Using a sample of 123 X-ray clusters and groups drawn from the XMM Cluster Survey first data release, we investigate the interplay between the brightest cluster galaxy (BCG), its black hole and the ...intracluster/group medium (ICM). It appears that for groups and clusters with a BCG likely to host significant active galactic nuclei (AGN) feedback, gas cooling dominates in those with T
X > 2 keV while AGN feedback dominates below. This may be understood through the subunity exponent found in the scaling relation we derive between the BCG mass and cluster mass over the halo mass range 1013 < M
500 < 1015 M⊙ and the lack of correlation between radio luminosity and cluster mass, such that BCG AGN in groups can have relatively more energetic influence on the ICM. The L
X-T
X relation for systems with the most massive BCGs, or those with BCGs co-located with the peak of the ICM emission, is steeper than that for those with the least massive and most offset, which instead follows self-similarity. This is evidence that a combination of central gas cooling and powerful, well fuelled AGN causes the departure of the ICM from pure gravitational heating, with the steepened relation crossing self-similarity at T
X= 2 keV. Importantly, regardless of their black hole mass, BCGs are more likely to host radio-loud AGN if they are in a massive cluster (T
X≳ 2 keV) and again co-located with an effective fuel supply of dense, cooling gas. This demonstrates that the most massive black holes appear to know more about their host cluster than they do about their host galaxy. The results lead us to propose a physically motivated, empirical definition of 'cluster' and 'group', delineated at 2 keV.
Objective
To identify and critically appraise the literature on the psychosocial outcomes of orthognathic surgery, reflect on the clinical and theoretical implications, and suggest avenues for future ...research.
Design
A search of the literature was completed using the databases Web of Science, MEDLINE, and PsycINFO to identify English-language articles published since January 2001 that have reported a measure of psychosocial functioning posttreatment.
Results
A total of 38 articles were eligible for inclusion in the review. The studies reported improvements in areas such as satisfaction with facial appearance, self-confidence, self-esteem, anxiety, and social functioning. Small percentages of patients were left dissatisfied or had difficulty adjusting to appearance change despite the absence of treatment complications. Gains in psychosocial functioning were maintained over several years, and satisfaction increased over time.
Conclusions
There are consistent positive outcomes reported as a result of orthognathic surgery, but conclusions are limited by methodological issues in study design such as small sample sizes, limited use of control groups, and measures that fail to tap into relevant areas of psychosocial functioning. In addition, further exploration is required of processes such as adjustment to facial change and the role of psychological support during treatment.
Large surveys using the Sunyaev-Zel'dovich (SZ) effect to find clusters of galaxies are now starting to yield large numbers of systems out to high redshift, many of which are new discoveries. In ...order to provide theoretical interpretation for the release of the full SZ cluster samples over the next few years, we have exploited the large-volume Millennium gas cosmological N-body hydrodynamics simulations to study the SZ cluster population at low and high redshift, for three models with varying gas physics. We confirm previous results using smaller samples that the intrinsic (spherical) Y
500-M
500 relation has very little scatter (
), is insensitive to cluster gas physics and evolves to redshift 1 in accordance with self-similar expectations. Our preheating and feedback models predict scaling relations that are in excellent agreement with the recent analysis from combined Planck and XMM-Newton data by the Planck Collaboration. This agreement is largely preserved when r
500 and M
500 are derived using the hydrostatic mass proxy, Y
X, 500, albeit with significantly reduced scatter (
), a result that is due to the tight correlation between Y
500 and Y
X, 500. Interestingly, this assumption also hides any bias in the relation due to dynamical activity. We also assess the importance of projection effects from large-scale structure along the line of sight, by extracting cluster Y
500 values from 50 simulated 5 × 5-deg2 sky maps. Once the (model-dependent) mean signal is subtracted from the maps we find that the integrated SZ signal is unbiased with respect to the underlying clusters, although the scatter in the (cylindrical) Y
500-M
500 relation increases in the preheating case, where a significant amount of energy was injected into the intergalactic medium at high redshift. Finally, we study the hot gas pressure profiles to investigate the origin of the SZ signal and find that the largest contribution comes from radii close to r
500 in all cases. The profiles themselves are well described by generalized Navarro, Frenk & White profiles but there is significant cluster-to-cluster scatter. In conclusion, our results support the notion that Y
500 is a robust mass proxy for use in cosmological analyses with clusters.
The XMM Cluster Survey: X-ray analysis methodology Lloyd-Davies, E. J.; Romer, A. Kathy; Mehrtens, Nicola ...
Monthly notices of the Royal Astronomical Society,
November 2011, Letnik:
418, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters using all publicly available data in the XMM-Newton Science Archive. Its main aims are to measure cosmological parameters ...and trace the evolution of X-ray scaling relations. In this paper we describe the data processing methodology applied to the 5776 XMM observations used to construct the current XCS source catalogue. A total of 3675 > 4σ cluster candidates with >50 background-subtracted X-ray counts are extracted from a total non-overlapping area suitable for cluster searching of 410 deg2. Of these, 993 candidates are detected with >300 background-subtracted X-ray photon counts, and we demonstrate that robust temperature measurements can be obtained down to this count limit. We describe in detail the automated pipelines used to perform the spectral and surface brightness fitting for these candidates, as well as to estimate redshifts from the X-ray data alone. A total of 587 (122) X-ray temperatures to a typical accuracy of <40 (<10) per cent have been measured to date. We also present the methodology adopted for determining the selection function of the survey, and show that the extended source detection algorithm is robust to a range of cluster morphologies by inserting mock clusters derived from hydrodynamical simulations into real XMMimages. These tests show that the simple isothermal β-profiles is sufficient to capture the essential details of the cluster population detected in the archival XMM observations. The redshift follow-up of the XCS cluster sample is presented in a companion paper, together with a first data release of 503 optically confirmed clusters.
An Introduction to Modern Cosmology Third Edition is an accessible account of modern cosmological ideas. The Big Bang Cosmology is explored, looking at its observational successes in explaining the ...expansion of the Universe, the existence and properties of the cosmic microwave background, and the origin of light elements in the universe. Properties of the very early Universe are also covered, including the motivation for a rapid period of expansion known as cosmological inflation. The third edition brings this established undergraduate textbook up-to-date with the rapidly evolving observational situation. This fully revised edition of a bestseller takes an approach which is grounded in physics with a logical flow of chapters leading the reader from basic ideas of the expansion described by the Friedman equations to some of the more advanced ideas about the early universe. It also incorporates up-to-date results from the Planck mission, which imaged the anisotropies of the Cosmic Microwave Background radiation over the whole sky. The Advanced Topic sections present subjects with more detailed mathematical approaches to give greater depth to discussions. Student problems with hints for solving them and numerical answers are embedded in the chapters to facilitate the reader's understanding and learning. Cosmology is now part of the core in many degree programs. This current, clear and concise introductory text is relevant to a wide range of astronomy programs worldwide and is essential reading for undergraduates and Masters students, as well as anyone starting research in cosmology. Supplementary material, including full-colour images, updates and links for students and instructors, is available on the author's website: http://www.roe.ac.uk/~arl/.
We use Chandra X-ray and Spitzer infrared (IR) observations to explore the active galactic nucleus (AGN) and starburst populations of XMMXCS J2215.9-1738 at z = 1.46, one of the most distant ...spectroscopically confirmed galaxy clusters known. The high-resolution X-ray imaging reveals that the cluster emission is contaminated by point sources that were not resolved in XMM-Newton observations of the system, and have the effect of hardening the spectrum, leading to the previously reported temperature for this system being overestimated. From a joint spectroscopic analysis of the Chandra and XMM-Newton data, the cluster is found to have temperature T = 4.1{sup +0.6}{sub -0.9} keV and luminosity L {sub X} = (2.92{sup +0.24} {sub -0.35}) x 10{sup 44} erg s{sup -1}, extrapolated to a radius of 2 Mpc. As a result of this revised analysis, the cluster is found to lie on the {sigma} {sub v}-T relation, but the cluster remains less luminous than would be expected from self-similar evolution of the local L {sub X}-T relation. Two of the newly discovered X-ray AGNs are cluster members, while a third object, which is also a prominent 24 {mu}m source, is found to have properties consistent with it being a high-redshift, highly obscured object in the background. We find a total of eight >5{sigma} 24 {mu}m sources associated with cluster members (four spectroscopically confirmed and four selected using photometric redshifts) and one additional 24 {mu}m source with two possible optical/near-IR counterparts that may be associated with the cluster. Examining the Infrared Array Camera colors of these sources, we find that one object is likely to be an AGN. Assuming that the other 24 {mu}m sources are powered by star formation, their IR luminosities imply star formation rates {approx}100 M{sub sun} yr{sup -1}. We find that three of these sources are located at projected distances of <250 kpc from the cluster center, suggesting that a large amount of star formation may be taking place in the cluster core, in contrast to clusters at low redshift.
ABSTRACT
The Sunyaev–Zel'dovich (SZ) effect is a powerful new tool for finding and studying clusters at high redshift, particularly in combination with their X‐ray properties. In this paper we ...quantify the expected scaling relations between these properties using numerical simulations with various models for heating and cooling of the cluster gas. For a Non‐radiative model, we find scaling relations in good agreement with self‐similar predictions: Y∝T5/2X and Y∝L5/4X. Our main results focus on predictions from Cooling and Preheating simulations, shown recently by Muanwong et al. to provide a good match to the X‐ray scaling relations at z= 0. For these runs, we find slopes of approximately Y∝T3X and Y∝LX, steeper and flatter than the self‐similar scalings respectively. We also study the redshift evolution of the scaling relations, and find that the slopes show no evidence of evolution out to redshifts well beyond unity, while the normalizations of relations between the SZ signal and X‐ray properties do show evolution relative to that expected from self‐similarity, particularly at z < 1.
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