100 research outputs found
The cosmological analysis of X-ray cluster surveys: II- Application of the CR-HR method to the XMM archive
We have processed 2774 high-galactic observations from the XMM archive (as of
May 2010) and extracted a serendipitous catalogue of some 850 clusters of
galaxies based on purely X-ray criteria, following the methodology developed
for the XMM-LSS survey. Restricting the sample to the highest signal-to-noise
objects (347 clusters), we perform a cosmological analysis using the X-ray
information only. The analysis consists in the modelling of the observed
colour-magnitude (CR-HR) diagram constructed from cluster instrumental
count-rates measured in the [0.5-2], [1-2] and [0.5-1] keV bands. A MCMC
procedure simultaneously fits the cosmological parameters, the evolution of the
cluster scaling laws and the selection effects. Our results are consistent with
the sigma_8 and Omega_m values obtained by WMAP-5 and point toward a negative
evolution of the cluster scaling relations with respect to the self-similar
expectation. We are further able to constrain the cluster fractional radius
xc0=r_c/r500c, to xc0=0.24 +/- 0.04. This study stresses again the critical
role of selection effects in deriving cluster scaling relations, even in the
local universe. Finally, we show that CR-HR method applied to the eRosita
all-sky survey - provided that cluster photometric redshifts are available -
will enable the determination of the equation of state of the dark energy at
the level of the DETF stage IV predictions; simultaneously, the evolution of
the cluster scaling-relations will be unambiguously determined. The XMM CLuster
Archive Super Survey (XCLASS) serendipitous cluster catalogue is available
online at: http://xmm-lss.in2p3.fr:8080/l4sdb/.Comment: 26 pages, 24 figures, 9 tables. Accepted for publication in MNRAS
(minor changes with respect to submitted version). The corresponding galaxy
cluster catalogue is available at http://xmm-lss.in2p3.fr:8080/l4sdb
The XMM-LSS Survey: A well controlled X-ray cluster sample over the D1 CFHTLS area
We present the XMM-LSS cluster catalogue corresponding to the CFHTLS D1 area.
The list contains 13 spectroscopically confirmed, X-ray selected galaxy
clusters over 0.8 deg2 to a redshift of unity and so constitutes the highest
density sample of clusters to date. Cluster X-ray bolometric luminosities range
from 0.03 to 5x10^{44} erg/s. In this study, we describe our catalogue
construction procedure: from the detection of X-ray cluster candidates to the
compilation of a spectroscopically confirmed cluster sample with an explicit
selection function. The procedure further provides basic X-ray products such as
cluster temperature, flux and luminosity. We detected slightly more clusters
with a (0.5-2.0 keV) X-ray fluxes of >2x10^{-14} erg/s/cm^{-2} than we expected
based on expectations from deep ROSAT surveys. We also present the
Luminosity-Temperature relation for our 9 brightest objects possessing a
reliable temperature determination. The slope is in good agreement with the
local relation, yet compatible with a luminosity enhancement for the 0.15 < z<
0.35 objects having 1 < T < 2 keV, a population that the XMM-LSS is identifying
systematically for the first time. The present study permits the compilation of
cluster samples from XMM images whose selection biases are understood. This
allows, in addition to studies of large-scale structure, the systematic
investigation of cluster scaling law evolution, especially for low mass X-ray
groups which constitute the bulk of our observed cluster population. All
cluster ancillary data (images, profiles, spectra) are made available in
electronic form via the XMM-LSS cluster database.Comment: 12 pages 5 figures, MNRAS accepted. The paper with full resolution
cluster images is available at
http://vela.astro.ulg.ac.be/themes/spatial/xmm/LSS/rel_pub_e.htm
The XMM-LSS survey. Survey design and first results
We have designed a medium deep large area X-ray survey with XMM - the XMM
Large Scale Structure survey, XMM-LSS - with the scope of extending the
cosmological tests attempted using ROSAT cluster samples to two redshift bins
between 0<z<1 while maintaining the precision of earlier studies. Two main
goals have constrained the survey design: the evolutionary study of the
cluster-cluster correlation function and of the cluster number density. The
results are promising and, so far, in accordance with our predictions as to the
survey sensitivity and cluster number density. The feasibility of the programme
is demonstrated and further X-ray coverage is awaited in order to proceed with
a truly significant statistical analysis. (Abridged)Comment: Published in Journal of Cosmology and Astroparticle Physic
The XMM-LSS survey: the Class 1 cluster sample over the initial 5 square degrees and its cosmological modelling
We present a sample of 29 galaxy clusters from the XMM-LSS survey over an
area of some 5deg2 out to a redshift of z=1.05. The sample clusters, which
represent about half of the X-ray clusters identified in the region, follow
well defined X-ray selection criteria and are all spectroscopically confirmed.
For all clusters, we provide X-ray luminosities and temperatures as well as
masses. The cluster distribution peaks around z=0.3 and T =1.5 keV, half of the
objects being groups with a temperature below 2 keV. Our L-T(z) relation points
toward self-similar evolution, but does not exclude other physically plausible
models. Assuming that cluster scaling laws follow self-similar evolution, our
number density estimates up to z=1 are compatible with the predictions of the
concordance cosmology and with the findings of previous ROSAT surveys. Our well
monitored selection function allowed us to demonstrate that the inclusion of
selection effects is essential for the correct determination of the evolution
of the L-T relation, which may explain the contradictory results from previous
studies. Extensive simulations show that extending the survey area to 10deg2
has the potential to exclude the non-evolution hypothesis, but that constraints
on more refined ICM models will probably be limited by the large intrinsic
dispersion of the L-T relation. We further demonstrate that increasing the
dispersion in the scaling laws increases the number of detectable clusters,
hence generating further degeneracy [in addition to sigma8, Omega_m, L(M,z) and
T(M,z)] in the cosmological interpretation of the cluster number counts. We
provide useful empirical formulae for the cluster mass-flux and mass-count-rate
relations as well as a comparison between the XMM-LSS mass sensitivity and that
of forthcoming SZ surveys.Comment: Accepted for publication by MNRAS. Full resolution images as well as
additional cluster data are available through a dedicated database at
http://l3sdb.in2p3.fr:8080/l3sdb
XMM-LSS discovery of a z=1.22 galaxy cluster
We present details of the discovery of XLSSJ022303.0-043622, a z=1.2 cluster
of galaxies. This cluster was identified from its X-ray properties and selected
as a z>1 candidate from its optical/near-IR characteristics in the XMM
Large-Scale Structure Survey (XMM-LSS). It is the most distant system
discovered in the survey to date. We present ground-based optical and near IR
observations of the system carried out as part of the XMM-LSS survey. The
cluster has a bolometric X-ray luminosity of 1.1 +/- 0.7 x 10^44 erg/s, fainter
than most other known z>1 X-ray selected clusters. In the optical it has a
remarkably compact core, with at least a dozen galaxies inside a 125 kpc radius
circle centred on the X-ray position. Most of the galaxies within the core, and
those spectroscopically confirmed to be cluster members, have stellar masses
similar to those of massive cluster galaxies at low redshift. They have colours
comparable to those of galaxies in other z>1 clusters, consistent with showing
little sign of strong ongoing star formation. The bulk of the star formation
within the galaxies appears to have ceased at least 1.5 Gyr before the observed
epoch. Our results are consistent with massive cluster galaxies forming at z>1
and passively evolving thereafter. We also show that the system is
straightforwardly identified in Spitzer/IRAC 3.6 and 4.5 micron data obtained
by the SWIRE survey emphasising the power and utility of joint XMM and Spitzer
searches for the most distant clusters.Comment: 8 pages, 6 figures, MNRAS accepte
The XMM-LSS cluster sample and its cosmological applications. Prospects for the XMM next decade
The well defined selection function of the XMM-LSS survey enables a
simultaneous modelling of the observed cluster number counts and of the
evolution of the L-T relation. We present results pertaining to the first 5
deg2 for a well controlled sample comprising 30 objects: they are compatible
with the WMAP3 parameter set along with cluster self-similar evolution.
Extending such a survey to 200 deg2 would (1) allow discriminating between the
major scenarios of the cluster L-T evolution and (2) provide a unique
self-sufficient determination of sigma8 and Gamma with an accuracy of ~ 5% and
10% respectively, when adding mass information from weak lensing and S-Z
observations.Comment: Proceedings of the "XMM-Newton: the next decade", to appear in
Astronomische Nachrichte
Large genomic rearrangements in the CFTR gene contribute to CBAVD
<p>Abstract</p> <p>Background</p> <p>By performing extensive scanning of whole coding and flanking sequences of the <it>CFTR (Cystic Fibrosis Transmembrane Conductance Regulator</it>) gene, we had previously identified point mutations in 167 out of 182 (91.7%) males with isolated congenital bilateral absence of the vas deferens (CBAVD). Conventional PCR-based methods of mutation analysis do not detect gross DNA lesions. In this study, we looked for large rearrangements within the whole <it>CFTR </it>locus in the 32 CBAVD patients with only one or no mutation.</p> <p>Methods</p> <p>We developed a semi-quantitative fluorescent PCR assay (SQF-PCR), which relies on the comparison of the fluorescent profiles of multiplex PCR fragments obtained from different DNA samples. We confirmed the gross alterations by junction fragment amplification and identified their breakpoints by direct sequencing.</p> <p>Results</p> <p>We detected two large genomic heterozygous deletions, one encompassing exon 2 (c.54-5811_c.164+2186del8108ins182) [or <it>CFTRdele2</it>], the other removing exons 22 to 24 (c.3964-3890_c.4443+3143del9454ins5) [or <it>CFTRdele 22_24</it>], in two males carrying a typical CBAVD mutation on the other parental <it>CFTR </it>allele. We present the first bioinformatic tool for exon phasing of the <it>CFTR </it>gene, which can help to rename the exons and the nomenclature of small mutations according to international recommendations and to predict the consequence of large rearrangements on the open reading frame.</p> <p>Conclusion</p> <p>Identification of large rearrangements further expands the <it>CFTR </it>mutational spectrum in CBAVD and should now be systematically investigated. We have designed a simple test to specifically detect the presence or absence of the two rearrangements identified in this study.</p
A chemical survey of exoplanets with ARIEL
Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio
Cluster Lenses
Clusters of galaxies are the most recently assembled, massive, bound
structures in the Universe. As predicted by General Relativity, given their
masses, clusters strongly deform space-time in their vicinity. Clusters act as
some of the most powerful gravitational lenses in the Universe. Light rays
traversing through clusters from distant sources are hence deflected, and the
resulting images of these distant objects therefore appear distorted and
magnified. Lensing by clusters occurs in two regimes, each with unique
observational signatures. The strong lensing regime is characterized by effects
readily seen by eye, namely, the production of giant arcs, multiple-images, and
arclets. The weak lensing regime is characterized by small deformations in the
shapes of background galaxies only detectable statistically. Cluster lenses
have been exploited successfully to address several important current questions
in cosmology: (i) the study of the lens(es) - understanding cluster mass
distributions and issues pertaining to cluster formation and evolution, as well
as constraining the nature of dark matter; (ii) the study of the lensed objects
- probing the properties of the background lensed galaxy population - which is
statistically at higher redshifts and of lower intrinsic luminosity thus
enabling the probing of galaxy formation at the earliest times right up to the
Dark Ages; and (iii) the study of the geometry of the Universe - as the
strength of lensing depends on the ratios of angular diameter distances between
the lens, source and observer, lens deflections are sensitive to the value of
cosmological parameters and offer a powerful geometric tool to probe Dark
Energy. In this review, we present the basics of cluster lensing and provide a
current status report of the field.Comment: About 120 pages - Published in Open Access at:
http://www.springerlink.com/content/j183018170485723/ . arXiv admin note:
text overlap with arXiv:astro-ph/0504478 and arXiv:1003.3674 by other author
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