scholarly journals Simulations of the merging galaxy cluster Abell 2034: what determines the level of separation between gas and dark matter

2020 ◽  
Vol 500 (2) ◽  
pp. 1858-1869 ◽  
Author(s):  
Micheli T Moura ◽  
Rubens E G Machado ◽  
Rogério Monteiro-Oliveira
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Galaxy Cluster ◽  
X Rays ◽  
X Ray ◽  
History Of ◽  
Hydrodynamical Simulations ◽  
Cluster Mergers ◽  
Cluster Cores ◽  
Intracluster Gas

ABSTRACT Cluster mergers are an important laboratory for studying the behaviour of dark matter (DM) and intracluster gas. There are dissociative collisions that can separate the intracluster gas from the DM. Abell 2034 presents clear dissociative features observed by X-rays and gravitational lensing. The cluster, at z = 0.114, consists of two substructures with mass ratio of about 1:2.2, separated by ∼720 kpc. The X-ray emission peak is offcentred from the south DM peak by ∼350 kpc. Using N-body hydrodynamical simulations, we aim to reconstruct the dynamic history of the collision, reproducing the observed features, and also to explore the conditions that led to the dissociation. Our best model assuming that the collision is close to the plane of the sky, with a small impact parameter, observed 0.26 Gyr after central passage, reproduces the observed features of this cluster, such as the offset between X-ray and DM peaks, X-ray morphology, and temperatures. We explored several variations using different gas and DM concentrations for each cluster. The level of dissociation was quantified by the distances between X-ray and DM peaks, and also by the gas retention in the cluster cores. We found that the ratio of central gas densities is more important than the ratio of central DM densities in determining the level of dissociation.

scholarly journals Simulations of gas sloshing induced by a newly discovered gas poor substructure in galaxy cluster Abell 1644

2020 ◽  
Vol 495 (2) ◽  
pp. 2022-2034 ◽  
Author(s):  
L Doubrawa ◽  
R E G Machado ◽  
T F Laganá ◽  
G B Lima Neto ◽  
R Monteiro-Oliveira ◽  
...  
Keyword(s):  
Galaxy Cluster ◽  
Nearby Galaxy ◽  
X Ray ◽  
Current State ◽  
History Of ◽  
Best Fitting ◽  
Hydrodynamical Simulations ◽  
Temperature Maps ◽  
Intracluster Gas ◽  
Good Agreement

ABSTRACT Collision events lead to peculiar morphologies in the intracluster gas of galaxies clusters. That seems to be the case of Abell 1644, a nearby galaxy cluster, composed of three main structures: the southern cluster that exhibits a spiral-like morphology, A1644S; the northern cluster seen in X-ray observations, A1644N1; and the recently discovered substructure, A1644N2. By means of N-body hydrodynamical simulations, we attempt to reconstruct the dynamical history of this system. These simulations resulted in two specific scenarios: (i) The collision between A1644S and A1644N2. Our best model has an inclination between the merger plane and the plane of the sky of 30°, and reaches the best morphology 1.6 Gyr after the pericentric passage. At this instant A1644N2 is gas poor, becoming nearly undetectable in X-ray emission. This model shows a good agreement with observations; (ii) The collision between A1644S and A1644N1. This approach did not give rise to results as satisfactory as the first scenario, due to great disturbances in density and mismatching temperature maps. As a complementary study, we perform a three-cluster simulation using as base the best-fitting model to reproduce the current state of A1644 with the three main structures. This scenario presented a good agreement to the global morphology of the observations. Thus, we find that the more likely scenario is a collision between A1644S and the newly discovered A1644N2, where A1644N1 may be present as long as it does not greatly interfere in the formation of the spiral feature.

scholarly journals The 3XMM/SDSS Stripe 82 Galaxy Cluster Survey – II. X-ray and optical properties of the cluster sample

2019 ◽  
Vol 486 (4) ◽  
pp. 4863-4879 ◽  
Author(s):  
Ali Takey ◽  
Florence Durret ◽  
Isabel Márquez ◽  
Amael Ellien ◽  
Mona Molham ◽  
...  
Keyword(s):  
Optical Properties ◽  
Galaxy Cluster ◽  
X Rays ◽  
Present Sample ◽  
X Ray ◽  
Cluster Galaxies ◽  
Cluster Survey ◽  
Cluster Sample ◽  
Cluster Mass ◽  
First Time

ABSTRACT We present X-ray and optical properties of the optically confirmed galaxy cluster sample from the 3XMM/SDSS Stripe 82 cluster survey. The sample includes 54 galaxy clusters in the redshift range of 0.05–1.2, with a median redshift of 0.36. We first present the X-ray temperature and luminosity measurements that are used to investigate the X-ray luminosity–temperature relation. The slope and intercept of the relation are consistent with those published in the literature. Then, we investigate the optical properties of the cluster galaxies including their morphological analysis and the galaxy luminosity functions (GLFs). The morphological content of cluster galaxies is investigated as a function of cluster mass and distance from the cluster centre. No strong variation of the fraction of early- and late-type galaxies with cluster mass is observed. The fraction of early-type galaxies as a function of cluster radius varies as expected. The individual GLFs of red sequence galaxies were studied in the five ugriz bands for 48 clusters. The GLFs were then stacked in three mass bins and two redshift bins. Twenty clusters of the present sample are studied for the first time in X-rays, and all are studied for the first time in the optical range. Altogether, our sample appears to have X-ray and optical properties typical of ‘average’ cluster properties.

scholarly journals Revising the merger scenario of the galaxy cluster Abell 1644: a new gas poor structure discovered by weak gravitational lensing

2020 ◽  
Vol 495 (2) ◽  
pp. 2007-2021 ◽  
Author(s):  
R Monteiro-Oliveira ◽  
L Doubrawa ◽  
R E G Machado ◽  
G B Lima Neto ◽  
M Castejon ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Elliptical Galaxy ◽  
Galaxy Cluster ◽  
X Ray ◽  
The North ◽  
Density Maps ◽  
Hydrodynamical Simulation ◽  
The Galaxy ◽  
Maximum Separation ◽  
Comprehensive Study

ABSTRACT The galaxy cluster Abell 1644 ($\bar{z}=0.047$) is known for its remarkable spiral-like X-ray emission. It was previously identified as a bimodal system, comprising the subclusters, A1644S and A1644N, each one centred on a giant elliptical galaxy. In this work, we present a comprehensive study of this system, including new weak lensing and dynamical data and analysis plus a tailor-made hydrodynamical simulation. The lensing and galaxy density maps showed a structure in the North that could not be seen on the X-ray images. We, therefore, rename the previously known northern halo as A1644N1 and the new one as A1644N2. Our lensing data suggest that those have fairly similar masses: $M_{200}^{\rm N1}=0.90_{-0.85}^{+0.45} \times 10^{14}$ and $M_{200}^{\rm N2}=0.76_{-0.75}^{+0.37} \times 10^{14}$ M⊙, whereas the southern structure is the main one: $M_{200}^{\rm S}=1.90_{-1.28}^{+0.89}\times 10^{14}$ M⊙. Based on the simulations, fed by the observational data, we propose a scenario where the remarkable X-ray characteristics in the system are the result of a collision between A1644S and A1644N2 that happened ∼1.6 Gyr ago. Currently, those systems should be heading to a new encounter, after reaching their maximum separation.

scholarly journals X-ray Spectra of Clusters of Galaxies

1990 ◽  
Vol 115 ◽  
pp. 209-218 ◽  
Author(s):  
Craig L. Sarazin
Keyword(s):  
High Resolution ◽  
Absorption Line ◽  
Physical State ◽  
Thermal Emission ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
Line Measurement ◽  
History Of ◽  
Intracluster Gas ◽  
X Ray Absorption

AbstractX-ray line observations of clusters of galaxies have shown that the X-ray emission in clusters is mainly thermal emission from hot diffuse gas, and that much of this gas has come out of stars, probably having been ejected from galaxies in the cluster. Future high resolution observations should allow us to determine the physical state of the gas. X-ray line measurements and abundance determinations can lead to strong constraints on the origin of the intracluster gas, and on the chemical evolution and history of galaxies. Some of the stronger resonant X-ray lines may be observable as absorption lines against a background quasar. Such X-ray absorption line measurement can be used to directly derive distances to clusters, using a technique similar to (and possibly complementary to) that the well-known method using the Zel’dovich-Syunyaev effect.

scholarly journals Projection effects in galaxy cluster samples: insights from X-ray redshifts

2019 ◽  
Vol 626 ◽  
pp. A48 ◽  
Author(s):  
M. E. Ramos-Ceja ◽  
F. Pacaud ◽  
T. H. Reiprich ◽  
K. Migkas ◽  
L. Lovisari ◽  
...  
Keyword(s):  
Spatial Information ◽  
Galaxy Cluster ◽  
X Rays ◽  
X Ray ◽  
Cluster Sample ◽  
Global Cluster ◽  
Sky Survey ◽  
The Galaxy ◽  
Flux Measurements ◽  
Cluster Properties

Presently, the largest sample of galaxy clusters selected in X-rays comes from the ROSAT All-Sky Survey (RASS). Although there have been many interesting clusters discovered with the RASS data, the broad point spread function of the ROSAT satellite limits the attainable amount of spatial information for the detected objects. This leads to the discovery of new cluster features when a re-observation is performed with higher-resolution X-ray satellites. Here we present the results from XMM-Newton observations of three clusters: RXC J2306.6−1319, ZwCl 1665, and RXC J0034.6−0208, for which the observations reveal a double or triple system of extended components. These clusters belong to the extremely expanded HIghest X-ray FLUx Galaxy Cluster Sample (eeHIFLUGCS), which is a flux-limited cluster sample (fX, 500 ≥ 5 × 10−12 erg s−1 cm−2 in the 0.1−2.4 keV energy band). For each structure in each cluster, we determine the redshift with the X-ray spectrum and find that the components are not part of the same cluster. This is confirmed by an optical spectroscopic analysis of the galaxy members. Therefore, the total number of clusters is actually seven, rather than three. We derive global cluster properties of each extended component. We compare the measured properties to lower-redshift group samples, and find a good agreement. Our flux measurements reveal that only one component of the ZwCl 1665 cluster has a flux above the eeHIFLUGCS limit, while the other clusters will no longer be part of the sample. These examples demonstrate that cluster–cluster projections can bias X-ray cluster catalogues and that with high-resolution X-ray follow-up this bias can be corrected.

scholarly journals Probing cosmic isotropy with a new X-ray galaxy cluster sample through the LX–T scaling relation

2020 ◽  
Vol 636 ◽  
pp. A15 ◽  
Author(s):  
K. Migkas ◽  
G. Schellenberger ◽  
T. H. Reiprich ◽  
F. Pacaud ◽  
M. E. Ramos-Ceja ◽  
...  
Keyword(s):  
Galaxy Clusters ◽  
Statistical Significance ◽  
Cosmological Parameters ◽  
Galaxy Cluster ◽  
Temperature Measurements ◽  
Joint Analysis ◽  
Scaling Relations ◽  
Exact Nature ◽  
X Rays ◽  
X Ray

The isotropy of the late Universe and consequently of the X-ray galaxy cluster scaling relations is an assumption greatly used in astronomy. However, within the last decade, many studies have reported deviations from isotropy when using various cosmological probes; a definitive conclusion has yet to be made. New, effective and independent methods to robustly test the cosmic isotropy are of crucial importance. In this work, we use such a method. Specifically, we investigate the directional behavior of the X-ray luminosity-temperature (LX–T) relation of galaxy clusters. A tight correlation is known to exist between the luminosity and temperature of the X-ray-emitting intracluster medium of galaxy clusters. While the measured luminosity depends on the underlying cosmology through the luminosity distance DL, the temperature can be determined without any cosmological assumptions. By exploiting this property and the homogeneous sky coverage of X-ray galaxy cluster samples, one can effectively test the isotropy of cosmological parameters over the full extragalactic sky, which is perfectly mirrored in the behavior of the normalization A of the LX–T relation. To do so, we used 313 homogeneously selected X-ray galaxy clusters from the Meta-Catalogue of X-ray detected Clusters of galaxies. We thoroughly performed additional cleaning in the measured parameters and obtain core-excised temperature measurements for all of the 313 clusters. The behavior of the LX–T relation heavily depends on the direction of the sky, which is consistent with previous studies. Strong anisotropies are detected at a ≳4σ confidence level toward the Galactic coordinates (l, b) ∼ (280°, − 20°), which is roughly consistent with the results of other probes, such as Supernovae Ia. Several effects that could potentially explain these strong anisotropies were examined. Such effects are, for example, the X-ray absorption treatment, the effect of galaxy groups and low redshift clusters, core metallicities, and apparent correlations with other cluster properties, but none is able to explain the obtained results. Analyzing 105 bootstrap realizations confirms the large statistical significance of the anisotropic behavior of this sky region. Interestingly, the two cluster samples previously used in the literature for this test appear to have a similar behavior throughout the sky, while being fully independent of each other and of our sample. Combining all three samples results in 842 different galaxy clusters with luminosity and temperature measurements. Performing a joint analysis, the final anisotropy is further intensified (∼5σ), toward (l, b) ∼ (303°, − 27°), which is in very good agreement with other cosmological probes. The maximum variation of DL seems to be ∼16 ± 3% for different regions in the sky. This result demonstrates that X-ray studies that assume perfect isotropy in the properties of galaxy clusters and their scaling relations can produce strongly biased results whether the underlying reason is cosmological or related to X-rays. The identification of the exact nature of these anisotropies is therefore crucial for any statistical cluster physics or cosmology study.

Clinical Joint Outcome after Joint Bleeds in Patients with Von Willebrand Disease Is Comparable to Moderate and Severe Hemophilia A Despite Fewer Joint Bleeds

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3789-3789 ◽  
Author(s):  
Karin PM van Galen ◽  
Merel Timmer ◽  
Piet de Kleijn ◽  
Frank W.G. Leebeek ◽  
Roger E.G. Schutgens ◽  
...  
Keyword(s):  
Physical Examination ◽  
Research Funding ◽  
Functional Limitations ◽  
Joint Damage ◽  
Von Willebrand Disease ◽  
X Rays ◽  
X Ray ◽  
History Of ◽  
Type 3 ◽  
Von Willebrand

Abstract Background Recurrent joint bleeds are the main cause of joint deterioration (hemophilic arthropathy) in patients with hemophilia. To what extent arthropathy occurs following joint bleeds in patients with Von Willebrand disease (VWD) compared to hemophilia has never been studied. Objectives The primary objective was to compare joint outcome by physical examination between adults with VWD and moderate and severe hemophilia A (HA). The main secondary objectives were to compare joint bleed frequency, radiological joint damage and self-reported functional limitations between VWD and moderate and severe HA. Methods We selected adult patients with VWD (VWF activity <30%) and moderate or severe HA, who had a medical history of treatment for joint bleeds, for this post hoc analysis. To compare joint outcome we used the Hemophilia Joint Health Score (HJHS range 0-124, obtained by physical examination), X-ray Pettersson scores of ankles, knees and elbows (PS range 0-13 per joint) and Hemophilia Activities List scores, a patient administered questionnaire measuring functional limitations (HAL range 0-100). Univariate analyses were performed using Mann Whitney U and Chi2. For multivariate analysis we used negative binomial regression analysis (HJHS) and logistic regression (dichotomized PS>3 and HAL<95) adjusted for age. We performed a subgroup analysis of the patients with type 3 VWD. Results We included 48 patients with VWD, 39 with moderate and 59 with severe HA. The mean age was 45, 38 and 26 years, respectively. Fewer patients with VWD than HA had a lifetime history of more than 5 joint bleeds (56% VWD vs. 77% moderate HA vs. 98% severe HA, p<0.001). Joint dysfunction at physical examination was comparable between the patients with VWD and moderate HA (median HJHS 5 vs. 5.5, p=0.65) but slightly better in VWD compared to severe HA (median HJHS 5 vs. 9, p=0.02). Apparent joint damage on X rays (PS>3 of one or more joints) occurred in 12/46 patients with VWD compared to 27/40 patients with severe HA (26% vs. 68%: OR 0.09; 95%CI 0.03-0.34, p<0.001). In moderate HA insufficient X rays were available for analyses. Functional limitations according to the HAL were comparable between patients with VWD and moderate and severe HA (VWD median HAL total score 88 vs. 95 in both moderate and severe HA, p=0.35). The subgroup analysis of joint dysfunction in patients with type 3 VWD (n=19, median age 40) showed clinical changes comparable to severe HA (median HJHS 14 vs. 9, p=0.83). We found a trend towards less radiological joint damage in type 3 VWD compared to severe HA (PS>3: 47% vs. 68%, OR 0.28; 95%CI 0.07-1.12, p=0.07). However, patients with type 3 VWD reported more functional limitations compared to those with moderate or severe HA (median HAL total score 77 vs. 95, p=0.01; adjusted for age OR 0.38; 95%CI 0.1-1.2, p=0.10). Conclusions Despite fewer joint bleeds, joint function according to the HJHS was comparable between adult patients with VWD and moderate HA with a history of treatment for joint bleeds. Apparent X ray joint damage occurred less often in patients with VWD compared to those with severe HA. The HJHS of patients with type 3 VWD was comparable to those with severe HA, but the patients with type 3 VWD reported more functional limitations, partly explained by their higher age. Knowledge of similarities and differences in joint outcome between VWD and hemophilia can be helpful to improve the awareness and treatment of joint bleeds in VWD to prevent arthropathy and functional limitations. Disclosures van Galen: Bayer: Research Funding; CSL Behring: Research Funding; Baxter: Research Funding. Leebeek:CSL Behring: Research Funding; Baxter: Research Funding. Schutgens:Sanquin: Research Funding; CSL Behring: Research Funding. Fischer:Baxalta/Baxter: Consultancy, Research Funding, Speakers Bureau; Pfizer: Consultancy, Research Funding, Speakers Bureau; CSL Behring: Consultancy, Speakers Bureau; NovoNordisk: Consultancy, Research Funding, Speakers Bureau; Octapharma: Speakers Bureau; Baxter: Consultancy, Research Funding, Speakers Bureau; Wyeth: Research Funding; Biogen: Consultancy; Biotest: Consultancy, Speakers Bureau; Bayer: Consultancy, Research Funding, Speakers Bureau; Freeline: Consultancy. Mauser-Bunschoten:CSL Behring: Research Funding; Bayer: Research Funding; Baxter: Research Funding; Griffols: Research Funding; Novo Nordisk: Research Funding; Pfizer: Research Funding; Biovitrum: Research Funding; Saquin: Research Funding.

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