Abstract
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 disk1,2,3,4,5,6,7. 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 data8,9, and there has been no general agreement on which is correct. Recent claims10 that the black hole11,12 (2 × 106 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.
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References
Brenneman, L. W. & Reynolds, C. S. Relativistic broadening of iron emission lines in a sample of active galactic nuclei. Astrophys. J. 702, 1367–1386 (2009)
Walton, D. J., Nardini, E., Fabian, A. C., Gallo, L. C. & Reis, R. C. Suzaku observations of 'bare' active galactic nuclei. Mon. Not. R. Astron. Soc. 428, 2901–2920 (2013)
Fabian, A. C., Rees, M. J., Stella, L. & White, N. E. X-ray fluorescence from the inner disc in Cygnus X-1. Mon. Not. R. Astron. Soc. 238, 729–736 (1989)
Laor, A. Line profiles from a disk around a rotating black hole. Astrophys. J. 376, 90–94 (1991)
Brenneman, L. W. & Reynolds, C. S. Constraining black hole spin via X-ray spectroscopy. Astrophys. J. 652, 1028–1043 (2006)
Chiang, C.-Y. & Fabian, A. C. Modelling the broad-band spectra of MCG-6-30-15 with a relativistic reflection model. Mon. Not. R. Astron. Soc. 414, 2345–2353 (2011)
Fabian, A. C. et al. Broad line emission from iron K- and L-shell transitions in the active galaxy 1H0707–495. Nature 459, 540–542 (2009)
Miller, L., Turner, T. J. & Reeves, J. N. An absorption origin for the X-ray spectral variability of MCG-6-30-15. Astron. Astrophys. 483, 437–452 (2008)
Miller, L., Turner, T. J., Reeves, J. N. & Braito, V. X-ray reverberation in 1H0707–495 revisited. Mon. Not. R. Astron. Soc. 408, 1928–1935 (2010)
Brenneman, L. W., Risaliti, G., Elvis, M. & Nardini, E. An examination of the spectral variability in NGC 1365 with Suzaku. Mon. Not. R. Astron. 429, 2662–2676 (2013)
Kaspi, S. et al. The relationship between luminosity and broad-line region size in active galactic nuclei. Astrophys. J. 629, 61–71 (2005)
Schulz, H., Komossa, S., Schmitz, C. & Mücke, A. Clues on the obscured active nucleus of NGC 1365. Astron. Astrophys. 346, 764–768 (1999)
Risaliti, G. et al. Variable partial covering and a relativistic iron line in NGC 1365. Astrophys. J. 696, 160–171 (2009)
Maiolino, R. et al. “Comets” orbiting a black hole. Astron. Astrophys. 517, A47 (2010)
Risaliti, G. et al. Occultation measurement of the size of the X-ray-emitting region in the active galactic nucleus of NGC 1365. Astrophys. J. 659, L111–L114 (2007)
Jansen, F. et al. XMM-Newton observatory. I. The spacecraft and operations. Astron. Astrophys. 365, L1–L6 (2001) 10.1051/0004-6361:20000036
Harrison, F. A. et al. The Nuclear Spectroscopic Telescope Array High Energy X-Ray Mission. Astrophys. J. (submitted); http://arxiv.org/abs/1301.7307
Wang, J. et al. Imaging the circumnuclear region of NGC 1365 with Chandra. Astrophys. J. 694, 718–733 (2009)
Bassani, L. et al. A three-dimensional diagnostic diagram for Seyfert 2 galaxies: probing X-ray absorption and Compton thickness. Astrophys. J. Suppl. 121473–482 (1999)
Alonso-Herrero, A. et al. Probing the nuclear and circumnuclear activity of NGC 1365 in the infrared. Mon. Not. R. Astron. Soc. 425, 311–324 (2012)
Murphy, K. D. & Yaqoob, T. An X-ray spectral model for Compton-thick toroidal reprocessors. Mon. Not. R. Astron. Soc. 397, 1549–1562 (2009)
Miniutti, G. & Fabian, A. C. A light bending model for the X-ray temporal and spectral properties of accreting black holes. Mon. Not. R. Astron. Soc. 349, 1435–1448 (2004)
Magdziarz, P. & Zdziarski, A. Angle-dependent Compton reflection of X-rays and gamma-rays. Mon. Not. R. Astron. Soc. 273, 837–848 (1995)
Reynolds, C. S. & Fabian, A. C. Broad iron-Kα emission lines as a diagnostic of black hole spin. Astrophys. J. 675, 1048–1056 (2008)
Volonteri, M., Madau, P., Quataert, E. & Rees, M. J. The distribution and cosmic evolution of massive black hole spins. Astrophys. J. 620, 69–77 (2005)
Risaliti, G. et al. Highly ionized iron absorption lines from outflowing gas in the X-ray spectrum of NGC 1365. Astrophys. J. 630, L129–L132 (2005)
Walton, D. J., Reis, R. C. & Fabian, A. C. Explaining the hard excesses in active galactic nuclei. Mon. Not. R. Astron. Soc. 408, 601–606 (2010)
Acknowledgements
This work was supported under NASA grant number NNG08FD60C, and made use of data from the Nuclear Spectroscopic Telescope Array (NuSTAR) mission, a project led by Caltech, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software and Calibration teams for support with execution and analysis of these observations. This work also made use of observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.
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G.R. is the Principal Investigator of the XMM observations of NGC1365. He led the XMM data analysis and joint spectral analysis, modelling and interpretation of the results. F.A.H. is the Principal Investigator of NuSTAR and led observation planning, execution and participated in scientific interpretation and manuscript preparation. D.J.W. analysed NuSTAR data and participated in modelling and interpretation. K.K.M. led NuSTAR calibration analysis for NGC1365. D.S. is the NuSTAR Project Scientist and participated in definition and interpretation of the observations. B.W.G. assisted in adaptation of the NuSTAR data analysis to NGC1365. E.N. participated in XMM observations, reduction and interpretation. S.E.B., F.E.C., W.W.C., C.J.H. and W.W.Z. led efforts in design, calibration and implementation of NuSTAR. All authors participated in review of the manuscript.
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Risaliti, G., Harrison, F., Madsen, K. et al. A rapidly spinning supermassive black hole at the centre of NGC 1365. Nature 494, 449–451 (2013). https://doi.org/10.1038/nature11938
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DOI: https://doi.org/10.1038/nature11938
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