Models of jet production in black hole systems suggest that the properties of the accretion disk-such as its mass accretion rate, inner radius, and emergent magnetic field-should drive and modulate ...the production of relativistic jets. Contemporaneous radio monitoring was done using the Arcminute MicroKelvin Array radio telescope. Two important and simple results are obtained: (1) the jet (as traced by radio flux) does not appear to be modulated by changes in the inner radius of the accretion disk and (2) the jet is sensitive to disk properties, including its flux, temperature, and ionization. Some more complex results may reveal aspects of a coupled disk-corona-jet system. The overall picture that emerges from this study is broadly consistent with some jet-focused models for black hole special energy distributions in which a relativistic plasma is accelerated at z = 10-100 GM/c super(2). We discuss these results in the context of disk-jet connections across the black hole mass scale.
The X-ray background (XRB) probably originates from the integrated X-ray emission of active galactic nuclei (AGN). Modelling of its flat spectrum implies considerable absorption in most AGN. Compton ...down-scattering means that sources in which the absorption is Compton-thick are unlikely to be major contributors to the background intensity, so the observed spectral intensity at about 30 keV is little affected by photoelectric absorption. Assuming that the intrinsic photon index of AGN is 2, we then use the 30-keV intensity of the XRB to infer the absorption-corrected energy density of the background. Soltan's argument then enables us to convert this to a mean local density in black holes, assuming an accretion efficiency of 0.1 and a mean AGN redshift of 2. The result is within a factor of 2 of that estimated by Haehnelt et al. from the optically determined black hole masses of Magorrian et al. We conclude that there is no strong need for any radiatively inefficient mode of accretion for building the masses of black holes. Furthermore, we show that the absorption model for the XRB implies that about 85 per cent of accretion power in the Universe is absorbed. This power probably emerges in the infrared bands where it can be several tens per cent of the recently inferred backgrounds there. The total power emitted by accretion is then about one fifth that of stars.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
The detection of relativistic effects in an X-ray emission line from ionized iron in the galaxy MCG-6-30-15 is discussed. The features indicate that the line most probably arises in a region between ...three and ten Schwarzschild radii from the center.
Nemaline myopathy (NM) is a rare congenital neuromuscular disorder characterized by muscle weakness and hypotonia, slow gross motor development, and decreased respiratory function. Mutations in at ...least twelve genes, all of each encode proteins that are either components of the muscle thin filament or regulate its length and stability, have been associated with NM. Mutations in Nebulin (NEB), a giant filamentous protein localized in the sarcomere, account for more than 50% of NM cases. At present, there remains a lack of understanding of whether NEB genotype influences nebulin function and NM-patient phenotypes. In addition, there is a lack of therapeutically tractable models that can enable drug discovery and address the current unmet treatment needs of patients. To begin to address these gaps, here we have characterized five new zebrafish models of NEB-related NM. These mutants recapitulate most aspects of NEB-based NM, showing drastically reduced survival, defective muscle structure, reduced contraction force, shorter thin filaments, presence of electron-dense structures in myofibers, and thickening of the Z-disks. This study represents the first extensive investigation of an allelic series of nebulin mutants, and thus provides an initial examination in pre-clinical models of potential genotype-phenotype correlations in human NEB patients. It also represents the first utilization of a set of comprehensive outcome measures in zebrafish, including correlation between molecular analyses, structural and biophysical investigations, and phenotypic outcomes. Therefore, it provides a rich source of data for future studies exploring the NM pathomechanisms, and an ideal springboard for therapy identification and development for NEB-related NM.
We analyse the spectral variability of MCG-06-30-15 with 600 k s of XMM-Newton data, including 300 k s of new data from the joint XMM-Newton and NuSTAR 2013 observational campaign. We use principal ...component analysis to find high-resolution, model-independent spectra of the different variable components of the spectrum. We find that over 99 per cent of the variability can be described by just three components, which are consistent with variations in the normalization of the power-law continuum (∼97 per cent), the photon index (∼2 per cent) and the normalization of a relativistically blurred reflection spectrum (∼0.5 per cent). We also find a fourth significant component but this is heavily diluted by noise, and we can attribute all the remaining spectral variability to noise. All three components are found to be variable on time-scales from 20 down to 1 k s, which corresponds to a distance from the central black hole of less than 70 gravitational radii. We compare these results with those derived from spectral fitting, and find them to be in very good agreement with our interpretation of the principal components. We conclude that the observed relatively weak variability in the reflected component of the spectrum of MCG-06-30-15 is due to the effects of light-bending close to the event horizon of the black hole, and demonstrate that principal component analysis is an effective tool for analysing spectral variability in this regime.
Chandra observations of Abell 2199 Johnstone, R. M.; Allen, S. W.; Fabian, A. C. ...
Monthly Notices of the Royal Astronomical Society,
10/2002, Volume:
336, Issue:
1
Journal Article
Peer reviewed
Open access
We present results from an analysis of two Chandra observations of the rich, nearby galaxy cluster Abell 2199. We find evidence (having corrected for projection effects) for radial gradients in ...temperature and metallicity in the X-ray emitting gas: the temperature drops from kT∼ 4.2 keV at R= 200 kpc to 1.6 keV within R= 5 kpc of the centre. The metallicity rises from ∼0.3 solar at R= 200 kpc to ∼0.7 solar at R= 30 kpc before dropping to 0.3 solar within the central 5 kpc. We find evidence for structure in the surface brightness distribution associated with the central radio source 3C 338. No evidence is found for the gas having a large spread in temperature at any particular location despite the cooling time being short (<109 yr) within the central ∼15 kpc. Heating and mass cooling rates are calculated for various assumptions about the state of the gas.
This paper presents the results of a detailed X-ray spectral analysis of a sample of 123 X-ray sources detected with XMM-Newton in the Lockman Hole field. This is the deepest observation carried out ...with XMM-Newton with more that 600 ks of good EPIC-pn data. We have spectra with good signal to noise ( > 500 source counts) for all objects down to 0.2-12 keV fluxes of 65 x 10-15 erg cm-2 s-1 (flux limit of 66 x 10-16 erg cm-2 s-1 in the 0.5-2 and 2-10 keV bands). At the time of the analysis, we had optical spectroscopic identifications for 60% of the sources, 46 being optical type-1 AGN and 28 optical type-2 AGN. Using a single power law model our sources' average spectral slope hardens at faint 0.5-2 keV fluxes but not at faint 2-10 keV fluxes. We have been able to explain this effect in terms of an increase in X-ray absorption at faint fluxes. We did not find in our data any evidence for the existence of a population of faint intrinsically harder sources. The average spectral slope of our sources is 61.9, with an intrinsic dispersion of 60.28. We detected X-ray absorption (F-test significance > 95%) in 37% of the sources, 610% in type-1 AGN (rest-frame NH 6 1.6 x 1021-1.2x 1022 cm-2) and 677% (rest-frame NH 6 1.5 x 1021-4x 1023 cm-2) in type-2 AGN. Using X-ray fluxes corrected for absorption, the fraction of absorbed objects and the absorbing column density distribution did not vary with X-ray flux. Our type-1 and type-2 AGN do not appear to have different continuum shapes, but the distribution of intrinsic (rest-frame) absorbing column densities is different among both classes. A significant fraction of our type-2 AGN (5 out of 28) were found to display no substantial absorption (NH < 1021 cm-2). We discuss possible interpretations to this in terms of Compton-thick AGN and intrinsic Broad Line Region properties. An emission line compatible with Fe Ka was detected in 8 sources (1 type-1 AGN, 5 type-2 AGN and 2 unidentified) with rest frame equivalent widths 120-1000 eV. However weak broad components can be easily missed in other sources by the relatively noisy data. The AGN continuum or intrinsic absorption did not depend on X-ray luminosity and/or redshift. Soft excess emission was detected in 18 objects, but only in 9 (including 4 type-1 AGN and 4 type-2 AGN) could we fit this spectral component with a black body model. The measured 0.5-2 keV luminosities of the fitted black body were not significantly different in type-1 and type-2 AGN, although the temperatures of the black body were slightly higher in type-2 AGN ( < kT > = 0.26 c 0.08) than in type-1 AGN ( < kT > = 0.09 c 0.01). For 9 sources (including 1 type-1 AGN and 3 type-2 AGN) a scattering model provided a better fit of the soft excess emission. We found that the integrated contribution from our sources to the X-ray background in the 2-7 keV band is softer (G = 1.5-1.6) than the background itself, implying that fainter sources need to be more absorbed.
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We present ALMA Cycle 4 observations of CO(1-0), CO(3-2), and {sup 13}CO(3-2) line emission in the brightest cluster galaxy (BCG) of RXJ0821+0752. This is one of the first detections of {sup 13}CO ...line emission in a galaxy cluster. Half of the CO(3-2) line emission originates from two clumps of molecular gas that are spatially offset from the galactic center. These clumps are surrounded by diffuse emission that extends 8 kpc in length. The detected {sup 13}CO emission is confined entirely to the two bright clumps, with any emission outside of this region lying below our detection threshold. Two distinct velocity components with similar integrated fluxes are detected in the {sup 12}CO spectra. The narrower component (60 km s{sup −1} FWHM) is consistent in both velocity centroid and linewidth with {sup 13}CO(3-2) emission, while the broader (130–160 km s{sup −1}), slightly blueshifted wing has no associated {sup 13}CO(3-2) emission. A simple local thermodynamic model indicates that the {sup 13}CO emission traces 2.1 × 10{sup 9} M {sub ⊙} of molecular gas. Isolating the {sup 12}CO velocity component that accompanies the {sup 13}CO emission yields a CO-to-H{sub 2} conversion factor of α {sub CO} = 2.3 M {sub ⊙} (K km s{sup −1}){sup −1}, which is a factor of two lower than the Galactic value. Adopting the Galactic CO-to-H{sub 2} conversion factor in BCGs may therefore overestimate their molecular gas masses by a factor of two. This is within the object-to-object scatter from extragalactic sources, so calibrations in a larger sample of clusters are necessary in order to confirm a sub-Galactic conversion factor.
By combining large-scale mosaics of ROSAT PSPC, XMM-Newton, and Suzaku X-ray observations, we present evidence for large-scale motions in the intracluster medium of the nearby, X-ray bright Perseus ...Cluster. These motions are suggested by several alternating and interleaved X-ray bright, low-temperature, low-entropy arcs located along the east-west axis, at radii ranging from ~ 10 kpc to over a Mpc. Thermodynamic features qualitatively similar to these have previously been observed in the centers of cool-core clusters, and were successfully modeled as a consequence of the gas sloshing/swirling motions induced by minor mergers. Our observations indicate that such sloshing/swirling can extend out to larger radii than previously thought, on scales approaching the virial radius.
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