We aimed to test whether childhood bullying victimization increases risk for age-related disease at mid-life using biological markers including inflammation and adiposity, independent of other ...childhood risk factors and key adult variables.
The present study was a 50-year prospective longitudinal birth cohort study of all births in Britain in 1 week in 1958. Exposure to bullying was assessed prospectively when participants were aged 7 and 11 years (27.7% occasionally bullied; 14.6% frequently bullied). Blood inflammation biomarkers C-reactive protein (CRP) and fibrinogen and adiposity body mass index (BMI) and waist:hip ratio were measured at age 45 years.
Participants who had been frequently bullied in childhood showed increased levels of CRP at mid-life β = 0.07, 95% confidence interval (CI) 0.04-0.10 and higher risk for clinically relevant inflammation cut-off CRP > 3 mg/l: 20.4% v. 15.9%, odds ratio (OR) = 1.35, 95% CI 1.12-1.64. Women who were bullied in childhood had higher BMI than non-bullied participants and were at increased risk of being obese (BMI ≥ 30 kg/m2: occasionally bullied: 26.0% v. 19.4%, OR = 1.45, 95% CI 1.18-1.77; frequently bullied: 26.2% v. 19.4%, OR = 1.41, 95% CI 1.09-1.83). Findings remained significant when controlling for childhood risk factors (e.g. parental social class; participants' BMI and psychopathology in childhood) and key adult variables (e.g. adult social class, smoking, diet and exercise).
Bullied children show increases in risk factors for age-related disease in middle adulthood, independent of co-occurring childhood and adult risks. Given the high prevalence of bullying victimization in childhood, tackling this form of psychosocial stress early in life has the potential of reducing risk for age-related disease and its associated burden.
We investigate the form and evolution of the X-ray luminosity-temperature (L
X-kT) relation of a sample of 114 galaxy clusters observed with Chandra at 0.1 < z < 1.3. The clusters were divided into ...subsamples based on their X-ray morphology or whether they host strong cool cores. We find that when the core regions are excluded, the most relaxed clusters (or those with the strongest cool cores) follow an L
X-kT relation with a slope that agrees well with simple self-similar expectations. This is supported by an analysis of the gas density profiles of the systems, which shows self-similar behaviour of the gas profiles of the relaxed clusters outside the core regions. By comparing our data with clusters in the Representative XMM-Newton Cluster Structure Survey (REXCESS) sample, which extends to lower masses, we find evidence that the self-similar behaviour of even the most relaxed clusters breaks at around 3.5 keV. By contrast, the L
X-kT slopes of the subsamples of unrelaxed systems (or those without strong cool cores) are significantly steeper than the self-similar model, with lower mass systems appearing less luminous and higher mass systems appearing more luminous than the self-similar relation. We argue that these results are consistent with a model of non-gravitational energy input in clusters that combines central heating with entropy enhancements from merger shocks. Such enhancements could extend the impact of central energy input to larger radii in unrelaxed clusters, as suggested by our data. We also examine the evolution of the L
X-kT relation, and find that while the data appear inconsistent with simple self-similar evolution, the differences can be plausibly explained by selection bias, and thus we find no reason to rule out self-similar evolution. We show that the fraction of cool core clusters in our (non-representative) sample decreases at z > 0.5 and discuss the effect of this on measurements of the evolution in the L
X-kT relation.
In this paper, we introduce Physically motivated, Internally Consistent Analysis of Cluster Scaling (PICACS), a detailed model of scaling relations between galaxy cluster masses and their observable ...properties. This model can be used to constrain simultaneously the form, scatter (including its covariance) and evolution of the scaling relations, as well as the masses of the individual clusters. In this framework, scaling relations between observables (such as that between X-ray luminosity and temperature) are modelled explicitly in terms of the fundamental mass-observable scaling relations, and so are fully constrained without being fit directly. We apply the PICACS model to two observational data sets, and show that it performs as well as traditional regression methods for simply measuring individual scaling relation parameters, but reveals additional information on the processes that shape the relations while providing self-consistent mass constraints. Our analysis suggests that the observed combination of slopes of the scaling relations can be described by a deficit of gas in low-mass clusters that is compensated for by elevated gas temperatures, such that the total thermal energy of the gas in a cluster of given mass remains close to self-similar expectations. This is interpreted as the result of AGN feedback removing low entropy gas from low-mass systems, while heating the remaining gas. We deconstruct the luminosity-temperature (L-T) relation and show that its steepening compared to self-similar expectations can be explained solely by this combination of gas depletion and heating in low-mass systems, without any additional contribution from a mass dependence of the gas structure. Finally, we demonstrate that a self-consistent analysis of the scaling relations leads to an expectation of self-similar evolution of the L-T relation that is significantly weaker than is commonly assumed.
We present Chandra observations of 23 galaxy groups and low-mass galaxy clusters at 0.03 < z < 0.15 with a median temperature of
${\sim }2{{\rm keV}}$
. The sample is a statistically complete ...flux-limited subset of the 400 deg2 survey. We investigated the scaling relation between X-ray luminosity (L) and temperature (T), taking selection biases fully into account. The logarithmic slope of the bolometric L–T relation was found to be 3.29 ± 0.33, consistent with values typically found for samples of more massive clusters. In combination with other recent studies of the L–T relation, we show that there is no evidence for the slope, normalization, or scatter of the L–T relation of galaxy groups being different than that of massive clusters. The exception to this is that in the special case of the most relaxed systems, the slope of the core-excised L–T relation appears to steepen from the self-similar value found for massive clusters to a steeper slope for the lower mass sample studied here. Thanks to our rigorous treatment of selection biases, these measurements provide a robust reference against which to compare predictions of models of the impact of feedback on the X-ray properties of galaxy groups.
The XXL Survey Pacaud, F; Clerc, N; Giles, P A ...
Astronomy and astrophysics (Berlin),
08/2016, Letnik:
592
Journal Article
Recenzirano
Odprti dostop
Context. The XXL Survey is the largest survey carried out by the XMM-Newton satellite and covers a total area of 50 square degrees distributed over two fields. It primarily aims at investigating the ...large-scale structures of the Universe using the distribution of galaxy clusters and active galactic nuclei as tracers of the matter distribution. The survey will ultimately uncover several hundreds of galaxy clusters out to a redshift of ~2 at a sensitivity of ~10 super(-14) ergs super(-1)cm super(-2) in the 0.5-2 keV band. Aims. This article presents the XXL bright cluster sample, a subsample of 100 galaxy clusters selected from the full XXL catalogue by setting a lower limit of 3 x 10 super(-14) erg s super(-1) cm super(-2) on the source flux within a 1? aperture. Methods. The selection function was estimated using a mixture of Monte Carlo simulations and analytical recipes that closely reproduce the source selection process. An extensive spectroscopic follow-up provided redshifts for 97 of the 100 clusters. We derived accurate X-ray parameters for all the sources. Scaling relations were self-consistently derived from the same sample in other publications of the series. On this basis, we study the number density, luminosity function, and spatial distribution of the sample. Results. The bright cluster sample consists of systems with masses between M sub(500)= 7 x 10 super(13) and 3 x 10 super(14)M sub(?), mostly located between z= 0.1 and 0.5. The observed sky density of clusters is slightly below the predictions from the WMAP9 model, and significantly below the prediction from the Planck 2015 cosmology. In general, within the current uncertainties of the cluster mass calibration, models with higher values of sigma sub(8) and/or Omega sub(M) appear more difficult to accommodate. We provide tight constraints on the cluster differential luminosity function and find no hint of evolution out to z~ 1. We also find strong evidence for the presence of large-scale structures in the XXL bright cluster sample and identify five new superclusters.
We use a sample of 115 galaxy clusters at 0.1 < z < 1.3 observed with Chandra ACIS-I to investigate the relation between luminosity and Y(x (the product of gas mass and temperature). The scatter in ...the relation is dominated by cluster cores, and a tight L(x - Y(x relation (11% intrinsic scatter in L(x) is recovered if sufficiently large core regions (0.15R(500)) are excluded. The intrinsic scatter is well described by a lognormal distribution, and the relations are consistent for relaxed and disturbed/merging clusters. We investigate the L(x - Y(x relation in low-quality data (e.g., for clusters detected in X-ray survey data) by estimating L(x from soft-band count rates, and find that the scatter increases somewhat to 21%. We confirm the tight correlation between Y(x and mass and the self-similar evolution of that scaling relation out to z = 0.6 for a subset of clusters in our sample with mass estimates from the literature. This is used to estimate masses for the entire sample and hence measure the L(x - M relation. We find that the scatter in the L(x - M relation is much lower than previous estimates, due to the full removal of cluster cores and more robust mass estimates. For high-redshift clusters the scatter in the L(x - M relation remains low if cluster cores are not excluded. These results suggest that cluster masses can be reliably estimated from simple luminosity measurements in low-quality data where direct mass estimates, or measurements of Y(x, are not possible. This has important applications in the estimation of cosmological parameters from X-ray cluster surveys.
We have assembled a sample of 115 galaxy clusters at 0.1 < z < 1.3 with archived Chandra ACIS-I observations. We present X-ray images of the clusters and make available region files containing ...contours of the smoothed X-ray emission. The structural properties of the clusters were investigated, and we found a significant absence of relaxed clusters (as determined by centroid shift measurements) at z > 0.5. The slope of the surface brightness profiles at large radii were steeper on average by 15% than the slope obtained by fitting a simple beta -model to the emission. This slope was also found to be correlated with cluster temperature, with some indication that the correlation is weaker for the clusters at z > 0.5. We measured the mean metal abundance of the cluster gas as a function of redshift and found significant evolution, with the abundances dropping by 50% between z = 0.1 and z approximately 1. This evolution was still present (although less significant) when the cluster cores were excluded from the abundance measurements, indicating that the evolution is not solely due to the disappearance of relaxed, cool core clusters (which are known to have enhanced core metal abundances) from the population at z unk 0.5.
The XXL Survey Pacaud, F.; Pierre, M.; Melin, J.-B. ...
Astronomy and astrophysics (Berlin),
12/2018, Letnik:
620
Journal Article
Recenzirano
Odprti dostop
Context.
We present an estimation of cosmological parameters with clusters of galaxies.
Aims.
We constrain the Ω
m
,
σ
8
, and
w
parameters from a stand-alone sample of X-ray clusters detected in the ...50 deg
2
XMM-XXL survey with a well-defined selection function.
Methods.
We analyse the redshift distribution of a sample comprising 178 high signal-to-noise ratio clusters out to a redshift of unity. The cluster sample scaling relations are determined in a self-consistent manner.
Results.
In a lambda cold dark matter (ΛCDM) model, the cosmology favoured by the XXL clusters compares well with results derived from the
Planck
Sunyaev-Zel’dovich clusters for a totally different sample (mass/redshift range, selection biases, and scaling relations). However, with this preliminary sample and current mass calibration uncertainty, we find no inconsistency with the
Planck
CMB cosmology. If we relax the
w
parameter, the
Planck
CMB uncertainties increase by a factor of ~10 and become comparable with those from XXL clusters. Combining the two probes allows us to put constraints on Ω
m
= 0.316 ± 0.060,
σ
8
= 0.814 ± 0.054, and
w
= −1.02 ± 0.20.
Conclusions.
This first self-consistent cosmological analysis of a sample of serendipitous XMM clusters already provides interesting insights into the constraining power of the XXL survey. Subsequent analysis will use a larger sample extending to lower confidence detections and include additional observable information, potentially improving posterior uncertainties by roughly a factor of 3.
Aims. Based on XMM-Newton, Chandra, and SDSS data, we investigate the baryon distribution in groups and clusters and its use as a cosmological constraint. For this, we considered a sample of 123 ...systems with temperatures kT500 = 1.0−9.0 keV, total masses in the mass range M500 = (~1013-4 × 1015)h70-1 M⊙, and redshifts 0.02 < z < 1.3. Methods. The gas masses and total masses are derived from X-ray data under the assumption of hydrostatic equilibrium and spherical symmetry. The stellar masses are based on SDSS-DR8 optical photometric data. For the 37 systems out of 123 that had both optical and X-ray data available, we investigated the gas, stellar, and total baryon mass fractions inside r2500 and r500 and the differential gas mass fraction within the spherical annulus between r2500 and r500, as a function of total mass. For the other objects, we investigated the gas mass fraction only. Results. We find that the gas mass fraction inside r2500 and r500 depends on the total mass. However, the differential gas mass fraction does not show any dependence on total mass for systems with M500 > 1014 M⊙. The stellar mass fraction inside r2500 and r500 increases towards low-mass systems more steeply than the fgas decrease with total mass. Adding the gas and stellar mass fractions to obtain the total baryonic content, we find it to increase with cluster mass, reaching the WMAP-7 value for clusters with M500 ~ 1014 M⊙. This led us to investigate the contribution of the intracluster light to the total baryon budget for lower mass systems, but we find that it cannot account for the difference observed. Conclusions. The gas mass fraction dependence on total mass observed for groups and clusters could be due to the difficulty of low-mass systems to retain gas inside the inner region (r < r2500). Because of their shallower potential well, non-thermal processes are more effective in expelling the gas from their central regions outwards. Since the differential gas mass fraction is nearly constant, it provides better constraints for cosmology. Moreover, we find that the gas mass fraction does not depend on redshift at a 2σ level. Using our total fb estimates, our results imply Ωm < 0.55, and taking the highest significant estimates for fb, Ωm > 0.22.
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