159 research outputs found
The XXL Survey: XII. Optical spectroscopy of X-ray-selected clusters and the frequency of AGN in superclusters
This article belongs to the first series of XXL publications. It presents
multifibre spectroscopic observations of three 0.55 sq.deg. fields in the XXL
Survey, which were selected on the basis of their high density of
X-ray-detected clusters. The observations were obtained with the
AutoFib2+WYFFOS (AF2) wide-field fibre spectrograph mounted on the 4.2m William
Herschel Telescope. The paper first describes the scientific rationale, the
preparation, the data reduction, and the results of the observations, and then
presents a study of active galactic nuclei (AGN) within three superclusters. We
obtained redshifts for 455 galaxies in total, 56 of which are counterparts of
X-ray point-like sources. We were able to determine the redshift of the merging
supercluster XLSSC-e, which consists of six individual clusters at z~0.43, and
we confirmed the redshift of supercluster XLSSC-d at z~0.3. More importantly,
we discovered a new supercluster, XLSSC-f, that comprises three galaxy clusters
also at z~0.3. We find a significant 2D overdensity of X-ray point-like sources
only around the supercluster XLSSC-f. This result is also supported by the
spatial (3D) analysis of XLSSC-f, where we find four AGN with compatible
spectroscopic redshifts and possibly one more with compatible photometric
redshift. In addition, we find two AGN (3D analysis) at the redshift of
XLSSC-e, but no AGN in XLSSC-d. Comparing these findings with the optical
galaxy overdensity we conclude that the total number of AGN in the area of the
three superclusters significantly exceeds the field expectations. The
difference in the AGN frequency between the three superclusters cannot be
explained by the present study because of small number statistics. Further
analysis of a larger number of superclusters within the 50 sq. deg. of the XXL
is needed before any conclusions on the effect of the supercluster environment
on AGN can be reached.Comment: 11 pages, published by A&
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 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
Non-parametric modeling of the intra-cluster gas using APEX-SZ bolometer imaging data
We demonstrate the usability of mm-wavelength imaging data obtained from the
APEX-SZ bolometer array to derive the radial temperature profile of the hot
intra-cluster gas out to radius r_500 and beyond. The goal is to study the
physical properties of the intra-cluster gas by using a non-parametric
de-projection method that is, aside from the assumption of spherical symmetry,
free from modeling bias. We use publicly available X-ray imaging data from the
XMM-Newton observatory and our Sunyaev-Zel'dovich Effect (SZE) imaging data
from the APEX-SZ experiment at 150 GHz to de-project the density and
temperature profiles for the relaxed cluster Abell 2204. We derive the gas
density, temperature and entropy profiles assuming spherical symmetry, and
obtain the total mass profile under the assumption of hydrostatic equilibrium.
For comparison with X-ray spectroscopic temperature models, a re-analysis of
the recent Chandra observation is done with the latest calibration updates.
Using the non-parametric modeling we demonstrate a decrease of gas temperature
in the cluster outskirts, and also measure the gas entropy profile. These
results are obtained for the first time independently of X-ray spectroscopy,
using SZE and X-ray imaging data. The contribution of the SZE systematic
uncertainties in measuring T_e at large radii is shown to be small compared to
the Chandra systematic spectroscopic errors. The upper limit on M_200 derived
from the non-parametric method is consistent with the NFW model prediction from
weak lensing analysis.Comment: Replaced with the published version; A&A 519, A29 (2010
The eROSITA Final Equatorial-Depth Survey (eFEDS): X-ray properties of Subaru optically-selected clusters
We present the results of a systematic X-ray analysis of optically rich
galaxy clusters detected by the Subaru HSC survey in the eROSITA eFEDS field.
Through a joint analysis of SRG/eROSITA and Subaru/HSC surveys, we aim to study
the dynamical status of the optically selected clusters and derive the cluster
scaling relations. The sample consists of 43 optically selected galaxy clusters
with a richness in . We systematically analyzed the X-ray
images and spectra using the eROSITA data. We identified the BCG using the
optical and far-infrared databases. We evaluated the cluster's dynamical status
by measuring the offset between the X-ray peak and BCG position, the gas
concentration, and the number of galaxy-density peaks. We studied the
luminosity-temperature and mass-luminosity relations based on eROSITA X-ray
spectra and HSC weak-lensing data analyses. Based on the these measurements,
the fraction of relaxed clusters is %, which is smaller than that of
the X-ray-selected cluster samples. After correcting for a selection bias due
to the richness cut, we obtained a shallow slope of , which is
consistent with the predictions of the self-similar model and the baseline
model incorporating a mass-concentration relation. The slope of
agrees with the above theoretical models and that of the
shear-selected clusters in the eFEDs field. Our analysis of high-richness
optical clusters yields a small fraction of relaxed clusters and a shallow
slope for the luminosity-temperature relation. This suggests that the average
X-ray properties of the optical clusters are likely to be different from those
observed in the X-ray samples. Thus, the joint eROSITA and HSC observations are
a powerful tool in extending the analysis to a larger sample and understanding
the selection effect with a view to establish cluster scaling relations.Comment: 12 pages, 4 figures, A&A accepted, minor correctio
Multiwavelength characterization of faint ultra steep spectrum radio sources: a search for high-redshift radio galaxies
Context. Ultra steep spectrum (USS) radio sources are one of the efficient tracers of powerful high-z radio galaxies (HzRGs). In contrast to searches for powerful HzRGs from radio surveys of moderate depths, fainter USS samples derived from deeper radio surveys can be useful in finding HzRGs at even higher redshifts and in unveiling a population of obscured weaker radio-loud AGN at moderate redshifts.
Aims. Using our 325 MHz GMRT observations (5σ ∼ 800 μJy) and 1.4 GHz VLA observations (5σ ∼ 80−100 μJy) available in two subfields (VLA-VIMOS VLT Deep Survey (VLA-VVDS) and Subaru X-ray Deep Field (SXDF)) of the XMM-LSS field, we derive a large sample of 160 faint USS radio sources and characterize their nature.
Methods. The optical and IR counterparts of our USS sample sources are searched using existing deep surveys, at respective wavelengths. We attempt to unveil the nature of our faint USS sources using diagnostic techniques based on mid-IR colors, flux ratios of radio to mid-IR, and radio luminosities. Results. Redshift estimates are available for 86/116 (∼74%) USS sources in the VLA-VVDS field and for 39/44 (∼87%) USS sources in the SXDF fields with median values (zmedian) ∼1.18 and ∼1.57, respectively, which are higher than estimates for non-USS radio sources (zmedian non−USS ∼ 0.99 and ∼0.96), in the two subfields. The MIR color–color diagnostic and radio luminosities are consistent with most of our USS sample sources at higher redshifts (z > 0.5) being AGN. The flux ratio of radio to mid-IR (S 1.4 GHz/S 3.6 μm) versus redshift diagnostic plot suggests that more than half of our USS sample sources distributed over z ∼ 0.5 to 3.8 are likely to be hosted in obscured environments. A significant fraction (∼26% in the VLA-VVDS and ∼13% in the SXDF) of our USS sources without redshift estimates mostly remain unidentified in the existing optical, IR surveys, and exhibit high radio to mid-IR flux ratio limits similar to HzRGs, and so, can be considered as potential HzRG candidates.
Conclusions. Our study shows that the criterion of ultra steep spectral index remains a reasonably efficient method to select high-z sources even at sub-mJy flux densities. In addition to powerful HzRG candidates, our faint USS sample also contains populations of weaker radio-loud AGNs potentially hosted in obscured environments
The XXL Survey IV. Mass-temperature relation of the bright cluster sample
The XXL survey is the largest survey carried out by XMM-Newton. Covering an area of 50deg, the survey contains galaxy clusters out to a redshift 2 and to an X-ray flux limit of . This paper is part of the first release of XXL results focussed on the bright cluster sample. We investigate the scaling relation between weak-lensing mass and X-ray temperature for the brightest clusters in XXL. The scaling relation is used to estimate the mass of all 100 clusters in XXL-100-GC. Based on a subsample of 38 objects that lie within the intersection of the northern XXL field and the publicly available CFHTLenS catalog, we derive the of each system with careful considerations of the systematics. The clusters lie at and span a range of . We combine our sample with 58 clusters from the literature, increasing the range out to 10keV. To date, this is the largest sample of clusters with measurements that has been used to study the mass-temperature relation. The fit () to the XXL clusters returns a slope and intrinsic scatter ; the scatter is dominated by disturbed clusters. The fit to the combined sample of 96 clusters is in tension with self-similarity, and . Overall our results demonstrate the feasibility of ground-based weak-lensing scaling relation studies down to cool systems of temperature and highlight that the current data and samples are a limit to our statistical precision. As such we are unable to determine whether the validity of hydrostatic equilibrium is a function of halo mass. An enlarged sample of cool systems, deeper weak-lensing data, and robust modelling of the selection function will help to explore these issues further
The Hot and Energetic Universe: The evolution of galaxy groups and clusters
Major astrophysical questions related to the formation and evolution of
structures, and more specifically of galaxy groups and clusters, will still be
open in the coming decade and beyond: what is the interplay of galaxy,
supermassive black hole, and intergalactic gas evolution in the most massive
objects in the Universe - galaxy groups and clusters? What are the processes
driving the evolution of chemical enrichment of the hot diffuse gas in
large-scale structures? How and when did the first galaxy groups in the
Universe, massive enough to bind more than 10^7 K gas, form? Focussing on the
period when groups and clusters assembled (0.5<z<2.5), we show that, due to the
continuum and line emission of this hot intergalactic gas at X-ray wavelengths,
Athena+, combining high sensitivity with excellent spectral and spatial
resolution, will deliver breakthrough observations in view of the
aforementioned issues. Indeed, the physical and chemical properties of the hot
intra-cluster gas, and their evolution across time, are a key to understand the
co-evolution of galaxy and supermassive black hole within their environments.Comment: Supporting paper for the science theme The Hot and Energetic Universe
to be implemented by the Athena+ X-ray observatory
(http://www.the-athena-x-ray-observatory.eu). 10 pages, 4 figure
Cilta-cel or Standard Care in Lenalidomide-Refractory Multiple Myeloma
Background Ciltacabtagene autoleucel (cilta-cel), a B-cell maturation antigen (BCMA)-directed CAR T-cell therapy, is effective in heavily pretreated patients with relapsed or refractory multiple myeloma. We investigated cilta-cel in earlier treatment lines in patients with lenalidomide-refractory disease. Methods In this phase 3, randomized, open-label trial, we assigned patients with lenalidomide-refractory multiple myeloma to receive cilta-cel or the physician's choice of effective standard care. All the patients had received one to three previous lines of treatment. The primary outcome was progression-free survival. Results A total of 419 patients underwent randomization (208 to receive cilta-cel and 211 to receive standard care). At a median follow-up of 15.9 months (range, 0.1 to 27.3), the median progression-free survival was not reached in the cilta-cel group and was 11.8 months in the standard-care group (hazard ratio, 0.26; 95% confidence interval [CI], 0.18 to 0.38; P<0.001). Progression-free survival at 12 months was 75.9% (95% CI, 69.4 to 81.1) in the cilta-cel group and 48.6% (95% CI, 41.5 to 55.3) in the standard-care group. More patients in the cilta-cel group than in the standard-care group had an overall response (84.6% vs. 67.3%), a complete response or better (73.1% vs. 21.8%), and an absence of minimal residual disease (60.6% vs. 15.6%). Death from any cause was reported in 39 patients and 46 patients, respectively (hazard ratio, 0.78; 95% CI, 0.5 to 1.2). Most patients reported grade 3 or 4 adverse events during treatment. Among the 176 patients who received cilta-cel in the as-treated population, 134 (76.1%) had cytokine release syndrome (grade 3 or 4, 1.1%; no grade 5), 8 (4.5%) had immune effector cell-associated neurotoxicity syndrome (all grade 1 or 2), 1 had movement and neurocognitive symptoms (grade 1), 16 (9.1%) had cranial nerve palsy (grade 2, 8.0%; grade 3, 1.1%), and 5 (2.8%) had CAR-T-related peripheral neuropathy (grade 1 or 2, 2.3%; grade 3, 0.6%). Conclusions A single cilta-cel infusion resulted in a lower risk of disease progression or death than standard care in lenalidomide-refractory patients with multiple myeloma who had received one to three previous therapies. (Funded by Janssen and Legend Biotech; CARTITUDE-4 ClinicalTrials.gov number, NCT04181827.
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