311 research outputs found
The XMM-LSS survey: the Class 1 cluster sample over the extended 11 deg and its spatial distribution
This paper presents 52 X-ray bright galaxy clusters selected within the 11
deg XMM-LSS survey. 51 of them have spectroscopic redshifts
(), one is identified at , and all together make
the high-purity "Class 1" (C1) cluster sample of the XMM-LSS, the highest
density sample of X-ray selected clusters with a monitored selection function.
Their X-ray fluxes, averaged gas temperatures (median keV),
luminosities (median ergs/s) and total mass
estimates (median ) are measured, adapting to
the specific signal-to-noise regime of XMM-LSS observations. The redshift
distribution of clusters shows a deficit of sources when compared to the
cosmological expectations, regardless of whether WMAP-9 or Planck-2013 CMB
parameters are assumed. This lack of sources is particularly noticeable at . However, after quantifying uncertainties due to small
number statistics and sample variance we are not able to put firm (i.e. ) constraints on the presence of a large void in the cluster
distribution. We work out alternative hypotheses and demonstrate that a
negative redshift evolution in the normalization of the relation
(with respect to a self-similar evolution) is a plausible explanation for the
observed deficit. We confirm this evolutionary trend by directly studying how
C1 clusters populate the space, properly accounting for selection
biases. We point out that a systematically evolving, unresolved, central
component in clusters and groups (AGN contamination or cool core) can impact
the classification as extended sources and be partly responsible for the
observed redshift distribution.[abridged]Comment: 33 pages, 21 figures, 3 tables ; accepted for publication in MNRA
Cardiac protective effects of Moringa oleifera seeds in spontaneous hypertensive rats
BACKGROUND Hypertension is characterized by a maintained high blood pressure leading to cardiac complications such as left ventricular hypertrophy and fibrosis and an increased risk of heart failure and myocardial infarction. This study investigated the cardiac effects of oral administration of Moringa oleifera (MOI) seed powder in spontaneous hypertensive rats (SHR).
METHODS SHR received food containing MOI seed powder (750mg/d, 8 weeks) or normal food. In vivo measurement of hemodynamic parameters by telemetry and cardiac structure and function analysis by echocardiography were performed. Histological studies were performed to determine fibrosis and protein expression.
RESULTS MOI treatment did not modify blood pressure in SHR but reduced nocturnal heart rate and improved cardiac diastolic function (reduction of isovolumetric relaxation time and deceleration time of the E wave, increase of ejection volume and cardiac output compared to nontreated SHR). Left ventricular anterior wall thickness, interseptal thickness on diastole, and relative wall thickness were reduced after MOI treatment. Furthermore, we found a significant reduction of fibrosis in the left ventricle of MOI-treated SHR. This antihypertrophic and antifibrotic effect of MOI was associated with increased expression of peroxisome proliferator-activated receptor (PPAR)-α and δ, reduced cardiac triglyceride level, and enhanced plasmatic prostacyclins.
CONCLUSIONS Our data show a beneficial effect of MOI on the cardiac structure and function in SHR associated with an upregulation of PPAR-α and δ signaling. This study thus provides scientific rational support for the empirical use of MOI in the traditional Malagasy medicine against cardiac diseases associated with blood pressure overload
The XXL Survey VIII: MUSE characterisation of intracluster light in a z0.53 cluster of galaxies
Within a cluster, gravitational effects can lead to the removal of stars from
their parent galaxies. Gas hydrodynamical effects can additionally strip gas
and dust from galaxies. The properties of the ICL can therefore help constrain
the physical processes at work in clusters by serving as a fossil record of the
interaction history. The present study is designed to characterise this ICL in
a ~10^14 M_odot and z~0.53 cluster of galaxies from imaging and spectroscopic
points of view. By applying a wavelet-based method to CFHT Megacam and WIRCAM
images, we detect significant quantities of diffuse light. These sources were
then spectroscopically characterised with MUSE. MUSE data were also used to
compute redshifts of 24 cluster galaxies and search for cluster substructures.
An atypically large amount of ICL has been detected in this cluster. Part of
the detected diffuse light has a very weak optical stellar component and
apparently consists mainly of gas emission, while other diffuse light sources
are clearly dominated by old stars. Furthermore, emission lines were detected
in several places of diffuse light. Our spectral analysis shows that this
emission likely originates from low-excitation parameter gas. The stellar
contribution to the ICL is about 2.3x10^9 yrs old even though the ICL is not
currently forming a large number of stars. On the other hand, the contribution
of the gas emission to the ICL in the optical is much greater than the stellar
contribution in some regions, but the gas density is likely too low to form
stars. These observations favour ram pressure stripping, turbulent viscous
stripping, or supernovae winds as the origin of the large amount of
intracluster light. Since the cluster appears not to be in a major merging
phase, we conclude that ram pressure stripping is the most plausible process
that generates the observed ICL sources.Comment: Accepted in A&A, english enhanced, figure location different than in
the A&A version due to different style files, shortened abstrac
The 2-10 keV unabsorbed luminosity function of AGN from the XMM-Newton LSS, CDFS and COSMOS surveys
The XMM-LSS, XMM-COSMOS, and XMM-CDFS surveys are complementary in terms of
sky coverage and depth. Together, they form a clean sample with the least
possible variance in instrument effective areas and PSF. Therefore this is one
of the best samples available to determine the 2-10 keV luminosity function of
AGN and its evolution. The samples and the relevant corrections for
incompleteness are described. A total of 2887 AGN is used to build the LF in
the luminosity interval 10^42-10^46 erg/s, and in the redshift interval
0.001-4. A new method to correct for absorption by considering the probability
distribution for the column density conditioned on the hardness ratio is
presented. The binned luminosity function and its evolution is determined with
a variant of the Page-Carrera method, improved to include corrections for
absorption and to account for the full probability distribution of photometric
redshifts. Parametric models, namely a double power-law with LADE or LDDE
evolution, are explored using Bayesian inference. We introduce the
Watanabe-Akaike information criterion (WAIC) to compare the models and estimate
their predictive power. Our data are best described by the LADE model, as
hinted by the WAIC indicator. We also explore the 15-parameter extended LDDE
model recently proposed by Ueda et al., and find that this extension is not
supported by our data. The strength of our method is that it provides:
un-absorbed non-parametric estimates; credible intervals for luminosity
function parameters; model choice according to which one has more predictive
power for future data.Comment: In press on A&A. The revised version corrects typos and the LF
normalisations in tables 1,2,5 and figs.9-12, which were on an incorrect
scale. Online material available at
http://www.astro.lu.se/~piero/xlf/xlf-paper-tables2.tgz . The software is
available on the author's website
http://www.astro.lu.se/~piero/LFTools/index.html and on github:
https://github.com/piero-ranalli/LFTool
The cosmological analysis of X-ray cluster surveys: I- A new method for interpreting number counts
We present a new method aiming to simplify the cosmological analysis of X-ray
cluster surveys. It is based on purely instrumental observable quantities,
considered in a two-dimensional X-ray colour-magnitude diagram (hardness ratio
versus count-rate). The basic principle is that, even in rather shallow
surveys, substantial information on cluster redshift and temperature is present
in the raw X-ray data and can be statistically extracted; in parallel, such
diagrams can be readily predicted from an ab initio cosmological modeling. We
illustrate the methodology for the case of a 100 deg2 XMM survey having a
sensitivity of ~10^{-14} ergs/s/cm^2 and fit at the same time, the survey
selection function, the cluster evolutionary scaling-relations and the
cosmology; our sole assumption -- driven by the limited size of the sample
considered in the case-study -- is that the local cluster scaling relations are
known. We devote special care to the realistic modeling of the count-rate
measurement uncertainties and evaluate the potential of the method via a Fisher
analysis. In the absence of individual cluster redshifts, the CR-HR method
appears to be much more efficient than the traditional approach based on
cluster counts (i.e. dn/dz, requiring redshifts). In the case where redshifts
are available, our method performs similarly as the traditional mass function
(dn/dM/dz) for the purely cosmological parameters, but better constrains
parameters defining the cluster scaling relations and their evolution. A
further practical advantage of the CR-HR method is its simplicity : this fully
top-down approach totally bypasses the tedious steps consisting in deriving
cluster masses from X-ray temperature measurements.Comment: 18 pages, 15 figures, 3 tables. Accepted for publication in MNRAS
(minor changes with respect to previous version
Redshift-space correlation functions in large galaxy cluster surveys
Large ongoing and upcoming galaxy cluster surveys in the optical, X-ray and
millimetric wavelengths will provide rich samples of galaxy clusters at
unprecedented depths. One key observable for constraining cosmological models
is the correlation function of these objects, measured through their
spectroscopic redshift. We study the redshift-space correlation functions of
clusters of galaxies, averaged over finite redshift intervals, and their
covariance matrices. Expanding as usual the angular anisotropy of the
redshift-space correlation on Legendre polynomials, we consider the
redshift-space distortions of the monopole as well as the next two multipoles,
and 4. Taking into account the Kaiser effect, we developed an
analytical formalism to obtain explicit expressions of all contributions to
these mean correlations and covariance matrices. We include shot-noise and
sample-variance effects as well as Gaussian and non-Gaussian contributions. We
obtain a reasonable agreement with numerical simulations for the mean
correlations and covariance matrices on large scales (Mpc).
Redshift-space distortions amplify the monopole correlation by about ,
depending on the halo mass, but the signal-to-noise ratio remains of the same
order as for the real-space correlation. This distortion will be significant
for surveys such as DES, Erosita, and Euclid, which should also measure the
quadrupole . The third multipole, , may only be marginally
detected by Euclid.Comment: 20 page
The XXL Survey VII: A supercluster of galaxies at z=0.43
The XXL Survey is the largest homogeneous and contiguous survey carried out
with XMM-Newton. Covering an area of 50 square degrees distributed over two
fields, it primarily investigates the large-scale structures of the Universe
using the distribution of galaxy clusters and active galactic nuclei as tracers
of the matter distribution. Given its depth and sky coverage, XXL is
particularly suited to systematically unveiling the clustering of X-ray
clusters and to identifying superstructures in a homogeneous X-ray sample down
to the typical mass scale of a local massive cluster. A friends-of-friends
algorithm in three-dimensional physical space was run to identify large-scale
structures. In this paper we report the discovery of the highest redshift
supercluster of galaxies found in the XXL Survey. We describe the X-ray
properties of the clusters members of the structure and the optical follow-up.
The newly discovered supercluster is composed of six clusters of galaxies at a
median redshift z around 0.43 and distributed across approximately 30 by 15 arc
minutes (10 by 5 Mpc on sky) on the sky. This structure is very compact with
all the clusters residing in one XMM pointing; for this reason this is the
first supercluster discovered with the XXL Survey. Spectroscopic follow-up with
WHT (William Herschel Telescope) and NTT (New Technology Telescope) confirmed a
median redshift of z = 0.43. An estimate of the X-ray mass and luminosity of
this supercluster and of its total gas mass put XLSSC-e at the average mass
range of superclusters; its appearance, with two members of equal size, is
quite unusual with respect to other superclusters and provides a unique view of
the formation process of a massive structure.Comment: A&A, accepted; special XXL issu
The XXL Survey XI: ATCA 2.1 GHz continuum observations
We present 2.1 GHz imaging with the Australia Telescope Compact Array (ATCA)
of a 6.5 deg^2 region within the XXM-Newton XXL South field using a band of
1.1-3.1 GHz. We achieve an angular resolution of 4.7" x 4.2" in the final radio
continuum map with a median rms noise level of 50 uJy/beam. We identify 1389
radio sources in the field with peak S/N >=5 and present the catalogue of
observed parameters. We find that 305 sources are resolved, of which 77 consist
of multiple radio components. These number counts are in agreement with those
found for the COSMOS-VLA 1.4 GHz survey. We derive spectral indices by a
comparison with the Sydney University Molongolo Sky Survey (SUMSS) 843MHz data.
We find an average spectral index of -0.78 and a scatter of 0.28, in line with
expectations. This pilot survey was conducted in preparation for a larger ATCA
program to observe the full 25 deg^2 southern XXL field. When complete, the
survey will provide a unique resource of sensitive, wide-field radio continuum
imaging with complementary X-ray data in the field. This will facilitate
studies of the physical mechanisms of radio-loud and radio-quiet AGNs and
galaxy clusters, and the role they play in galaxy evolution. The source
catalogue is publicly available online via the XXL Master Catalogue browser and
the Centre de Donn\'ees astronomiques de Strasbourg (CDS).Comment: 7 pages, 6 figures. Accepted by A&A 13th October 201
The XXL Survey X: K-band luminosity - weak-lensing mass relation for groups and clusters of galaxies
We present the K-band luminosity-halo mass relation, ,
for a subsample of 20 of the 100 brightest clusters in the XXL Survey observed
with WIRCam at the Canada-France-Hawaii Telescope (CFHT). For the first time,
we have measured this relation via weak-lensing analysis down to . This allows us to investigate whether the slope
of the relation is different for groups and clusters, as seen in other
works. The clusters in our sample span a wide range in mass, , at . The K-band luminosity
scales as with and an
intrinsic scatter of . Combining our
sample with some clusters in the Local Cluster Substructure Survey (LoCuSS)
present in the literature, we obtain a slope of and an
intrinsic scatter of . The flattening in the seen
in previous works is not seen here and might be a result of a bias in the mass
measurement due to assumptions on the dynamical state of the systems. We also
study the richness-mass relation and find that group-sized halos have more
galaxies per unit halo mass than massive clusters. However, the brightest
cluster galaxy (BCG) in low-mass systems contributes a greater fraction to the
total cluster light than BCGs do in massive clusters; the luminosity gap
between the two brightest galaxies is more prominent for group-sized halos.
This result is a natural outcome of the hierarchical growth of structures,
where massive galaxies form and gain mass within low-mass groups and are
ultimately accreted into more massive clusters to become either part of the BCG
or one of the brighter galaxies. [Abridged]Comment: A&A, in pres
Actors' perception on future wood production in a cross-border amazonian region: challenges for a sustainable production.
We conducted a study in a cross-border region of Amazonia to analyze the future role of natural forests in producing wood products. French Guiana and the state of Amapa are sharing similar geographical properties. A predominant area of these two territories are dominated by undisturbed tropical forests. In both regions, over 70% of forest areas is under public ownership. Currently the forestry sector in both regions do not have a key role in local economies, with low legal wood production in French Guiana (75 000 m3) as well as in Amapa (around 120 000 m3). Although in Amapá there is a high level of illegality in the sector (85%). In French Guiana and Amapa, forestry activities might represent an economical opportunity to promote endogenous development. The forest sector, including private and public actors, will face strategic choices to respond to increasing demand in wood supply for the coming decades. Strategic choices, based on strong political decisions, include the volume of wood to be produced locally, type of actors involved (i.e. communities, private companies), type of production (timber vs fuelwood) and origin of wood (plantation vs natural forest). Based on a prospective approach, we identified various scenarios, for each region, to reach the wood supply by 2045. First, we interviewed key actors of the forestry sector to obtain the view from their perspective. Second we selected the key variables to construct the scenarios and validated the resulting scenarios through a discussion with all actors. The scenarios identified in French Guiana had the implementation of tree plantation with local species as alternative to natural forest management, while in Amapa they focused on forest management associated with public policy and social factors. These scenarios are providing a framework of discussions that could help actors to focus on long term and to imagine the likely impact of current policy choices on the socioeconomy and conservation of natural forests.Na publicação consta: Castro Euler, A. M; Guedes, M.; Gazel Yared, J. A.; Doff Sotta, E. IUFRO17-2755
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