653 research outputs found
Relativistic reflection from accretion disks in the population of Active Galactic Nuclei at z=0.5-4
We report the detection of relativistically broadened iron K alpha emission
in the X-ray spectra of AGN detected in the 4Ms CDF-S. Using the Bayesian X-ray
analysis (BXA) package, we fit 199 hard band (2-7 keV) selected sources in the
redshift range z=0.5--4 with three models: (i) an absorbed power-law, (ii) the
first model plus a narrow reflection component, and (iii) the second model with
an additional relativistic broadened reflection. The Bayesian evidence for the
full sample of sources selects the model with the additional broad component as
being 10^5 times more probable to describe the data better than the second
model. For the two brightest sources in our sample, CID 190 (z=0.734) and CID
104 (z=0.543), BXA reveals the relativistic signatures in the individual
spectra. We estimate the fraction of sources containing a broad component to be
54^{+35}_{-37}% (107/199 sources). Considering that the low signal-to-noise
ratio of some spectra prevents the detection of the broad iron K alpha line, we
infer an intrinsic fraction with broad emission of around two thirds. The
detection of relativistic signatures in the X-ray spectra of these sources
suggests that they are powered by a radiatively efficient accretion disk.
Preliminary evidence is found that the spin of the black hole is high, with a
maximally spinning Kerr BH model (a=1) providing a significantly better fit
than a Schwarzschild model (a=0). Our analysis demonstrate the potential of
X-ray spectroscopy to measure this key parameter in typical SMBH systems at the
peak of BH growth.Comment: 10 pages, 5 figures, accepted for publication in MNRA
Drug-Drug Interactions Among Hepatitis C Virus (HCV) and Human Immunodeficiency Virus (HIV) Medications
One-fourth of individuals diagnosed with the human immunodeficiency virus concomitantly have the hepatitis C virus infection. Since the discovery of highly active antiretroviral therapy, liver complications have become the leading cause of morbidity and mortality in HIV-HCV coinfected individuals. Optimal treatment in this patient population is critical, as coinfection has been linked to deterioration of both disease states. The objective of this review article is to highlight the current literature on drug-drug interactions between HIV and HCV treatments. The management of the treatment of coinfection patients has been covered extensively in numerous other publications
Remembering Daulat Singh Kothari .
When Dr Krishna of noble mien and resplendent culture puffed the last of his cigars and died suddenly in the Education Minister's room in the North Block where we were meeting for a discussion about the UGC Budget, the post of the Chairman fell vacant soon after CD Deshmukh had retired. I had run to fetch a doctor from the Health Ministry across the verandah, but the medical assistance was of no avail. In a few minutes the President, Dr Sarvepalli Radhakrishnan arrived and sadly we bade farewell to the remains of a great gentleman. The search for a new Chairman started soon, and while the one very hopeful candidate was on his way to the Prime Minister's House, Dr Radhakrishnan advised the Minister to announce the appointment of Daulat Singh Kotbari who was not in the running among several aspirants. The third Chairman of the recently constituted University Grants Commission on the lines of the British model, took office in 1961
The Austenisation of Sensibility & the Darcyfication of Jane Austen: A Reflection.
Review essay examining Jane Austen's place in literary history, and her attitudes to deeply felt emotion, unpleasant aspects of contemporary life, and sexuality. (Non-refereed article
X-ray properties of BzK-selected galaxies in the deepest X-ray fields
We investigate the X-ray properties of BzK-selected galaxies at z 2
using deep X-ray data in the Chandra Deep Field South and North (CDFS and
CDFN). Of these we directly detect in X-rays 49 sBzKs in CDFS and 32 sBzKs in
CDFN. Stacking the undetected sources also reveals a significant X-ray signal.
Investigating the X-ray detection rate and stacked flux versus the IR excess
parameter (i.e. SFRtotal/SFRUV,corr), we find no strong evidence for an
increased X-ray detection rate, or a harder X-ray spectrum in IR Excess sBzKs.
This is particularly the case when one accounts for the strong correlation
between the IR excess parameter and the bolometric IR luminosity (LIR), e.g.
when controlling for LIR, the IR Non-Excess sBzKs show a detection rate at
least as high. While both direct detections and stacking suggest that the AGN
fraction in sBzK galaxies is high, there is no clear evidence for widespread
Compton thick activity in either the sBzK population generally, or the IR
Excess sBzK subsample. The very hard X-ray signal obtained for the latter in
earlier work was most likely contaminated by a few hard X-ray sources now
directly detected in deeper X-ray data. The X-ray detection fraction of passive
BzK galaxies in our sample is if anything higher than that of sBZKs, so there
is no evidence for coeval black hole growth and star formation from X-ray
analysis of the BzK populations. Because increased AGN activity in the IR
excess population is not indicated by our X-ray analysis, it appears that the
bulk of the IR Excess sBzK population are luminous star-forming galaxies whose
SFRs are either overestimated at 24 microns, underestimated in the UV, or both.
This conclusion reinforces recent results from Herschel which show similar
effects.Comment: 17 pages, 8 Figures, 7 Table
- …