19 research outputs found
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 catalogue: X-ray sources and associated optical data. Version I
Following the presentation of the XMM-LSS X-ray source detection package by
Pacaud et al., we provide the source lists for the first 5.5 surveyed square
degrees. The catalogues pertain to the [0.5-2] and [2-10] keV bands and contain
in total 3385 point-like or extended sources above a detection likelihood of 15
in either band. The agreement with deep logN-logS is excellent. The main
parameters considered are position, countrate, source extent with associated
likelihood values. A set of additional quantities such as astrometric
corrections and fluxes are further calculated while errors on the position and
countrate are deduced from simulations. We describe the construction of the
band-merged catalogue allowing rapid sub-sample selection and easy
cross-correlation with external multi-wavelength catalogues. A small optical
CFHTLS multi-band subset of objects is associated wich each source along with
an X-ray/optical overlay. We make the full X-ray images available in FITS
format. The data are available at CDS and, in a more extended form, at the
Milan XMM-LSS database.Comment: 13 pages, 7 figures and 11 tables (fig. 1 and 6 are enclosed in
reduced resolution), MNRAS Latex, accepted by MNRA
I. Flux and color variations of the quadruply imaged quasar HE 0435-1223
aims: We present VRi photometric observations of the quadruply imaged quasar
HE 0435-1223, carried out with the Danish 1.54m telescope at the La Silla
Observatory. Our aim was to monitor and study the magnitudes and colors of each
lensed component as a function of time. methods: We monitored the object during
two seasons (2008 and 2009) in the VRi spectral bands, and reduced the data
with two independent techniques: difference imaging and PSF (Point Spread
Function) fitting.results: Between these two seasons, our results show an
evident decrease in flux by ~0.2-0.4 magnitudes of the four lensed components
in the three filters. We also found a significant increase (~0.05-0.015) in
their V-R and R-i color indices. conclusions: These flux and color variations
are very likely caused by intrinsic variations of the quasar between the
observed epochs. Microlensing effects probably also affect the brightest "A"
lensed component.Comment: 10 pages, 8 figure
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
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
The XMM large scale structure survey: optical vs. X-ray classifications of active galactic nuclei and the unified scheme
Our goal is to characterize AGN populations by comparing their X-ray and
optical classifications. We present a sample of 99 spectroscopically identified
X-ray point sources in the XMM-LSS survey which are significantly detected in
the [2-10] keV band, and with more than 80 counts. We performed an X-ray
spectral analysis for all of these 99 X-ray sources. Introducing the fourfold
point correlation coefficient, we find only a mild correlation between the
X-ray and the optical classifications, as up to 30% of the sources have
differing X-ray and optical classifications: on one hand, 10% of the type 1
sources present broad emission lines in their optical spectra and strong
absorption in the X-rays. These objects are highly luminous AGN lying at high
redshift and thus dilution effects are totally ruled out, their discrepant
nature being an intrinsic property. Their X-ray luminosities and redshifts
distributions are consistent with those of the unabsorbed X-ray sources with
broad emission lines. On the other hand, 25/32 are moderate luminosity AGN,
which are both unabsorbed in the X-rays and only present narrow emission lines
in their optical spectra. The majority of them have an optical spectrum which
is representative of the host galaxy. We finally infer that dilution of the AGN
by the host galaxy seems to account for their nature. 5/25 have been defined as
Seyfert 2. In conclusion, most of these 32 discrepant cases can be accounted
for by the standard AGN unified scheme, as its predictions are not met for only
12% of the 99 X-ray sources. ABRIDGEDComment: 25 pages, 19 figures, Accepted for publication in A&
Redalyc.NEW WEB TECHNOLOGIES FOR ASTRONOMY
RESUMEN Gracias a las nuevas capacidades de HTML5, y las grandes mejoras del lenguaje JavaScript es posible diseñar interfaces web muy complejas e interactivas. Además, los servidores que eran una vez monolíticos y orientados a servir archivos, están evolucionando a aplicaciones de servidor fácilmente programables, capaces de lidiar con interacciones complejas gracias a la nueva generación de navegadores. Nosotros creemos que la comunidad de astrónomos profesionales y aficionados entera puede beneficiarse del potencial de estas nuevas tecnologías. Nuevas interfaces web pueden ser diseñadas para proveer al usuario con herramientas mucho más intuitivas e interactivas. Acceder a archivos de datos astronómicos, controlar y monitorear observatorios y en particular telescopios robóticos, supervisar pipelines de reducción de datos, son todas capacidades que pueden ser implementadas en una aplicación web JavaScript. Describimos el paquete Sadira que estamos implementando exactamente con este propósito. ABSTRACT Thanks to the new HTML5 capabilities and the huge improvements of the JavaScript language, it is now possible to design very complex and interactive web user interfaces. On top of that, the once monolithic and file-server oriented web servers are evolving into easily programmable server applications capable to cope with the complex interactions made possible by the new generation of browsers. We believe that the whole community of amateur and professionals astronomers can benefit from the potential of these new technologies. New web interfaces can be designed to provide the user with a large deal of much more intuitive and interactive tools. Accessing astronomical data archives, schedule, control and monitor observatories, and in particular robotic telescopes, supervising data reduction pipelines, all are capabilities that can now be implemented in a JavaScript web application. In this paper we describe the Sadira package we are implementing exactly to this aim