The growth of brightest cluster galaxies (BCGs) is closely related to the properties of their host cluster. We present evidence for dry mergers as the dominant source of BCG mass growth at z ≲ 1 in ...the XXL 100 brightest cluster sample. We use the global red sequence, Hα emission and mean star formation history to show that BCGs in the sample possess star formation levels comparable to field ellipticals of similar stellar mass and redshift. XXL 100 brightest clusters are less massive on average than those in other X-ray selected samples such as LoCuSS or HIFLUGCS. Few clusters in the sample display high central gas concentration, rendering inefficient the growth of BCGs via star formation resulting from the accretion of cool gas. Using measures of the relaxation state of their host clusters, we show that BCGs grow as relaxation proceeds. We find that the BCG stellar mass corresponds to a relatively constant fraction 1 per cent of the total cluster mass in relaxed systems. We also show that, following a cluster scale merger event, the BCG stellar mass lags behind the expected value from the Mcluster–MBCG relation but subsequently accretes stellar mass via dry mergers as the BCG and cluster evolve towards a relaxed state.
Euclid preparation Adam, R.; Vannier, M.; Maurogordato, S. ...
Astronomy and astrophysics (Berlin),
07/2019, Letnik:
627
Journal Article
Recenzirano
Odprti dostop
Galaxy cluster counts in bins of mass and redshift have been shown to be a competitive probe to test cosmological models. This method requires an efficient blind detection of clusters from surveys ...with a well-known selection function and robust mass estimates, which is particularly challenging at high redshift. The
Euclid
wide survey will cover 15 000 deg
2
of the sky, avoiding contamination by light from our Galaxy and our solar system in the optical and near-infrared bands, down to magnitude 24 in the
H
-band. The resulting data will make it possible to detect a large number of galaxy clusters spanning a wide-range of masses up to redshift ∼2 and possibly higher. This paper presents the final results of the
Euclid
Cluster Finder Challenge (CFC), fourth in a series of similar challenges. The objective of these challenges was to select the cluster detection algorithms that best meet the requirements of the
Euclid
mission. The final CFC included six independent detection algorithms, based on different techniques, such as photometric redshift tomography, optimal filtering, hierarchical approach, wavelet and friend-of-friends algorithms. These algorithms were blindly applied to a mock galaxy catalog with representative
Euclid
-like properties. The relative performance of the algorithms was assessed by matching the resulting detections to known clusters in the simulations down to masses of
M
200
∼ 10
13.25
M
⊙
. Several matching procedures were tested, thus making it possible to estimate the associated systematic effects on completeness to < 3%. All the tested algorithms are very competitive in terms of performance, with three of them reaching > 80% completeness for a mean purity of 80% down to masses of 10
14
M
⊙
and up to redshift
z
= 2. Based on these results, two algorithms were selected to be implemented in the
Euclid
pipeline, the Adaptive Matched Identifier of Clustered Objects (AMICO) code, based on matched filtering, and the PZWav code, based on an adaptive wavelet approach.
We have processed 2774 high galactic observations from the XMM archive (as of 2010 May) and extracted a serendipitous catalogue of some 850 clusters of galaxies based on purely X-ray criteria, ...following the methodology developed for the XMM-Large-Scale Survey. Restricting the sample to the highest signal-to-noise ratio objects (347 clusters), we perform a cosmological analysis using only the X-ray information. The analysis consists in the modelling of the observed colour-magnitude count rate and hardness ratio (CR-HR) diagram constructed from cluster instrumental count rates measured in the 0.5-2, 1-2 and 0.5-1 keV bands. A Monte Carlo Markov chain procedure simultaneously fits the cosmological parameters, the evolution of the cluster scaling laws and the selection effects.
Our results are consistent with the σ8 and Ωm values obtained by the 5-year Wilkinson Microwave Anisotropy Probe (WMAP5) and point towards 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 x
c,0=r
c/R
500c to x
c, 0= 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 the 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 Dark Energy Task Force (DETF) stage IV predictions; simultaneously, the evolution of the cluster scaling relations will be unambiguously determined.
The XMM CLuster Archive Super Survey (X-CLASS) serendipitous cluster catalogue is available online at http://xmm-lss.in2p3.fr:8080/l4sdb/.
Aims.
Our goal is to better understand the origin and the star-formation history of regions NGC 6334 and NGC 6357. We focus our study on the kinematics of young stars (young stellar objects and OB ...stars) in both regions mainly on the basis of the
Gaia
DR2 data.
Methods.
For both regions, we compiled catalogs of OB stars and young stellar objects from the literature and complemented them using VPHAS+ DR2 and
Spitzer
IRAC/GLIMPSE photometry catalogues. We applied a cross-match with the
Gaia
DR2 catalog to obtain information on the parallax and transverse motion.
Results.
We confirm that NGC 6334 and NGC 6357 are in the far side of the Saggitarius-Carina arm at a distance of 1.76 kpc. For NGC 6357, OB stars show strong clustering and ordered star motion with Vlon ∼–10.7 km s
−1
and Vlat ∼3.7 km s
−1
, whereas for NGC 6334, no significant systemic motion was observed. The OB stars motions and distribution in NGC 6334 suggest that it should be classified as an association. Ten runaway candidates may be related to NGC 6357 and two to NGC 6334, respectively. The spatial distributions of the runaway candidates in and around NGC 6357 favor a dynamical (and early) ejection during the cluster(s) formation. Because such stars are likely to be ejected during a cluster’s formation, the fact that not as many such stars are observed towards NGC 6334 suggests different formation conditions than have been assumed for NGC 6357.
Context. The Ophiuchus cluster, at a redshift z = 0.0296, is known from X-rays to be one of the most massive nearby clusters, but its optical properties have not been investigated in detail because ...of its very low Galactic latitude. Aims. We discuss the optical properties of the galaxies in the Ophiuchus cluster, in particular, with the aim of understanding its dynamical properties better. Methods. We have obtained deep optical imaging in several bands with various telescopes, and applied a sophisticated method to model and subtract the contributions of stars to measure galaxy magnitudes as accurately as possible. The colour−magnitude relations obtained show that there are hardly any blue galaxies in Ophiuchus (at least brighter than r′ ≤ 19.5), and this is confirmed by the fact that we only detect two galaxies in Hα. We also obtained a number of spectra with ESO-FORS2, which we combined with previously available redshifts. Altogether, we have 152 galaxies with spectroscopic redshifts in the 0.02 ≤ z ≤ 0.04 range, and 89 galaxies with both a redshift within the cluster redshift range and a measured r′ band magnitude (limited to the Megacam 1 × 1 deg2 field). Results. A complete dynamical analysis based on the galaxy redshifts available shows that the overall cluster is relaxed and has a mass of 1.1 × 1015 M⊙. The Sernal-Gerbal method detects a main structure and a much smaller substructure, which are not separated in projection. Conclusions. From its dynamical properties derived from optical data, the Ophiuchus cluster seems overall to be a relaxed structure, or at most a minor merger, though in X-rays the central region (radius ~ 150 kpc) may show evidence for merging effects.
Summary
No published reports on the occurrence of Mendelson's syndrome (pneumonitis caused by aspiration during anaesthesia) in horses were found in the literature. Although the peculiar anatomy of ...the equine stomach makes horses less prone than other species to regurgitate, gastric reflux may still occur in horses with colic under certain circumstances. The colic horses in this report had in common stomach impaction, abdominal distention and preanaesthetic placement of a nasogastric tube, which was not withdrawn prior to induction. In both cases, a significant volume of gastric reflux was noted pouring from the endotracheal tube during general anaesthesia for exploratory laparotomy. It was hypothesised that the cause of gastric reflux was the combination of increased intra‐abdominal pressure and patency of the cardia, and that inhalation of gastric content occurred at induction, before tracheal intubation. Treatment, which failed to improve oxygenation, consisted of repositioning of the horses to facilitate passive drainage of gastric content from the airways, active suction through the endotracheal tubes, ventilation strategies, improvement of haemodynamics to increase the pulmonary perfusion, and administration of bronchodilators. One horse was subjected to euthanasia owing to poor prognosis. Aspiration pneumonitis should be regarded as a life‐threatening, although rare, perianaesthetic complication in equine colic cases. Patency of the cardia and increased intra‐abdominal pressure are possible predisposing factors. Partial or even total withdrawal of the nasogastric tube prior to anaesthetic induction and tracheal intubation performed with the horse positioned in sternal recumbency may be undertaken as preventive measures in patients at high risk of developing Mendelson's syndrome.
Context.
Large numbers of deep optical images will be available in the near future, allowing statistically significant studies of low surface brightness structures such as intracluster light (ICL) in ...galaxy clusters. The detection of these structures requires efficient algorithms dedicated to this task, which traditional methods find difficult to solve.
Aims.
We present our new detection algorithm with wavelets for intracluster light studies (
DAWIS
), which we developed and optimized for the detection of low surface brightness sources in images, in particular (but not limited to) ICL.
Methods.
DAWIS
follows a multiresolution vision based on wavelet representation to detect sources. It is embedded in an iterative procedure called synthesis-by-analysis approach to restore the unmasked light distribution of these sources with very good quality. The algorithm is built so that sources can be classified based on criteria depending on the analysis goal. We present the case of ICL detection and the measurement of ICL fractions. We test the efficiency of
DAWIS
on 270 mock images of galaxy clusters with various ICL profiles and compare its efficiency to more traditional ICL detection methods such as the surface brightness threshold method. We also run
DAWIS
on a real galaxy cluster image, and compare the output to results obtained with previous multiscale analysis algorithms.
Results.
We find in simulations that
DAWIS
is on average able to separate galaxy light from ICL more efficiently, and to detect a greater quantity of ICL flux because of the way sky background noise is treated. We also show that the ICL fraction, a metric used on a regular basis to characterize ICL, is subject to several measurement biases on galaxies and ICL fluxes. In the real galaxy cluster image,
DAWIS
detects a faint and extended source with an absolute magnitude two orders brighter than previous multiscale methods.
Distant galaxy clusters provide important tests of the growth of large-scale structure in addition to highlighting the process of galaxy evolution in a consistently defined environment at large ...look-back time. We present a sample of 22 distant (z > 0.8) galaxy clusters and cluster candidates selected from the 9 deg2 footprint of the overlapping X-ray Multi Mirror (XMM) Large Scale Structure (LSS), CFHTLS-Wide and Spitzer-SWIRE surveys. Clusters are selected as extended X-ray sources with an accompanying overdensity of galaxies displaying optical to mid-infrared photometry consistent with z > 0.8. Nine clusters have confirmed spectroscopic redshifts in the interval 0.8 < z < 1.2, four of which are presented here for the first time. A further 11 candidate clusters have between 8 and 10 band photometric redshifts in the interval 0.8 < z < 2.2, while the remaining two candidates do not have information in sufficient wavebands to generate a reliable photometric redshift. All of the candidate clusters reported in this paper are presented for the first time. Those confirmed and candidate clusters with available near-infrared photometry display evidence for a red sequence galaxy population, determined either individually or via a stacking analysis, whose colour is consistent with the expectation of an old, coeval stellar population observed at the cluster redshift. We further note that the sample displays a large range of red fraction values indicating that the clusters may be at different stages of red sequence assembly. We compare the observed X-ray emission to the flux expected from a suite of model clusters and find that the sample displays an effective mass limit M
200 ∼ 1 × 1014 M with all clusters displaying masses consistent with M
200 < 5 × 1014 M. This XMM distant cluster study represents a complete sample of X-ray-selected z > 0.8 clusters. We discuss the importance of this sample to investigate the abundance of high-redshift clusters and to provide a relatively unbiased view of distant cluster galaxy populations.
Revised distances of Northern HII regions Russeil, D.; Adami, C.; Georgelin, Y. M.
Astronomy and astrophysics (Berlin),
07/2007, Letnik:
470, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Aims.Our aim is to determine the distance of outer Galaxy star-forming complexes in order to model the kinematic structure of our Galaxy. Methods.We searched for exciting star(s) of HII regions, with ...poor or unknown stellar distance, in the second and third galactic quadrants. We carried out spectroscopic and photometric (when necessary) observations in order to establish their spectral type and their U, B and V magnitudes. From these data, complemented with literature data, we determine the spectro-photometric distance of their associated complexes. Results.We (re)established the stellar distance of 23 star forming complexes. Reinvestigating the kinematics of the Perseus and Cygnus arms, we determined the velocity departures from circular rotation and we interpreted them as streaming motions in the spiral arms. Indeed, in addition to the Perseus arm where such departures were known for a long time, we added evidence for velocity deviations in the Cygnus arm. Most significant is that we found the opposite sign for these departures in the Perseus and Cygnus arms, which suggests that the co-rotation radius is located between these two arms at ~13 kpc from the galactic center.
This paper presents 52 X-ray bright galaxy clusters selected within the 11 deg2
XMM-LSS survey. 51 of them have spectroscopic redshifts (0.05 < z < 1.06), one is identified at z
phot = 1.9, 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 T
X = 2 keV), luminosities (median L
X, 500 = 5 × 1043 erg s−1) and total mass estimates (median 5 × 1013 h
−1 M⊙) are measured, adapting to the specific signal-to-noise regime of XMM-LSS observations. Particular care is taken in deriving the sample selection function by means of realistic simulations reproducing the main characteristics of XMM observations. The redshift distribution of clusters shows a deficit of sources when compared to the cosmological expectations, regardless of whether Wilkinson Microwave Anisotropy Probe-9 or Planck-2013 cosmic microwave background parameters are assumed. This lack of sources is particularly noticeable at 0.4 ≲ z ≲ 0.9. However, after quantifying uncertainties due to small number statistics and sample variance, we are not able to put firm (i.e. >3σ) 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 L
X-T
X 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 L
X-T
X-z space, properly accounting for selection biases. We also 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. We provide in a table the catalogue of 52 clusters together with their measured properties.
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