611 research outputs found
Direct Estimate of Cirrus Noise in Herschel Hi-GAL Images
In Herschel images of the Galactic plane and many star forming regions, a
major factor limiting our ability to extract faint compact sources is cirrus
confusion noise, operationally defined as the "statistical error to be expected
in photometric measurements due to confusion in a background of fluctuating
surface brightness". The histogram of the flux densities of extracted sources
shows a distinctive faint-end cutoff below which the catalog suffers from
incompleteness and the flux densities become unreliable. This empirical cutoff
should be closely related to the estimated cirrus noise and we show that this
is the case. We compute the cirrus noise directly, both on Herschel images from
which the bright sources have been removed and on simulated images of cirrus
with statistically similar fluctuations. We connect these direct estimates with
those from power spectrum analysis, which has been used extensively to predict
the cirrus noise and provides insight into how it depends on various
statistical properties and photometric operational parameters. We report
multi-wavelength power spectra of diffuse Galactic dust emission from Hi-GAL
observations at 70 to 500 microns within Galactic plane fields at l= 30 degrees
and l= 59 degrees. We find that the exponent of the power spectrum is about -3.
At 250 microns, the amplitude of the power spectrum increases roughly as the
square of the median brightness of the map and so the expected cirrus noise
scales linearly with the median brightness. Generally, the confusion noise will
be a worse problem at longer wavelengths, because of the combination of lower
angular resolution and the rising power spectrum of cirrus toward lower spatial
frequencies, but the photometric signal to noise will also depend on the
relative spectral energy distribution of the source compared to the cirrus.Comment: 4 pages (in journal), 3 figures, Astronomy and Astrophysics, accepted
for publication 13 May 201
Probing interstellar turbulence in spiral galaxies using HI power spectrum analysis
We estimate the \HI intensity fluctuation power spectrum for a sample of 18
spiral galaxies chosen from THINGS. Our analysis spans a large range of
length-scales from to across the entire
galaxy sample. We find that the power spectrum of each galaxy can be well
fitted by a power law , with an index
that varies from galaxy to galaxy. For some of the galaxies the scale-invariant
power-law power spectrum extends to length-scales that are comparable to the
size of the galaxy's disk. The distribution of is strongly peaked with
50% of the values in the range to 1.5, and a mean and standard
deviation of -1.3 and 0.5 respectively. We find no significant correlation
between and the star formation rate, dynamical mass, \HI mass or
velocity dispersion of the galaxies.
Several earlier studies that have measured the power spectrum within our
Galaxy on length-scales that are considerably smaller than have
found a power-law power spectrum with in the range to
-2.5. We propose a picture where we interpret the values in the range to -2.5 as arising from three dimensional (3D) turbulence in the
Interstellar Medium (ISM) on length-scales smaller than the galaxy's
scale-height, and we interpret the values in the range to -1.5
measured in this paper as arising from two-dimensional ISM turbulence in the
plane of the galaxy's disk. It however still remains a difficulty to explain
the small galaxy to galaxy variations in the values of measured here.Comment: 20 pages, 9 figures, 3 tables. accepted for publication in New
Astronom
Deconvolution of Images from BLAST 2005: Insight into the K3-50 and IC 5146 Star-Forming Regions
We present an implementation of the iterative flux-conserving Lucy-Richardson
(L-R) deconvolution method of image restoration for maps produced by the
Balloon-borne Large Aperture Submillimeter Telescope (BLAST). We have analyzed
its performance and convergence extensively through simulations and
cross-correlations of the deconvolved images with available highresolution
maps. We present new science results from two BLAST surveys, in the Galactic
regions K3-50 and IC 5146, further demonstrating the benefits of performing
this deconvolution.
We have resolved three clumps within a radius of 4.'5 inside the star-forming
molecular cloud containing K3-50. Combining the well-resolved dust emission map
with available multi-wavelength data, we have constrained the Spectral Energy
Distributions (SEDs) of five clumps to obtain masses (M), bolometric
luminosities (L), and dust temperatures (T). The L-M diagram has been used as a
diagnostic tool to estimate the evolutionary stages of the clumps. There are
close relationships between dust continuum emission and both 21-cm radio
continuum and 12CO molecular line emission.
The restored extended large scale structures in the Northern Streamer of IC
5146 have a strong spatial correlation with both SCUBA and high resolution
extinction images. A dust temperature of 12 K has been obtained for the central
filament. We report physical properties of ten compact sources, including six
associated protostars, by fitting SEDs to multi-wavelength data. All of these
compact sources are still quite cold (typical temperature below ~ 16 K) and are
above the critical Bonner-Ebert mass. They have associated low-power Young
Stellar Objects (YSOs). Further evidence for starless clumps has also been
found in the IC 5146 region.Comment: 13 pages, 12 Figures, 3 Table
Understanding Ricin from a Defensive Viewpoint
The toxin ricin has long been understood to have potential for criminal activity and there has been concern that it might be used as a mass-scale weapon on a military basis for at least two decades. Currently, the focus has extended to encompass terrorist activities using ricin to disrupt every day activities on a smaller scale. Whichever scenario is considered, there are features in common which need to be understood; these include the knowledge of the toxicity from ricin poisoning by the likely routes, methods for the detection of ricin in relevant materials and approaches to making an early diagnosis of ricin poisoning, in order to take therapeutic steps to mitigate the toxicity. This article will review the current situation regarding each of these stages in our collective understanding of ricin and how to defend against its use by an aggressor
Media Reporting of Health Interventions: Signs of Improvement, but Major Problems Persist
Background: Studies have persistently shown deficiencies in medical reporting by the mainstream media. We have been monitoring the accuracy and comprehensiveness of medical news reporting in Australia since mid 2004. This analysis of more than 1200 stories in the Australian media compares different types of media outlets and examines reporting trends over time. Methods and Findings: Between March 2004 and June 2008 1230 news stories were rated on a national medical news monitoring web site, Media Doctor Australia. These covered a variety of health interventions ranging from drugs, diagnostic tests and surgery to dietary and complementary therapies. Each story was independently assessed by two reviewers using ten criteria. Scores were expressed as percentages of total assessable items deemed satisfactory according to a coding guide. Analysis of variance was used to compare mean scores and Fishers exact test to compare proportions. Trends over time were analysed using un-weighted linear regression analysis. Broadsheet newspapers had the highest average satisfactory scores: 58% (95% CI 56–60%), compared with tabloid newspapers and online news outlets, 48% (95% CI 44–52) and 48% (95% CI 46–50) respectively. The lowest scores were assigned to stories broadcast by human interest/current affairs television programmes (average score 33% (95% CI 28–38)). While there was a non- significant increase in average scores for all outlets, a significant improvement was seen in the online news media: a rise of 5.1% (95%CI 1.32, 8.97; P 0.009). Statistically significant improvements were seen in coverage of the potential harms of interventions, the availability of treatment or diagnostic options, and accurate quantification of benefits. Conclusion: Although the overall quality of medical reporting in the general media remains poor, this study showed modest improvements in some areas. However, the most striking finding was the continuing very poor coverage of health news by commercial current affairs television programs
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector
A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13 TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV
Hi-GAL: The Herschel Infrared Galactic Plane Survey
Hi-GAL, the Herschel infrared Galactic Plane Survey, is an Open Time Key Project of the Herschel Space Observatory. It will make an unbiased photometric survey of the inner Galactic plane by mapping a 2° wide strip in the longitude range midlmid < 60° in five wavebands between 70 μm and 500 μm. The aim of Hi-GAL is to detect the earliest phases of the formation of molecular clouds and high-mass stars and to use the optimum combination of Herschel wavelength coverage, sensitivity, mapping strategy, and speed to deliver a homogeneous census of star-forming regions and cold structures in the interstellar medium. The resulting representative samples will yield the variation of source temperature, luminosity, mass and age in a wide range of Galactic environments at all scales from massive YSOs in protoclusters to entire spiral arms, providing an evolutionary sequence for the formation of intermediate and high-mass stars. This information is essential to the formulation of a predictive global model of the role of environment and feedback in regulating the star-formation process. Such a model is vital to understanding star formation on galactic scales and in the early universe. Hi-GAL will also provide a science legacy for decades to come with incalculable potential for systematic and serendipitous science in a wide range of astronomical fields, enabling the optimum use of future major facilities such as JWST and ALMA
Abstracts of presentations on plant protection issues at the xth international congress of virology: August 11-16,1996 Binyanei haOoma, Jerusalem, Israel Part 2 Plenary Lectures
A sub-Neptune sized planet transiting the M2.5-dwarf G 9-40: Validation with the Habitable-zone Planet Finder
We validate the discovery of a 2 Earth radii sub-Neptune-size planet around
the nearby high proper motion M2.5-dwarf G 9-40 (EPIC 212048748), using
high-precision near-infrared (NIR) radial velocity (RV) observations with the
Habitable-zone Planet Finder (HPF), precision diffuser-assisted ground-based
photometry with a custom narrow-band photometric filter, and adaptive optics
imaging. At a distance of , G 9-40b is the second closest
transiting planet discovered by K2 to date. The planet's large transit depth
(3500ppm), combined with the proximity and brightness of the host star at
NIR wavelengths (J=10, K=9.2) makes G 9-40b one of the most favorable
sub-Neptune-sized planet orbiting an M-dwarf for transmission spectroscopy with
JWST, ARIEL, and the upcoming Extremely Large Telescopes. The star is
relatively inactive with a rotation period of 29 days determined from the
K2 photometry. To estimate spectroscopic stellar parameters, we describe our
implementation of an empirical spectral matching algorithm using the
high-resolution NIR HPF spectra. Using this algorithm, we obtain an effective
temperature of K, and metallicity of
. Our RVs, when coupled with the orbital
parameters derived from the transit photometry, exclude planet masses above
with 99.7% confidence assuming a circular orbit. From its
radius, we predict a mass of and an RV
semi-amplitude of , making its mass
measurable with current RV facilities. We urge further RV follow-up
observations to precisely measure its mass, to enable precise transmission
spectroscopic measurements in the future.Comment: Accepted for publication in AJ, 22 pages, 15 figure
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