Chandra measurements of the distribution of mass in the luminous lensing cluster Abell 2390     

S.W. Allen  S. Ettori  A.C. Fabian 《Monthly notices of the Royal Astronomical Society》2001,324(4):877-890

We present spatially resolved X-ray spectroscopy of the luminous lensing cluster Abell 2390, using observations made with the Chandra observatory. The temperature of the X-ray gas rises with increasing radius within the central ∼ 200 kpc of the cluster, and then remains approximately isothermal, with kT =11.5_−1.6^+1.5 keV , out to the limits of the observations at r ∼1.0 Mpc . The total mass profile determined from the Chandra data has a form in good agreement with the predictions from numerical simulations. Using the parametrization of Navarro, Frenk and White, we measure a scale radius r _s∼0.8 Mpc and a concentration parameter c ∼3 . The best-fitting X-ray mass model is in good agreement with independent gravitational lensing results and optical measurements of the galaxy velocity dispersion in the cluster. The X-ray gas to total mass ratio rises with increasing radius with f _gas∼21 per cent at r =0.9 Mpc . The azimuthally averaged 0.3–7.0 keV surface brightness profile exhibits a small core radius and a clear 'break' at r ∼500 kpc , where the slope changes from S _X ∼^∝  r ^−1.5 to S _X ∼^∝  r ^−3.6 . The data for the central region of the cluster indicate the presence of a cooling flow with a mass deposition rate of 200–300 M_⊙ yr⁻¹ and an effective age of 2–3 Gyr .  相似文献   

On the observed disc temperature of accreting intermediate mass black holes     

A. C. Fabian  R. R. Ross  J. M. Miller 《Monthly notices of the Royal Astronomical Society》2004,355(2):359-362

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Magnetic fields in the Centaurus cluster     

G. B. Taylor  A. C. Fabian  S. W. Allen 《Monthly notices of the Royal Astronomical Society》2002,334(4):769-776

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The peculiar cooling flow cluster RX J0820.9+0752     

C. M. Bayer-Kim  C. S. Crawford  S. W. Allen  A. C. Edge  A. C. Fabian 《Monthly notices of the Royal Astronomical Society》2002,337(3):938-952

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Full,constrained and stochastic source inversions support evidence for volumetric changes during the Basel earthquake sequence     

Aurélie Guilhem  Fabian Walter 《Swiss Journal of Geoscience》2015,108(2-3):361-377

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Galaxy cluster mass profiles     

L. M. Voigt  A. C. Fabian 《Monthly notices of the Royal Astronomical Society》2006,368(2):518-533

Accurate measurements of the mass distribution in galaxy and cluster haloes are essential to test the cold dark matter (CDM) paradigm. The cosmological model predicts a universal shape for the density profile in all haloes, independent of halo mass. Its profile has a 'cuspy' centre, with no evidence for the constant density core. In this paper, we carry out a careful analysis of 12 galaxy clusters, using Chandra data to compute the mass distribution in each system under the assumption of hydrostatic equilibrium. Due to their low concentration, clusters provide ideal objects for studying the central cusps in dark matter haloes. The majority of the systems are consistent with the CDM model, but four objects exhibit flat inner density profiles. We suggest that the flat inner profile found for these clusters is due to an underestimation of the mass in the cluster centre (rather than any problem with the CDM model), since these objects also have a centrally peaked gas mass fraction. We discuss possible causes for erroneously low-mass measurements in the cores of some systems.  相似文献   

An explanation for the soft X-ray excess in active galactic nuclei   总被引：1，自引：0，他引：1  

J. Crummy  A. C. Fabian  L. Gallo  R. R. Ross 《Monthly notices of the Royal Astronomical Society》2006,365(4):1067-1081

We present a large sample of type 1 active galactic nuclei (AGN) spectra taken with XMM–Newton , and fit them with both the conventional model (a power law and blackbody) and the relativistically blurred photoionized disc reflection model of Ross & Fabian. We find that the disc reflection model is a better fit. The disc reflection model successfully reproduces the continuum shape, including the soft excess, of all the sources. The model also reproduces many features that would conventionally be interpreted as absorption edges. We are able to use the model to infer the properties of the sources, specifically that the majority of black holes in the sample are strongly rotating, and that there is a deficit in sources with an inclination >70°. We conclude that the disc reflection model is an important tool in the study of AGN X-ray spectra.  相似文献   

A possible line-like emission feature at 8 keV in the Seyfert 1.2 UGC 3973     

L. C. Gallo  A. C. Fabian  Th. Boller  W. Pietsch 《Monthly notices of the Royal Astronomical Society》2005,363(1):64-70

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Powerful, obscured active galactic nuclei among X-ray hard, optically dim serendipitous Chandra sources     

P. Gandhi  C. S. Crawford  A. C. Fabian  R. M. Johnstone 《Monthly notices of the Royal Astronomical Society》2004,348(2):529-550

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Broad Iron Lines in AGN and X-Ray Binaries     

A. C. Fabian 《Astrophysics and Space Science》2005,300(1-3):97-105

Several AGN and black hole X-ray binaries show a clear very broad iron line, which is strong evidence that the black holes are rapidly spinning. Detailed analysis of these objects shows that the emission line is not significantly affected by absorption and that the source variability is principally due to variation in amplitude of a power-law. Underlying this is a much less variable, relativistically-smeared, reflection-dominated, component which carries the imprint of strong gravity at a few gravitational radii. The strong gravitational light bending in these regions then explains the power-law variability as due to changes in height of the primary X-ray source above the disc. The reflection component, in particular its variability and the profile of the iron line, enables us to study the innermost regions around an accreting, spinning, black hole.  相似文献