Astrophys. J., 843, 76-76 (2017/July-1)
The fraction of cool-core clusters in X-ray versus SZ samples using Chandra observations.
ANDRADE-SANTOS F., JONES C., FORMAN W.R., LOVISARI L., VIKHLININ A., VAN WEEREN R.J., MURRAY S.S., ARNAUD M., PRATT G.W., DEMOCLES J., KRAFT R., MAZZOTTA P., BOHRINGER H., CHON G., GIACINTUCCI S., CLARKE T.E., BORGANI S., DAVID L., DOUSPIS M., POINTECOUTEAU E., DAHLE H., BROWN S., AGHANIM N. and RASIA E.
Abstract (from CDS):
We derive and compare the fractions of cool-core clusters in the Planck Early Sunyaev-Zel'dovich sample of 164 clusters with z 0.35 and in a flux-limited X-ray sample of 100 clusters with z 0.30, using Chandra observations. We use four metrics to identify cool-core clusters: (1) the concentration parameter, which is the ratio of the integrated emissivity profile within 0.15 r500 to that within r500; (2) the ratio of the integrated emissivity profile within 40 kpc to that within 400 kpc; (3) the cuspiness of the gas density profile, which is the negative of the logarithmic derivative of the gas density with respect to the radius, measured at 0.04 r500; and (4) the central gas density, measured at 0.01 r500. We find that the sample of X-ray-selected clusters, as characterized by each of these metrics, contains a significantly larger fraction of cool-core clusters compared to the sample of SZ-selected clusters (44% ± 7% versus 28% ± 4% using the concentration parameter in the 0.15-1.0 r500 range, 61% ± 8% versus 36% ± 5% using the concentration parameter in the 40-400 kpc range, 64% ± 8% versus 38% ± 5% using the cuspiness, and 53% ± 7% versus 39 ± 5% using the central gas density). Qualitatively, cool-core clusters are more X-ray luminous at fixed mass. Hence, our X-ray, flux-limited sample, compared to the approximately mass-limited SZ sample, is overrepresented with cool-core clusters. We describe a simple quantitative model that uses the excess luminosity of cool-core clusters compared to non-cool-core clusters at fixed mass to successfully predict the observed fraction of cool-core clusters in X-ray-selected samples.
© 2017. The American Astronomical Society. All rights reserved.
galaxies: clusters: general - large-structure of universe - large-structure of universe
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<Available at CDS (J/ApJ/843/76): table4.dat table5.dat>
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