Yu-Ying Zhang

A weak lensing study of X-ray groups in the cosmos survey: form and evolution of the mass-luminosity relation

Measurements of X-ray scaling laws are critical for improving cosmological constraints derived with the halo mass function and for understanding the physical processes that govern the heating and cooling of the intracluster medium. In this paper, we use a sample of 206 X-ray-selected galaxy groups to investigate the scaling relation between X-ray luminosity (L_X) and halo mass (M_(200)) where M_(200) is derived via stacked weak gravitational lensing. This work draws upon a broad array of multi-wavelength COSMOS observations including 1.64 degrees^2 of contiguous imaging with the Advanced Camera for Surveys to a limiting magnitude of I_(F814W) = 26.5 and deep XMM-Newton/Chandra imaging to a limiting flux of 1.0 × 10^(–15) erg cm6(–2) s^(–1) in the 0.5-2 keV band. The combined depth of these two data sets allows us to probe the lensing signals of X-ray-detected structures at both higher redshifts and lower masses than previously explored. Weak lensing profiles and halo masses are derived for nine sub-samples, narrowly binned in luminosity and redshift. The COSMOS data alone are well fit by a power law, M_(200) (L_X)^α, with a slope of α = 0.66 ± 0.14. These results significantly extend the dynamic range for which the halo masses of X-ray-selected structures have been measured with weak gravitational lensing. As a result, tight constraints are obtained for the slope of the M-L_X relation. The combination of our group data with previously published cluster data demonstrates that the M-L_X relation is well described by a single power law, α = 0.64 ± 0.03, over two decades in mass, M_(200) ~ 10^(13.5)-10^(15.5) h^(–1)_72 M_☉. These results are inconsistent at the 3.7σ level with the self-similar prediction of α = 0.75. We examine the redshift dependence of the M-L_X relation and find little evidence for evolution beyond the rate predicted by self-similarity from z ~ 0.25 to z ~ 0.

Statistics of X-ray observables for the cooling-core and non-cooling core galaxy clusters

We present a statistical study of the occurrence and effects of the cooling cores in the clusters of galaxies in a flux-limited sample, HIFLUGCS, based on ROSAT and ASCA observations. About 49% of the clusters in this sample have a significant, classically-calculated cooling-flow, mass-deposition rate. The upper envelope of the derived mass-deposition rate is roughly proportional to the cluster mass, and the fraction of cooling core clusters is found to decrease with it. The cooling core clusters are found to have smaller core radii than non-cooling core clusters, while some non-cooling core clusters have high beta values (> 0.8). In the relation of the X-ray luminosity vs. the temperature and the mass, the cooling core clusters show a significantly higher normalization. A systematic correlation analysis, also involving relations of the gas mass and the total infrared luminosity, indicates that this bias is shown to be mostly due to an enhanced X-ray luminosity for cooling core clusters, while the other parameters, like temperature, mass, and gas mass may be less affected by the occurrence of a cooling core. These results may be explained by at least some of the non-cooling core clusters being in dynamically young states compared with cooling core clusters, and they may turn into cooling core clusters in a later evolutionary stage.

The Representative XMM-Newton Cluster Structure Survey (REXCESS) of an X-ray Luminosity Selected Galaxy Cluster Sample

Context.The largest uncertainty for cosmological studies using clusters of galaxies is introduced by our limited knowledge of the statistics of galaxy cluster structure, and of the scaling relations between observables and cluster mass.

X-ray properties in massive galaxy clusters: XMM-Newton observations of the REFLEX-DXL sample

We selected an unbiased, flux-limited and almost volume-com plete sample of 13 distant, X-ray luminous (DXL, z ∼ 0.3) clusters and one supplementary cluster at z = 0.2578 from the REFLEX Survey (the REFLEX-DXL sample). We performed a detailed study to explore their X-ray properties using XMM-Newton observations. Based on the precise radial distributions of the gas density and temperature, we obtained robust cluster masses and gas mass fractions. The average gas mass fraction of the REFLEX-DXL sample at r500, 0.116± 0.007, agrees with the previous cluster studies and the WMAP baryon fraction measurement. The scaled profiles of the surf ace brightness, temperature, entropy, gas mass and total mass are characterized by a self-similar behaviour at radii above 0. 2-0.3 r500. The REFLEX-DXL sample confirms the previous studies of the normalization of the scaling relations ( L-T , L-M, M-T and Mgas-T ) when the redshift evolution of the scaling relations is accounted for. We investigated the scatter of the scaling relations of the REFLEX-DXL sample. This gives the correlative scatter of (0.20,0.10) for variable of ( M,T ) of the M500-T relation, for example.

LoCuSS: calibrating mass-observable scaling relations for cluster cosmology with Subaru weak-lensing observations

N.O., M.T., and T.F. are supported in part by a Grant-in-Aid from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (N.O.: 20740099; M.T.: 20740119; T.F.: 20540245). Y.-Y.Z. and N.O. acknowledge support by the DFG through the Emmy Noether Research Grant RE 1462/2, through Schwerpunkt Program 1177, and through project B6 “Gravitational Lensing and X-ray Emission by Non-Linear Structures” of Transregional Collaborative Research Centre TRR 33 “The Dark Universe,” and support by the German BMBF through the Verbundforschung under grants 50 OR 0601 and 50 OR 1005. A.F. acknowledges support from BMBF/DLR under grant 50 OR 0207 and MPG. A.F. was partially supported by NASA grant NNX08AX46G to UMBC. K.U. is partially supported by the National Science Council of Taiwan under the grant NSC95-2112-M-001-074-MY2. G.P.S. acknowledges support from the Royal Society. This work is supported by a Grant-in-Aid for the COE Program “Exploring NewScience by Bridging Particle–MatterHierarchy” and theGCOE Program “Weaving Science Web beyond Particle–Matter Hierarchy” in Tohoku University, funded by the Ministry of Education, Science, Sports and Culture of Japan. This work is in part supported by a Grant-in-Aid for Science Research in a Priority Area “Probing the Dark Energy through an Extremely Wide and Deep Survey with Subaru Telescope” (18072001) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. Y.-Y.Z. and A.F. acknowledge the hospitality of the Tohoku University during their frequent visits. This work is supported in part by the World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan.

Scaling relations and mass calibration of the X-ray luminous galaxy clusters at redshift ~0.2: XMM-Newton observations

We present the X-ray properties and scaling relations of a flux-limited morphology-unbiased sample of 12 X-ray luminous galaxy clusters at redshift around 0.2 based on XMM-Newton observations. The scaled radial profiles are characterized by a self-similar behavior at radii outside the cluster cores (> 0.2 r_(500)) for the temperature (T ∝ r^(−0.36)), surface brightness, entropy (S ∝ r^(1.01)), gas mass and total mass. The cluster cores contribute up to 70% of the bolometric X-ray luminosity. The X-ray scaling relations and their scatter are sensitive to the presence of the cool cores. Using the X-ray luminosity corrected for the cluster central region and the temperature measured excluding the cluster central region, the normalization agrees to better than 10% for the cool core clusters and non-cool core clusters, irrelevant to the cluster morphology. No evolution of the X-ray scaling relations was observed comparing this sample to the nearby and more distant samples. With the current observations, the cluster temperature and luminosity can be used as reliable mass indicators with the mass scatter within 20%. Mass discrepancies remain between X-ray and lensing and lead to larger scatter in the scaling relations using the lensing masses (e.g. ~40% for the luminosity-mass relation) than using the X-ray masses (<20%) due to the possible reasons discussed.

Temperature gradients in XMM-Newton observed REFLEX-DXL galaxy clusters at z - 0.3

We present XMM-Newton results on the temperature profiles of a volume-limited sample of galaxy clusters at redshifts z ∼ 0.3, selected from the REFLEX survey (REFLEX-DXL sample). In the spectral analysis, where only the energies above I keV were considered, we obtained consistent results for the temperature derived from the pn, MOS1 and MOS2 data. Useful temperature measurements could be performed out to radii with overdensity 500 (r 5 0 0 ) for all nine clusters. We discovered a diversity in the temperature gradients at the outer cluster radii with examples of both flat and strongly decreasing profiles. Using the total mass and the gas mass profiles for the cluster RXCJ0307.0-2840 we demonstrate that the errors on the mass estimates for the REFLEX-DXL clusters are within 25% up to r 5 0 0 .

X-ray substructure studies of four galaxy clusters using XMM-Newton data

Mahdavi et al. find that the degree of agreement between weak lensing and X-ray mass measurements is a function of cluster radius. Numerical simulations also point out that X-ray mass proxies do not work equally well at all radii. The origin of the effect is thought to be associated with cluster mergers. Recent work presenting the cluster maps showed an ability of X-ray maps to reveal and study cluster mergers in detail. Here, we present a first attempt to use the study of substructure in assessing the systematics of the hydrostatic mass measurements using two-dimensional (2D) X-ray diagnostics. The temperature map is uniquely able to identify the substructure in an almost relaxed cluster which would be unnoticed in the intracluster medium electron number density and pressure maps. We describe the radial fluctuations in the 2D maps by a cumulative/differential scatter profile relative to the mean profile within/at a given radius. The amplitude indicates ~10% fluctuations in the temperature, electron number density, and entropy maps, and ~15% fluctuations in the pressure map. The amplitude of and the discontinuity in the scatter complement 2D substructure diagnostics, e.g., indicating the most disturbed radial range. There is a tantalizing link between the substructure identified using the scatter of the entropy and pressure fluctuations and the hydrostatic mass bias relative to the expected mass based on the M-Y X and M-M gas relations particularly at r 500. XMM-Newton observations with ~120,000 source photons from the cluster are sufficient to apply our substructure diagnostics via the spectrally measured 2D temperature, electron number density, entropy, and pressure maps.

XMM-Newton study of the lensing cluster of galaxies CL 0024+17

We present a detailed gravitational mass measurement based on the XMM-Newton imaging spectroscopy analysis of the lensing cluster of galaxies CL 0024+17 at z = 0.395. The emission appears approximately symmetric. However, on the scale of r ∼ 3.3 � some indication of elongation is visible in the northwest-southeast (NW-SE) direction from the hardness ratio map (HRM). Within 3 � , we measure a global gas temperature of 3.52 ± 0.17 keV, metallicity of 0.22 ± 0.07, and bolometric luminosity of 2.9 ± 0.1 × 10 44 h −2 70 erg s −1 . We derive a temperature distribution with an isothermal temperature of 3.9 keV to a radius of 1.5 � and a temperature gradient in the outskirts (1.3 � < r < 3 � ). Under the assumption of hydrostatic equilibrium, we measure gravitational mass and gas mass fraction to be M200 = 2.0 ± 0.3 × 10 14 h −1 70 Mand fgas = 0.20 ± 0.03 h −3/2 70 at r200 = 1.05 h −1 70 Mpc using the observed temperature profile. The complex structure in the core region is the key to explaining the discrepancy in gravitational mass determined from XMM-Newton X-ray observations and HST optical lensing measurements.

Chemical Enrichment RGS cluster Sample (CHEERS): Constraints on turbulence

Context. Feedback from active galactic nuclei, galactic mergers, and sloshing are thought to give rise to turbulence, which may prevent cooling in clusters. Aims. We aim to measure the turbulence in clusters of galaxies and compare the measurements to some of their structural and evolutionary properties. Methods. It is possible to measure the turbulence of the hot gas in clus ters by estimating the velocity widths of their X-ray emissi on lines. The Reflection Grating Spectrometers aboard XMM- Newton are currently the only instruments provided with suffi cient effective area and spectral resolution in this energy domain. We benefi ted from excellent 1.6 Ms new data provided by the Chemical Enrichment RGS cluster sample (CHEERS) project. Results. The new observations improve the quality of the archival data and allow us to place constraints for some clusters, which were not accessible in previous work. One-half of the sample shows upper limits on turbulence less than 500 km s −1 . For several sources, our data are consistent with relatively strong turbulence w ith upper limits on the velocity widths that are larger than 1 000 km s −1 . The NGC 507 group of galaxies shows transonic velocities, which are most likely associated with the merging phenomena and bulk motions occurring in this object. Where both low- and high-ionization emission lines have good enough statistics, we fin d larger upper limits for the hot gas, which is partly due to the different spatial extents of the hot and cool gas phases. Our upper limits are larger than the Mach numbers required to balance cooling, suggesting that dissipation of turbulence may prevent cooling, although other heating processes could be dominant. The systematics associated with the spatial profile of the source continuum make th is technique very challenging, though still powerful, for current instr uments. In a forthcoming paper we will use the resonant-scattering technique to place lower-limits on the velocity broadening and provide further insights on turbulence. The ASTRO-H and Athena missions will revolutionize the velocity estimates and discriminate bet ween different spatial regions and temperature phases.