galaxy, and the closeness of the black holes embedded in the bulge, provide a hitherto missing observational point to the study of galaxy/black hole evolution. Comparison of our observations with current theoretical models of mergers suggests that they are the result of minor merger evolution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fabbiano, G -- Wang, Junfeng -- Elvis, M -- Risaliti, G -- England -- Nature. 2011 Aug 31;477(7365):431-4. doi: 10.1038/nature10364.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Harvard-Smithsonian Center for Astrophysics (CfA), 60 Garden Street, Cambridge, Massachusetts 02138, USA. gfabbiano@cfa.harvard.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21881560" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
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    Nature Publishing Group (NPG)
    Publication Date: 2014-03-07
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Risaliti, Guido -- England -- Nature. 2014 Mar 13;507(7491):173-4. doi: 10.1038/nature13209. Epub 2014 Mar 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉INAF-Osservatorio Astrofisico di Arcetri, 50125 Florence, Italy, and at the Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24598542" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2015-02-24
    Description: The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow's kinetic power larger than 10(46) ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nardini, E -- Reeves, J N -- Gofford, J -- Harrison, F A -- Risaliti, G -- Braito, V -- Costa, M T -- Matzeu, G A -- Walton, D J -- Behar, E -- Boggs, S E -- Christensen, F E -- Craig, W W -- Hailey, C J -- Matt, G -- Miller, J M -- O'Brien, P T -- Stern, D -- Turner, T J -- Ward, M J -- New York, N.Y. -- Science. 2015 Feb 20;347(6224):860-3. doi: 10.1126/science.1259202.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK. e.nardini@keele.ac.uk. ; Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK. Center for Space Science and Technology, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA. ; Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA. ; Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze, Italy. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA. ; INAF, Osservatorio Astronomico di Brera, Via Bianchi 46, I-23807 Merate (LC), Italy. ; Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK. ; Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA. ; Department of Physics, Technion, Haifa 32000, Israel. ; Space Science Laboratory, University of California, Berkeley, CA 94720, USA. ; Danmarks Tekniske Universitet Space-National Space Institute, Technical University of Denmark, Elektrovej 327, 2800 Lyngby, Denmark. ; Lawrence Livermore National Laboratory, Livermore, CA 94550, USA. ; Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, USA. ; Dipartimento di Matematica e Fisica, Universita degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy. ; Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA. ; Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK. ; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA. ; Physics Department, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA. Eureka Scientific Inc., 2452 Delmer Street Suite 100, Oakland, CA 94602, USA. ; Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25700515" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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