ROSAT PSPC observations of 36 high-luminosity clusters of galaxies: constraints on the gas fraction     

S. Ettori  A. C. Fabian 《Monthly notices of the Royal Astronomical Society》1999,305(4):834-848

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Soft X-ray spectroscopy of Compton-thick Seyfert 2 galaxies with BeppoSAX     

M. Guainazzi  G. Matt  L. A. Antonelli  L. Bassani  A. C. Fabian  R. Maiolino  A. Marconi  F. Fiore  K. Iwasawa  L. Piro 《Monthly notices of the Royal Astronomical Society》1999,310(1):10-20

We present an X-ray spectroscopic study of the bright Compton-thick Seyfert 2 galaxies NGC 1068 and the Circinus Galaxy, performed with BeppoSAX . Matt et al. interpreted the spectrum above 4 keV as the superposition of Compton reflection and warm plasma scattering of the nuclear radiation. When this continuum is extrapolated downwards to 0.1 keV, further components arise. The NGC 1068 spectrum is rich in emission lines, mainly owing to K _α transitions of He-like elements from oxygen to iron, plus a K _α fluorescent line from neutral iron. If the ionized lines originate in the warm scatterer, its thermal and ionization structure must be complex. From the continuum and line properties, we estimate a column density, N _warm, of the warm scatterer less than a few×10²¹ cm⁻². In the Circinus Galaxy, the absence of highly ionized iron is consistent with a scattering medium with U _X≲5 and N _warm∼ a few×10²² cm⁻². In both cases the neutral iron line is most naturally explained as fluorescence in the medium responsible for the Compton reflection continuum. In NGC 1068 an optically thin plasma emission with kT ≃500 eV and strongly sub-solar metallicity is required, while such a component is only marginal in the Circinus Galaxy. We tentatively identify this component as emission of diffuse hot gas in the nuclear starbursts. Possible causes for the metal depletion are discussed.  相似文献   

A longer XMM–Newton look at I Zwicky 1: physical conditions and variability of the ionized absorbers     

E. Costantini  L. C. Gallo  W. N. Brandt  A. C. Fabian  Th. Boller 《Monthly notices of the Royal Astronomical Society》2007,378(3):873-880

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X-ray active galactic nuclei in the core of the Perseus cluster     

S. Santra  J. S. Sanders  A. C. Fabian 《Monthly notices of the Royal Astronomical Society》2007,382(2):895-902

We present a study of the X-ray emission from the nuclei of galaxies observed in the core of the Perseus cluster in a deep exposure with Chandra . Point sources are found coincident with the nuclei of 13 early-type galaxies, as well as the central galaxy NGC 1275. This corresponds to all galaxies brighter than M _B > −18 in the Chandra field. All of these sources have a steep power-law spectral component and four have an additional thermal component. The unabsorbed power-law luminosities in the 0.5–7.0 keV band range from 8 × 10³⁸ to 5 × 10⁴⁰ erg s⁻¹. We find no simple correlations between the K -band luminosity, or the FUV and NUV AB magnitudes of these galaxies and their X-ray properties. We have estimated the black hole masses of the nuclei using the K -band   M _BH– L _{K bol}  relation and again find no correlation between black hole mass and the X-ray luminosity. Bondi accretion on to the black holes in the galaxies with minihaloes should make them much more luminous than observed.  相似文献   

The luminous X-ray hotspot in 4C 74.26: synchrotron or inverse-Compton emission?     

M. C. Erlund  A. C. Fabian  Katherine M. Blundell  C. Moss  D. R. Ballantyne 《Monthly notices of the Royal Astronomical Society》2007,379(2):498-506

We report the discovery of an X-ray counterpart to the southern radio hotspot of the largest-known radio quasar 4C 74.26 (whose redshift is z = 0.104). Both XMM–Newton and Chandra images reveal the same significant (10 arcsec i.e. 19 kpc) offset between the X-ray hotspot and the radio hotspot imaged with MERLIN. The peak of the X-ray emission may be either due to synchrotron emission or due to inverse-Compton emission. If synchrotron emission, the hotspot represents the site of particle acceleration and the offset arises from either the jet exhibiting Scheuer's 'dentist's drill' effect or a fast spine having less momentum than the sheath surrounding it, which creates the radio hotspot. If the emission arises from the inverse-Compton process, it must be inverse-Compton scattering of the cosmic microwave background in a decelerating relativistic flow, implying that the jet is relativistic (Γ≥ 2) out to a distance of at least 800 kpc. Our analysis, including optical data from the Liverpool Telescope, rules out a background active galactic nucleus for the X-ray emission and confirms its nature as a hotspot, making it the most-X-ray-luminous hotspot detected at low redshift.  相似文献   

X-ray reflection in the narrow-line Seyfert 1 galaxy 1H 0707–495     

A. C. Fabian  G. Miniutti  L. Gallo  Th. Boller  Y. Tanaka  S. Vaughan  R. R. Ross 《Monthly notices of the Royal Astronomical Society》2004,353(4):1071-1077

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The narrow-line quasar NAB 0205 + 024 observed with XMM–Newton     

L. C. Gallo  Th. Boller  W. N. Brandt  A. C. Fabian  S. Vaughan 《Monthly notices of the Royal Astronomical Society》2004,355(2):330-335

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The effect of supernova heating on cluster properties and constraints on galaxy formation models     

K. K. S. Wu  A. C. Fabian  & P. E. J. Nulsen 《Monthly notices of the Royal Astronomical Society》1998,301(1):L20-L24

We report the detection of a 5.8 Å– 10⁴ s periodicity in the 0.5–10 keV X-ray light curve of the Seyfert galaxy IRAS 18325–5926, obtained from a 5-d ASCA observation. Nearly nine cycles of the periodic variation are seen; it shows no strong energy dependence and has an amplitude of about 15 per cent. Unlike most other well-studied Seyfert galaxies, there is no evidence for strong power-law red noise in the X-ray power spectrum of IRAS 18325–5926. Scaling from the QPOs found in Galactic black hole candidates suggests that the mass of the black hole in IRAS 18325–5926 is ∼ 6 Å– 10⁶–4 Å– 10⁷ M_⊙.  相似文献   

A ROSAT study of the cores of clusters of galaxies — I. Cooling flows in an X-ray flux-limited sample     

C. B. Peres  A. C. Fabian  A. C. Edge  S. W. Allen  R. M. Johnstone  & D. A. White 《Monthly notices of the Royal Astronomical Society》1998,298(2):416-432

This is the first part of a study of the detailed X-ray properties of the cores of nearby clusters. We have used the flux-limited sample of 55 clusters listed by Edge et al., and archival and proprietary data from the ROSAT observatory. In this paper an X-ray spatial analysis based on the surface-brightness-deprojection technique is applied to the clusters in the sample with the aim of studying their cooling flow properties. We determine the fraction of cooling flows in this sample to be 70–90 per cent, and estimate the contribution of the flow region to the cluster X-ray luminosity. We show that the luminosity within a strong cooling flow can account for up to 70 per cent of a cluster X-ray bolometric luminosity. Our analysis indicates that about 40 per cent of the clusters in the sample have flows depositing more than 100 M⊙ yr⁻¹ throughout the cooling region, and that these possibly have been undisturbed for many Gyr, confirming that cooling flows are the natural state of cluster cores. New cooling flows in the sample are presented, and previously ambiguous ones are clarified. We have constructed a catalogue of some intracluster medium properties for the clusters in this sample. The profiles of the mass deposited from cooling flows are analysed, and evidence is presented for the existence of breaks in some of the profiles. Comparison is made to recent optical and radio data. We cross-correlate our sample with the Green Bank, NVSS and FIRST surveys, and with the volume-limited sample of brightest cluster galaxies presented by Lauer &38; Postman. Although weak trends exist, no strong correlation between optical magnitude or radio power of the brightest cluster galaxy and the strength of the flow is found.  相似文献   

X-ray and radio observations of the poor cluster A3581 which hosts the radio galaxy PKS 1404 − 267     

R. M. Johnstone  A. C. Fabian  & G. B. Taylor 《Monthly notices of the Royal Astronomical Society》1998,298(3):854-860

We present new X-ray and H  I 21-cm data on the poor cluster of galaxies Abell 3581. The ASCA spectrum requires a low temperature, has a strong requirement for excess absorption and shows evidence for multi-temperature components. The ROSAT HRI image shows the strongly peaked emission indicative of a cooling flow. Despite the low temperature (∼ 1.5–2.0 keV) and low luminosity (∼ 2 × 10⁴² erg s⁻¹ in the 2–10 keV band), Abell 3581 has a mass deposition rate ∼ 80 M⊙ yr⁻¹ which is larger than found for other nearby low-luminosity objects. VLA observations in the 21-cm band set velocity width and spin temperature dependent limits on the column density of atomic hydrogen.  相似文献