89 research outputs found
Equatorial scattering and the structure of the broad-line region in Seyfert nuclei: evidence for a rotating disc
Original article can be found at: http://www3.interscience.wiley.com/ Copyright Royal Astronomical Society. DOI: 10.1111/j.1365-2966.2005.08895.xWe present detailed scattering models confirming that distinctive variations in polarization across the broad Hα line, which are observed in a significant fraction of type 1 Seyfert galaxies, can be understood in terms of a rotating line-emitting disc surrounded by a coplanar scattering region (the equatorial scattering region). The predicted polarization properties are: (i) averaged over wavelength, the position angle (PA) of polarization is aligned with the projected disc rotation axis and hence also with the radio source axis; (ii) the polarization PA rotates across the line profile, reaching equal but opposite (relative to the continuum PA) rotations in the blue and red wings; and (iii) the degree of polarization peaks in the line wings and passes through a minimum in the line core. We identify 11 objects that exhibit these features to different degrees. In order to reproduce the large-amplitude PA rotations observed in some cases, the scattering region must closely surround the emission disc and the latter must itself be a relatively narrow annulus â presumably the Hα-emitting zone of a larger accretion disc. Asymmetries in the polarization spectra may be attributable to several possible causes, including bulk radial infall in the equatorial scattering region, or contamination by polar scattered light. The broad Hα lines do not, in general, exhibit double-peaked profiles, suggesting that a second Hα-emitting component of the broad-line region is present, in addition to the disc.Peer reviewe
Pressed for Space: The Effects of Justification and the Printing Process on Fifteenth-Century Orthography
There is a long-held belief that, prior to the standardisation of written English, printers altered spellings to justify their type. I investigate this claim through an analysis of spelling changes in William Caxtonâs two editions of the Canterbury Talesâby examining text within one book, written by one author, and set by one compositor, the only difference between the sections of verse and the sections of prose should be the requirement for justification within the latter. Were the compositors altering spellings to justify their type, we would expect to see a greater number of altered spellings in the prose sections of text. This is not what the results of this study showâinstead there is no statistically significant difference between the frequency of spelling changes in justified and non-justified text. However, there is a significantly higher number of abbreviations introduced into the justified text. These results suggest that the compositor of Caxtonâs second edition Canterbury Tales did not change spellings to justify his type
Rapid emergence of multidrug resistant, H58-lineage Salmonella typhi in Blantyre, Malawi.
INTRODUCTION: Between 1998 and 2010, S. Typhi was an uncommon cause of bloodstream infection (BSI) in Blantyre, Malawi and it was usually susceptible to first-line antimicrobial therapy. In 2011 an increase in a multidrug resistant (MDR) strain was detected through routine bacteriological surveillance conducted at Queen Elizabeth Central Hospital (QECH). METHODS: Longitudinal trends in culture-confirmed Typhoid admissions at QECH were described between 1998-2014. A retrospective review of patient cases notes was conducted, focusing on clinical presentation, prevalence of HIV and case-fatality. Isolates of S. Typhi were sequenced and the phylogeny of Typhoid in Blantyre was reconstructed and placed in a global context. RESULTS: Between 1998-2010, there were a mean of 14 microbiological diagnoses of Typhoid/year at QECH, of which 6.8% were MDR. This increased to 67 in 2011 and 782 in 2014 at which time 97% were MDR. The disease predominantly affected children and young adults (median age 11 [IQR 6-21] in 2014). The prevalence of HIV in adult patients was 16.7% [8/48], similar to that of the general population (17.8%). Overall, the case fatality rate was 2.5% (3/94). Complications included anaemia, myocarditis, pneumonia and intestinal perforation. 112 isolates were sequenced and the phylogeny demonstrated the introduction and clonal expansion of the H58 lineage of S. Typhi. CONCLUSIONS: Since 2011, there has been a rapid increase in the incidence of multidrug resistant, H58-lineage Typhoid in Blantyre. This is one of a number of reports of the re-emergence of Typhoid in Southern and Eastern Africa. There is an urgent need to understand the reservoirs and transmission of disease and how to arrest this regional increase
The Compton shoulder of the Fe Kalpha fluorescent emission line in active galactic nuclei
We present new, high signal-to-noise ratio results from a Monte Carlo study
of the properties of the Compton shoulder of the Fe Kalpha emission line in the
toroidal X-ray reprocessor model of Murphy & Yaqoob (2009, MNRAS, 397, 1549).
The model comprehensively covers the Compton-thin to Compton-thick regimes and
we find that the variety of Compton shoulder profiles is greater than that for
both (centrally-illuminated) spherical and disk geometries. Our Monte Carlo
simulations were done with a statistical accuracy that is high enough to
reveal, for the case of an edge-on, Compton-thick torus, a new type of Compton
shoulder that is not present in the spherical or disk geometries. Such a
Compton shoulder is dominated by a narrow back-scattering feature at ~6.24 keV.
Our results also reveal a dependence of the shape of the Compton shoulder (and
its magnitude relative to the Fe Kalpha line core) on the spectral shape of the
incident X-ray continuum. We also show the effects of velocity broadening on
the Fe Kalpha line profile and find that if either the velocity width or
instrument resolution is greater than a FWHM of ~2000 km/s, the Compton
shoulder begins to become blended with the line core and the characteristic
features of the Compton shoulder become harder to resolve. In particular, at a
FWHM of ~7000 km/s the Compton shoulder is NOT resolved at all, its only
signature being a weak asymmetry in the blended line profile. Thus, CCD X-ray
detectors cannot unambiguously resolve the Compton shoulder. Our results are
freely available in a format that is suitable for direct spectral-fitting of
the continuum and line model to real data.Comment: Accepted for publication in MNRAS. 12 pages, 6 figures. Abstract is
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A Spectroscopic and Photometric Study of Short-Timescale Variability in NGC5548
Results of a ground-based optical monitoring campaign on NGC5548 in June 1998
are presented. The broad-band fluxes (U,B,V), and the spectrophotometric
optical continuum flux F_lambda(5100 A) monotonically decreased in flux while
the broad-band R and I fluxes and the integrated emission-line fluxes of Halpha
and Hbeta remained constant to within 5%. On June 22, a short continuum flare
was detected in the broad band fluxes. It had an amplitude of about ~18% and it
lasted only ~90 min. The broad band fluxes and the optical continuum
F_lambda(5100 A) appear to vary simultaneously with the EUV variations. No
reliable delay was detected for the broad optical emission lines in response to
the EUVE variations. Narrow Hbeta emission features predicted as a signature of
an accretion disk were not detected during this campaign. However, there is
marginal evidence for a faint feature at lambda = 4962 A with FWHM=~6 A
redshifted by Delta v = 1100 km/s with respect to Hbeta_narrow.Comment: 12 pages, 7 figures, accepted for publishing in A&
Author Correction: A consensus-based transparency checklist.
An amendment to this paper has been published and can be accessed via a link at the top of the paper
A useful savagery: The invention of violence in nineteenth-century England
âA Useful Savagery: The Invention of Violence in Nineteenth-Century Englandâ considers a particular configuration of attitudes toward violence that emerged in the early decades of the nineteenth century. As part of a longer-term process of emerging âsensibilities,â violence was, seemingly paradoxically, âinventedâ as a social issue while concurrently relocated in the âcivilisedâ imagination as an anti-social feature mainly of âsavageâ working-class life. The dominant way this discourse evolved was through the creation of a narrative that defined âcivilisationâ in opposition to the presumed âsavageryâ of the working classes. Although the refined classes were often distanced from the physical experience of violence, concern with violence and brutality became significant parts of social commentary aimed at a middle-class readership. While stridently redefining themselves in opposition to âbrutality,â one of the purposes of this literature was to create a new middle class and justify the expansion of state power. By the closing decades of the nineteenth century, as the working classes adopted tenets of Victorian respectability, a proliferating number of social and psychological âothersâ were identified against which âcivilisedâ thought could define itself
A Variable-Density Absorption Event in NGC 3227 mapped with Suzaku and Swift
The morphology of the circumnuclear gas accreting onto supermassive black
holes in Seyfert galaxies remains a topic of much debate. As the innermost
regions of Active Galactic Nuclei (AGN) are spatially unresolved, X-ray
spectroscopy, and in particular line-of-sight absorption variability, is a key
diagnostic to map out the distribution of gas. Observations of variable X-ray
absorption in multiple Seyferts and over a wide range of timescales indicate
the presence of clumps/clouds of gas within the circumnuclear material. Eclipse
events by clumps transiting the line of sight allow us to explore the
properties of the clumps over a wide range of radial distances from the
optical/UV Broad Line Region (BLR) to beyond the dust sublimation radius.
Time-resolved absorption events have been extremely rare so far, but suggest a
range of density profiles across Seyferts. We resolve a weeks-long absorption
event in the Seyfert NGC 3227. We examine six Suzaku and twelve Swift
observations from a 2008 campaign spanning 5 weeks. We use a model accounting
for the complex spectral interplay of three differently-ionized absorbers. We
perform time-resolved spectroscopy to discern the absorption variability
behavior. We also examine the IR-to-X-ray spectral energy distribution (SED) to
test for reddening by dust. The 2008 absorption event is due to
moderately-ionized () gas covering 90% of the line of
sight. We resolve the density profile to be highly irregular, in contrast to a
previous symmetric and centrally-peaked event mapped with RXTE in the same
object. The UV data do not show significant reddening, suggesting that the
cloud is dust-free. The 2008 campaign has revealed a transit by a filamentary,
moderately-ionized cloud of variable density that is likely located in the BLR,
and possibly part of a disk wind.Comment: Accepted for publication by A&
Bottom up ethics - neuroenhancement in education and employment
Neuroenhancement involves the use of neurotechnologies to improve cognitive, affective or behavioural functioning, where these are not judged to be clinically impaired. Questions about enhancement have become one of the key topics of neuroethics over the past decade. The current study draws on in-depth public engagement activities in ten European countries giving a bottom-up perspective on the ethics and desirability of enhancement. This informed the design of an online contrastive vignette experiment that was administered to representative samples of 1000 respondents in the ten countries and the United States. The experiment investigated how the gender of the protagonist, his or her level of performance, the efficacy of the enhancer and the mode of enhancement affected support for neuroenhancement in both educational and employment contexts. Of these, higher efficacy and lower performance were found to increase willingness to support enhancement. A series of commonly articulated claims about the individual and societal dimensions of neuroenhancement were derived from the public engagement activities. Underlying these claims, multivariate analysis identified two social values. The Societal/Protective highlights counter normative consequences and opposes the use enhancers. The Individual/Proactionary highlights opportunities and supports use. For most respondents these values are not mutually exclusive. This suggests that for many neuroenhancement is viewed simultaneously as a source of both promise and concern
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