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• Paper pool
  • Mass Calibration of Galaxy Clusters at Redshift 0.1-1.0 using Weak Lensing in the Sloan Digital Sky Survey Stripe 82 Co-add
  • The physics inside the scaling relations for X-ray galaxy clusters: gas clumpiness, gas mass fraction and slope of the pressure profile
  • A Simple Physical Model for the Gas Distribution in Galaxy Clusters
  • Brightest X-ray clusters of galaxies in the CFHTLS wide fields: Catalog and optical mass estimator
  • Deconstructing Thermal Sunyaev-Zel'dovich - Gravitational Lensing Cross-Correlations: Implications for the Intracluster Medium
  • Dissecting the thermal Sunyaev-Zeldovich-gravitational lensing cross-correlation with hydrodynamical simulations

Mass Calibration of Galaxy Clusters at Redshift 0.1-1.0 using Weak Lensing in the Sloan Digital Sky Survey Stripe 82 Co-add¶

Matthew P. Wiesner, Huan Lin, Marcelle Soares-Santos

We present mass-richness relations found in the Sloan Digital Sky Survey Stripe 82 co-add. These relations were found using stacked weak lensing shear observed in a large sample of galaxy clusters. These mass-richness relations are presented for four redshift bins, 0.1<z≤0.4, 0.4<z≤0.7, 0.7<z≤1.0 and 0.1<z≤1.0. We describe the sample of galaxy clusters and explain how these clusters were found using a Voronoi Tessellation cluster finder. We fit an NFW profile to the stacked weak lensing shear signal in redshift and richness bins in order to measure virial mass (M200). We describe several effects that can bias weak lensing measurements, including photometric redshift bias, the effect of the central BCG, halo miscentering, photometric redshift uncertainty and foreground galaxy contamination. We present mass-richness relations using richness measure NVT with each of these effects considered separately as well as considered altogether. We present values for the mass coefficient (M200|20) and the power law slope (α) for power law fits to the mass and richness values in each of the redshift bins. We find values of the mass coefficient of 8.30±0.682, 13.8±1.94, 27.3±14.7 and 8.61±0.719×1013h−1Msun for each of the four redshift bins respectively. We find values of the power law slope of 0.988±0.0716, 0.962±0.130, 1.52±0.483 and 1.01±0.0803 respectively. Finally, we examine redshift evolution of the mass-richness relation.

The physics inside the scaling relations for X-ray galaxy clusters: gas clumpiness, gas mass fraction and slope of the pressure profile¶

S. Ettori (INAF-OA Bologna)

In galaxy clusters, the relations between observables in X-ray and millimeter wave bands and the total mass have normalizations, slopes and redshift evolutions that are simple to estimate in a self-similar scenario. We study these scaling relations and show that they can be efficiently expressed, in a more coherent picture, by fixing the normalizations and slopes to the self-similar predictions, and advocating, as responsible of the observed deviations, only three physical mass-dependent quantities: the gas clumpiness $C$, the gas mass fraction $f_g$ and the logarithmic slope of the thermal pressure profile $\beta_P$. We use samples of the observed gas masses, temperature, luminosities, and Compton parameters in local clusters to constrain normalization and mass dependence of these 3 physical quantities, and measure: $C^{0.5} f_g = 0.110 (\pm 0.002 \pm 0.002) \left( E_z M / 5 \times 10^{14} M_{\odot} \right)^{0.198 (\pm 0.025 \pm 0.04)}$ and $\beta_P = -d \ln P/d \ln r = 3.14 (\pm 0.04 \pm 0.02) \left( E_z M / 5 \times 10^{14} M_{\odot} \right)^{0.071 (\pm 0.012 \pm 0.004)}$, where both a statistical and systematic error (the latter mainly due to the cross-calibration uncertainties affecting the \cxo\ and \xmm\ results used in the present analysis) are quoted. The degeneracy between $C$ and $f_g$ is broken by using the estimates of the Compton parameters. Together with the self-similar predictions, these estimates on $C$, $f_g$ and $\beta_P$ define an inter-correlated internally-consistent set of scaling relations that reproduces the mass estimates with the lowest residuals.

A Simple Physical Model for the Gas Distribution in Galaxy Clusters¶

Anna Patej, Abraham Loeb

The dominant baryonic component of galaxy clusters is hot gas whose distribution is commonly probed through X-ray emission arising from thermal bremsstrahlung. The density profile thus obtained has been traditionally modeled with a beta-profile, a simple function with only three parameters. However, this model is known to be insufficient for characterizing the range of cluster gas distributions, and attempts to rectify this shortcoming typically introduce additional parameters to increase the fitting flexibility. We use cosmological and physical considerations to obtain a family of profiles for the gas with fewer parameters than the beta-model but which better accounts for observed gas profiles over wide radial intervals.

Brightest X-ray clusters of galaxies in the CFHTLS wide fields: Catalog and optical mass estimator¶

M. Mirkazemi, A. Finoguenov, M. J. Pereira, M. Tanaka, M. Lerchster, F. Brimioulle, E. Egami, K. Kettula, G. Erfanianfar, H. J. McCracken, Y. Mellier, J. P. Kneib, E. Rykoff, S. Seitz, T. Erben, J. E. Taylor

The CFHTLS presents a unique data set for weak lensing studies, having high quality imaging and deep multi-band photometry. We have initiated an XMM-CFHTLS project to provide X-ray observations of the brightest X-ray selected clusters within the wide CFHTLS area. Performance of these observations and the high quality of CFHTLS data, allows us to revisit the identification of X-ray sources, introducing automated reproducible algorithms, based on the multi-color red sequence finder. We have also introduced a new optical mass proxy. We provide the calibration of the red sequence observed in the CFHT filters and compare the results with the traditional single color red sequence and photoz. We test the identification algorithm on the subset of highly significant XMM clusters and identify 100% of the sample. We find that the integrated z-band luminosity of the red sequence galaxies correlates well with the X-ray luminosity with a surprisingly small scatter of 0.20 dex. We further use the multi-color red sequence to reduce spurious detections in the full XMM and RASS data sets, resulting in catalogs of 196 and 32 clusters, respectively. We made spectroscopic follow-up observations of some of these systems with HECTOSPEC and in combination with BOSS DR9 data. We also describe the modifications needed to the source detection algorithm in order to keep high purity of extended sources in the shallow X-ray data. We also present the scaling relation between X-ray luminosity and velocity dispersion.

Deconstructing Thermal Sunyaev-Zel'dovich - Gravitational Lensing Cross-Correlations: Implications for the Intracluster Medium¶

N. Battaglia (Princeton), J. C. Hill (Columbia), N. Murray (CITA)

Recent first detections of the cross-correlation of the thermal Sunyaev-Zel'dovich (tSZ) signal in Planck cosmic microwave background (CMB) temperature maps with gravitational lensing maps inferred from the Planck CMB data and the CFHTLenS galaxy survey provide new probes of the relationship between baryons and dark matter. Using cosmological hydrodynamics simulations, we show that these cross-correlation signals are dominated by contributions from hot gas in the intracluster medium (ICM), rather than diffuse, unbound gas located beyond the virial radius (the "missing baryons"). Thus, these cross-correlations offer a tool with which to study the ICM over a wide range of halo masses and redshifts. In particular, we show that the tSZ - CMB lensing cross-correlation is more sensitive to gas in lower-mass, higher-redshift halos and gas at larger cluster-centric radii than the tSZ - galaxy lensing cross-correlation. Combining these measurements with primary CMB data will constrain feedback models through their signatures in the ICM pressure profile. We forecast the ability of ongoing and future experiments to constrain such ICM parameters, including the mean amplitude of the pressure - mass relation, the redshift evolution of this amplitude, and the mean outer logarithmic slope of the pressure profile. The results are promising, with ≈5−20% precision constraints achievable with upcoming experiments, even after marginalizing over cosmological parameters.

Dissecting the thermal Sunyaev-Zeldovich-gravitational lensing cross-correlation with hydrodynamical simulations¶

Alireza Hojjati, Ian G. McCarthy, Joachim Harnois-Deraps, Yin-Zhe Ma, Ludovic Van Waerbeke, Gary Hinshaw, Amandine M. C. Le Brun

We use the cosmo-OWLS suite of cosmological hydrodynamical simulations, which includes different galactic feedback models, to predict the cross-correlation signal between weak gravitational lensing and the thermal Sunyaev-Zeldovich (tSZ) y-parameter. The predictions are compared to the recent detection reported by van Waerbeke and collaborators. The simulations reproduce the weak lensing-tSZ cross-correlation, ξyκ(θ), well. The uncertainty arising from different possible feedback models appears to be important on small scales only (θ≲10 arcmin), while the amplitude of the correlation on all scales is sensitive to cosmological parameters that control the growth rate of structure (such as σ8, Ωm and Ωb). This study confirms our previous claim (in Ma et al.) that a significant proportion of the signal originates from the diffuse gas component in low-mass (Mhalo≲1014M⊙) clusters as well as from the region beyond the virial radius. We estimate that approximately 20% of the detected signal comes from low-mass clusters, which corresponds to about 30% of the baryon density of the Universe. The simulations also suggest that more than half of the baryons in the Universe are in the form of diffuse gas outside halos (≳5 times the virial radius) which is not hot or dense enough to produce a significant tSZ signal or be observed by X-ray experiments. Finally, we show that future high-resolution tSZ-lensing cross-correlation observations will serve as a powerful tool for discriminating between different galactic feedback models.