534 research outputs found
A multiscale regularized restoration algorithm for XMM-Newton data
We introduce a new multiscale restoration algorithm for images with few
photons counts and its use for denoising XMM data. We use a thresholding of the
wavelet space so as to remove the noise contribution at each scale while
preserving the multiscale information of the signal. Contrary to other
algorithms the signal restoration process is the same whatever the signal to
noise ratio is. Thresholds according to a Poisson noise process are indeed
computed analytically at each scale thanks to the use of the unnormalized Haar
wavelet transform. Promising preliminary results are obtained on X-ray data for
Abell 2163 with the computation of a temperature map.Comment: To appear in the Proceedings of `Galaxy Clusters and the High
Redshift Universe Observed in X-rays', XXIth Moriond Astrophysics Meeting
(March 2001), Eds. Doris Neumann et a
Proactive Risk Management : A Novel Approach to Embedding Oral Corticosteroid Stewardship into Asthma Care
Acknowledgements: G. Walter Canonica, Professor of Respiratory Medicine at the Humanitas Clinical and Research Center and Humanitas University, Milan, Italy, and Liam Heaney, Clinical Professor at Queenâs University, Belfast, Northern Ireland, presented alongside Price at the AstraZeneca-sponsored symposium, âProactive risk management: a novel approach to embedding OCS Stewardship into asthma careâ, delivered on 5th September 2022 at the ERS International Congress 2022 in Barcelona, 4thâ6th September 2022. Writing assistance for this article was provided by Rachel Danks, RSD Medical Communications Ltd, Gloucestershire, UK. This is an AstraZeneca-funded publication summarising an AstraZeneca-sponsored symposium and three posters selected by AstraZeneca. This article is intended for HCPsPeer reviewedPublisher PD
Short-course systemic corticosteroids in asthma : striking the balance between efficacy and safety
The authors thank Gillian Lavelle and Claire Twomey (Novartis Product Lifecycle Services, Dublin, Ireland) for providing scientific writing support for this article, which was funded by Novartis Pharma AG (Basel, Switzerland) in accordance with Good Publication Practice (GPP3) guidelines (www.ismpp.org/gpp3).Peer reviewedPublisher PD
The distant galaxy cluster CL0016+16: X-ray analysis up to
To study the mass distribution of galaxy clusters up to their Virial radius,
CL0016+16 seems to be a good candidate,since it is a bright massive cluster,
previously considered as being dynamically relaxed. Using XMM-Newton
observations of CL0016+16, we performed a careful X-ray background analysis,
and we detected convincingly its X-ray emission up to . We then
studied its dynamical state with a detailed 2D temperature and surface
brightness analysis of the inner part of the cluster. Using the assumption of
both spherical symmetry and hydrostatic equilibrium (HE) we can determine the
main cluster parameters: total mass, temperature profile, surface brightness
profile and -parameter. We also build a temperature map which clearly
exhibits departure from spherical symmetry in the centre. To estimate the
influence of these perturbations onto our total mass estimate, we also compute
the total mass in the framework of the HE approach, but this time with various
temperature profiles obtained in different directions. These various total mass
estimates are consistent with each other. The temperature perturbations are
clear signatures of ongoing merger activity. We also find significant residuals
after subtracting the emissivity map by a 2D -model fit. We conclude
that, although CL0016+16 shows clear signs of merger activity and departure
from spherical symmetry in the centre, its X-ray emissivity can be detected up
to and the corresponding mass can be computed directly. It
is therefore a good candidate to study cosmological scaling laws as predicted
by the theory.Comment: 11 pages, 17 figures, Accepted for publication in A&
A2163: Merger events in the hottest Abell galaxy cluster II. Subcluster accretion with galaxy-gas separation
Located at z = 0.203, A2163 is a rich galaxy cluster with an intra-cluster
medium (ICM) that exhibits extraordinary properties, including an exceptionally
high X-ray luminosity, average temperature, and a powerful and extended radio
halo. The irregular and complex morphology of its gas and galaxy structure
suggests that this cluster has recently undergone major merger events that
involve two or more cluster components. In this paper, we study the gas
structure and dynamics by means of spectral-imaging analysis of X-ray data
obtained from XMM-Newton and Chandra observations. From the evidence of a cold
front, we infer the westward motion of a cool core across the E-W elongated
atmosphere of the main cluster A2163-A. Located close to a galaxy over-density,
this gas 'bullet' appears to have been spatially separated from its galaxy (and
presumably dark matter component) as a result of high-velocity accretion.
From gas brightness and temperature profile analysis performed in two
opposite regions of the main cluster, we show that the ICM has been
adiabatically compressed behind the crossing 'bullet' possibly because of shock
heating, leading to a strong departure of the ICM from hydrostatic equilibrium
in this region. Assuming that the mass estimated from the Yx proxy best
indicates the overall mass of the system and that the western cluster sector is
in approximate hydrostatic equilibrium before subcluster accretion, we infer a
merger scenario between two subunits of mass ratio 1:4, leading to a present
total system mass of M500 . The exceptional
properties of A2163 present various similarities with those of 1E0657-56, the
so-called 'bullet-cluster'. These similarities are likely to be related to a
comparable merger scenario.Comment: A&A, in pres
Radio Source Heating in the ICM: The Example of Cygnus A
One of the most promising solutions for the cooling flow problem involves
energy injection from the central AGN. However it is still not clear how
collimated jets can heat the ICM at large scale, and very little is known
concerning the effect of radio lobe expansion as they enter into pressure
equilibrium with the surrounding cluster gas. Cygnus A is one of the best
examples of a nearby powerful radio galaxy for which the synchrotron emitting
plasma and thermal emitting intra-cluster medium can be mapped in fine detail,
and previous observations have inferred possible shock structure at the
location of the cocoon. We use new XMM-Newton observations of Cygnus A, in
combination with deep Chandra observations, to measure the temperature of the
intra-cluster medium around the expanding radio cavities. We investigate how
inflation of the cavities may relate to shock heating of the intra-cluster gas,
and whether such a mechanism is sufficient to provide enough energy to offset
cooling to the extent observed.Comment: To appear in the Proceedings of "Heating vs. Cooling in Galaxies and
Clusters of Galaxies", August 2006, Garching (Germany), Eds. H. Boehringer,
G.W. Pratt, A. Finoguenov, P. Schuecker, Springer-Verlag series "ESO
Astrophysics Symposia", p.101, in press. 8 pages, 3 multiple figure
A weak lensing analysis of the PLCK G100.2-30.4 cluster
We present a mass estimate of the Planck-discovered cluster PLCK G100.2-30.4,
derived from a weak lensing analysis of deep SUBARU griz images. We perform a
careful selection of the background galaxies using the multi-band imaging data,
and undertake the weak lensing analysis on the deep (1hr) r-band image. The
shape measurement is based on the KSB algorithm; we adopt the PSFex software to
model the Point Spread Function (PSF) across the field and correct for this in
the shape measurement. The weak lensing analysis is validated through extensive
image simulations. We compare the resulting weak lensing mass profile and total
mass estimate to those obtained from our re-analysis of XMM-Newton
observations, derived under the hypothesis of hydrostatic equilibrium. The
total integrated mass profiles are in remarkably good agreement, agreeing
within 1 across their common radial range. A mass is derived for the cluster from our weak lensing
analysis. Comparing this value to that obtained from our reanalysis of
XMM-Newton data, we obtain a bias factor of (1-b) = 0.8 0.1. This is
compatible within 1 with the value of (1-b) obtained by Planck
Collaboration XXIV from their calibration of the bias factor using
newly-available weak lensing reconstructed masses.Comment: 11 pages, 12 figures, accepted for publication on Astronomy &
Astrophysics; updates in affiliation
k-Nearest Neighbor Curves in Imaging Data Classification
Background: Lung disease quantification via medical image analysis is classically difficult. We propose a method based on normalized nearest neighborhood distance classifications for comparing individual CT scan air-trapping distributions (representing 3D segmented parenchyma). Previously, between-image comparisons were precluded by the variation inherent to parenchyma segmentations, the dimensions of which are patient- and image-specific by nature.Method: Nearest neighbor distance estimations are normalized by a theoretical distance according to the uniform distribution of air trapping. This normalization renders images (of different sizes, shapes, and/or densities) comparable. The estimated distances for the k-nearest neighbor describe the proximity of point patterns over the image. Our approach assumes and requires a defined homogeneous space; therefore, a completion pretreatment is applied beforehand.Results: Model robustness is characterized via simulation in order to verify that the required initial transformations do not bias uniformly sampled results. Additional simulations were performed to assess the discriminant power of the method for different point pattern profiles. Simulation results demonstrate that the method robustly recognizes pattern dissimilarity. Finally, the model is applied on real data for illustrative purposes.Conclusion: We demonstrate that a parenchyma-cuboid completion method provides the means of characterizing air-trapping patterns in a chosen segmentation and, importantly, comparing such patterns between patients and images
Merging history of three bimodal clusters
We present a combined X-ray and optical analysis of three bimodal galaxy
clusters selected as merging candidates at z ~ 0.1. These targets are part of
MUSIC (MUlti--Wavelength Sample of Interacting Clusters), which is a general
project designed to study the physics of merging clusters by means of
multi-wavelength observations. Observations include spectro-imaging with
XMM-Newton EPIC camera, multi-object spectroscopy (260 new redshifts), and
wide-field imaging at the ESO 3.6m and 2.2m telescopes. We build a global
picture of these clusters using X-ray luminosity and temperature maps together
with galaxy density and velocity distributions. Idealized numerical simulations
were used to constrain the merging scenario for each system. We show that A2933
is very likely an equal-mass advanced pre-merger ~ 200 Myr before the core
collapse, while A2440 and A2384 are post-merger systems ~ 450 Myr and ~1.5 Gyr
after core collapse, respectively). In the case of A2384, we detect a
spectacular filament of galaxies and gas spreading over more than 1 h^{-1} Mpc,
which we infer to have been stripped during the previous collision. The
analysis of the MUSIC sample allows us to outline some general properties of
merging clusters: a strong luminosity segregation of galaxies in recent
post-mergers; the existence of preferential axes --corresponding to the merging
directions-- along which the BCGs and structures on various scales are aligned;
the concomitance, in most major merger cases, of secondary merging or accretion
events, with groups infalling onto the main cluster, and in some cases the
evidence of previous merging episodes in one of the main components. These
results are in good agreement with the hierarchical scenario of structure
formation, in which clusters are expected to form by successive merging events,
and matter is accreted along large--scale filaments
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