The Redshift Evolution of the Mean Temperature, Pressure, and Entropy Profiles in 80 SPT-Selected Galaxy Clusters

Abstract

We present the results of an X-ray analysis of 80 galaxy clusters selected in the 2500 deg 2 South Pole Telescope survey and observed with the Chandra X-ray Observatory. We divide the full sample into subsamples of ∼20 clusters based on redshift and central density, performing a joint X-ray spectral fit to all clusters in a subsample simultaneously, assuming self-similarity of the temperature profile. This approach allows us to constrain the shape of the temperature profile over 0 < r < 1.5R 500 , which would be impossible on a per-cluster basis, since the observations of individual clusters have, on average, 2000 X-ray counts. The results presented here represent the first constraints on the evolution of the average temperature profile from z = 0 to z = 1.2. We find that high-z (0.6 < z < 1.2) clusters are slightly (∼30%) cooler both in the inner (r < 0.1R 500 ) and outer (r > R 500 ) regions than their low-z (0.3 < z < 0.6) counterparts. Combining the average temperature profile with measured gas density profiles from our earlier work, we infer the average pressure and entropy profiles for each subsample. Confirming earlier results from this data set, we find an absence of strong cool cores at high z, manifested in this analysis as a significantly lower observed pressure in the central 0.1R 500 of the high-z cool-core subset of clusters compared to the low-z cool-core subset. Overall, our observed pressure profiles agree well with earlier lower-redshift measurements, suggesting minimal redshift evolution in the pressure profile outside of the core. We find no measurable redshift evolution in the entropy profile at r 0.7R 500 -this may reflect a long-standing balance between cooling and feedback over long timescales and large physical scales. We observe a slight flattening of the entropy profile at r R 500 in our high-z subsample. This flattening is consistent with a temperature bias due to the enhanced (∼3×) rate at which group-mass (∼2 keV) halos, which would go undetected at our survey depth, are accreting onto the cluster at z ∼ 1. This work demonstrates a powerful method for inferring spatially resolved cluster properties in the case where individual cluster signal-to-noise is low, but the number of observed clusters is high.

SZ effects in the Magneticum Pathfinder simulation: comparison with thePlanck, SPT, and ACT results

“…Azimuthally-averaged radial profiles of thermal pressure in galaxy clusters identified in our hydrodynamical simulations follow the so-called "universe pressure profile" (Arnaud et al 2010a). The stacked pressure profiles of galaxy-cluster-size halos in our simulation are in good agreement with the stacked pressure profiles inferred from the tSZ data on galaxy clusters detected by Planck (Planck Collaboration et al 2013a) and South Pole Telescope (SPT) (McDonald et al 2014). However, such comparisons allow only a statistical comparison of the averaged profiles.…”

STAR-FORMING BRIGHTEST CLUSTER GALAXIES AT 0.25 < z < 1.25: A TRANSITIONING FUEL SUPPLY

“…Given that we only have ∼2000 X-ray counts per cluster, modeling the central entropy (e.g., Cavagnolo et al 2009) or estimating the spectroscopically derived cooling rate (e.g., Voigt & Fabian 2004) is not feasible. Instead, we compute spectroscopic quantities (bolometric luminosity, temperature) from a circular aperture with a radius of 0.075 R 500 (where R 500 was derived based on the Y X -M 500 relation of Vikhlinin et al 2009), which should roughly correspond to the deprojected core temperature (see e.g., McDonald et al 2014a). X-ray spectra extracted from this aperture are modeled with a photometric absorption (PHABS) and plasma (APEC) model, allowing the temperature, metallicity, and normalization of the plasma model to vary.…”

“…We discuss the effects of this choice in later sections. For a more detailed description of our X-ray analysis techniques, we direct the reader to McDonald et al (2013bMcDonald et al ( , 2014a.…”

Pressure distribution of the high-redshift cluster of galaxies CL J1226.9+3332 with NIKA

“…In addition we notice that our error bars are model dependent and do not reflect the full uncertainty of the data. The evolution of the pressure profile with redshift has been statistically tested recently using a Chandra X-ray analysis of 80 SPT clusters (McDonald et al 2014) with a highest bin at a mean redshift z = 0.82. They find no significant evolution, apart from the cluster's cores, and agree with a standard redshift evolution of the pressure distribution among clusters.…”