1,882 research outputs found
X-ray view of four high-luminosity Swift/BAT AGN: Unveiling obscuration and reflection with Suzaku
The Swift/BAT nine-month survey observed 153 AGN, all with ultra-hard X-ray
BAT fluxes in excess of 10^-11 erg cm^-2 s^-1 and an average redshift of 0.03.
Among them, four of the most luminous BAT AGN (44.73 < Log L(BAT) < 45.31) were
selected as targets of Suzaku follow-up observations: J2246.0+3941 (3C 452),
J0407.4+0339 (3C 105), J0318.7+6828, and J0918.5+0425. The column density,
scattered/reflected emission, the properties of the Fe K line, and a possible
variability are fully analyzed. For the latter, the spectral properties from
Chandra, XMM-Newton and Swift/XRT public observations were compared with the
present Suzaku analysis. Of our sample, 3C 452 is the only certain
Compton-thick AGN candidate because of i) the high absorption and strong
Compton reflection; ii) the lack of variability; iii) the "buried" nature, i.e.
the low scattering fraction (<0.5%) and the extremely low relative [OIII]
luminosity. In contrast 3C 105 is not reflection-dominated, despite the
comparable column density, X-ray luminosity and radio morphology, but shows a
strong long-term variability in flux and scattering fraction, consistent with
the soft emission being scattered from a distant region (e.g., the narrow
emission line region). The sample presents high (>100) X-to-[OIII] luminosity
ratios, confirming the [OIII] luminosity to be affected by residual extinction
in presence of mild absorption, especially for "buried" AGN such as 3C 452.
Three of our targets are powerful FRII radio galaxies, making them the most
luminous and absorbed AGN of the BAT Seyfert survey despite the inversely
proportional N_H - L_X relation.Comment: A&A paper in press, 17 page
Fabrication and test of lightweight honeycomb sandwich structures Final report
Fabrication and testing of lightweight honeycomb sandwich structure
Optical and X-ray Properties of the Swift BAT-detected AGN
The Swift Gamma-Ray Burst satellite has detected a largely unbiased towards
absorption sample of local () AGN, based solely on their
14--195 keV flux. In the first 9 months of the survey, 153 AGN sources were
detected. The X-ray properties in the 0.3--10 keV band have been compiled and
presented based on analyses with XMM-Newton, Chandra, Suzaku, and the Swift XRT
(Winter et al. 2009). Additionally, we have compiled a sub-sample of sources
with medium resolution optical ground-based spectra from the SDSS or our own
observations at KPNO. In this sample of 60 sources, we have classified the
sources using standard emission line diagnostic plots, obtained masses for the
broad line sources through measurement of the broad H emission line, and
measured the [OIII] 5007\AA luminosity of this sample. Based on continuum fits
to the intrinsic absorption features, we have obtained clues about the stellar
populations of the host galaxies. We now present the highlights of our X-ray
and optical studies of this unique sample of local AGNs, including a comparison
of the 2--10 keV and 14--195 keV X-ray luminosities with the [OIII] 5007\AA
luminosity and the implications of our results towards measurements of
bolometric luminosities.Comment: 4 pages, 2 figures, to appear in proceedings for 'X-ray Astronomy
2009', Bologna 09/2009, AIP Conference Series, Eds. A. Comastri, M. Cappi, L.
Angelin
XMM Follow-Up Observations of Three Swift BAT-Selected Active Galactic Nuclei
We present XMM-Newton observations of three AGN taken as part of a hunt to
find very heavily obscured Compton-thick AGN. For obscuring columns greater
than 10^25 cm^-2, AGN are only visible at energies below 10 keV via
reflected/scattered radiation, characterized by a flat power-law. We therefore
selected three objects (ESO 417-G006, IRAS 05218-1212, and MCG -01-05-047) from
the Swift BAT hard X-ray survey catalog with Swift X-ray Telescope XRT 0.5-10
keV spectra with flat power-law indices as candidate Compton-thick sources for
follow-up observations with the more sensitive instruments on XMM-Newton. The
XMM spectra, however, rule out reflection-dominated models based on the
weakness of the observed Fe K-alpha lines. Instead, the spectra are well-fit by
a model of a power-law continuum obscured by a Compton-thin absorber, plus a
soft excess. This result is consistent with previous follow-up observations of
two other flat-spectrum BAT-detected AGN. Thus, out of the six AGN in the
22-month BAT catalog with apparently flat Swift XRT spectra, all five that have
had follow-up observations are not likely Compton-thick. We also present new
optical spectra of two of these objects, IRAS 05218-1212 and MCG -01-05-047.
Interestingly, though both these AGN have similar X-ray spectra, their optical
spectra are completely different, adding evidence against the simplest form of
the geometric unified model of AGN. IRAS 05218-1212 appears in the optical as a
Seyfert 1, despite the ~8.5x10^22 cm^-2 line-of-sight absorbing column
indicated by its X-ray spectrum. MCG -01-05-047's optical spectrum shows no
sign of AGN activity; it appears as a normal galaxy.Comment: 18 pages including 4 figures, accepted by Ap
The relationship between adverse childhood experiences, coping using sex, and adult sexual coercion in non-incarcerated, community-based females
Adverse childhood experiences have been associated with negative outcomes in adulthood, including sexual offending. Using a cross-sectional design, we investigated whether self-reported adverse childhood experiences related to the perpetration of coercive sexual acts among 250 females recruited from the community. Furthermore, we examined whether sexualised coping mediated any potential relationship between childhood experiences and sexual coercion. A Spearmanâs rank order correlation revealed no relationship between adverse childhood experiences and sexual coercion. However, adverse childhood experiences were significantly correlated with sexualised coping, which in turn was correlated with sexual coercion. Additionally, there was a significant but small indirect effect of adverse childhood experiences on sexual coercion through sexualised coping. Findings may help researchers to better understand the causal relationship between childhood experiences, sexual coping, and sexual coercion in females
A Hard Look at NGC 5347: Revealing a Nearby Compton-thick AGN
Current measurements show that the observed fraction of Compton-thick (CT) active galactic nuclei (AGN) is smaller than the expected values needed to explain the cosmic X-ray background. Prior fits to the X-ray spectrum of the nearby Seyfert-2 galaxy NGC 5347 (z = 0.00792, D = 35.5 Mpc ) have alternately suggested a CT and Compton-thin source. Combining archival data from Suzaku, Chandra, andâmost importantlyânew data from NuSTAR, ... See full text for complete abstrac
A population of luminous accreting black holes with hidden mergers
Major galaxy mergers are thought to play an important part in fuelling the
growth of supermassive black holes. However, observational support for this
hypothesis is mixed, with some studies showing a correlation between merging
galaxies and luminous quasars and others showing no such association. Recent
observations have shown that a black hole is likely to become heavily obscured
behind merger-driven gas and dust, even in the early stages of the merger, when
the galaxies are well separated (5 to 40 kiloparsecs). Merger simulations
further suggest that such obscuration and black-hole accretion peaks in the
final merger stage, when the two galactic nuclei are closely separated (less
than 3 kiloparsecs). Resolving this final stage requires a combination of
high-spatial-resolution infrared imaging and high-sensitivity hard-X-ray
observations to detect highly obscured sources. However, large numbers of
obscured luminous accreting supermassive black holes have been recently
detected nearby (distances below 250 megaparsecs) in X-ray observations. Here
we report high-resolution infrared observations of hard-X-ray-selected black
holes and the discovery of obscured nuclear mergers, the parent populations of
supermassive-black-hole mergers. We find that obscured luminous black holes
(bolometric luminosity higher than 2x10^44 ergs per second) show a significant
(P<0.001) excess of late-stage nuclear mergers (17.6 per cent) compared to a
sample of inactive galaxies with matching stellar masses and star formation
rates (1.1 per cent), in agreement with theoretical predictions. Using
hydrodynamic simulations, we confirm that the excess of nuclear mergers is
indeed strongest for gas-rich major-merger hosts of obscured luminous black
holes in this final stage.Comment: To appear in the 8 November 2018 issue of Nature. This is the
authors' version of the wor
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