The Fraction of Cool-core Clusters in X-Ray versus SZ Samples Using Chandra Observations

Journal
Date Issued
2017
Author(s)
Andrade-Santos, Felipe
•
Jones, Christine
•
Forman, William R.
•
•
Vikhlinin, Alexey
•
van Weeren, Reinout J.
•
Murray, Stephen S.
•
Arnaud, Monique
•
Pratt, Gabriel W.
•
Démoclès, Jessica
•
Kraft, Ralph
•
•
Böhringer, Hans
•
Chon, Gayoung
•
Giacintucci, Simona
•
Clarke, Tracy E.
•
•
David, Larry
•
Douspis, Marian
•
Pointecouteau, Etienne
•
Dahle, Håkon
•
Brown, Shea
•
Aghanim, Nabila
•
DOI
Abstract
We derive and compare the fractions of cool-core clusters in the Planck Early Sunyaev-Zel’dovich sample of 164 clusters with z≤slant 0.35 and in a flux-limited X-ray sample of 100 clusters with z≤slant 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 r 500 to that within r 500; (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 r 500; and (4) the central gas density, measured at 0.01 r 500. 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 r 500 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.
Volume
843
Issue
1
Start page
76
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2017ApJ...843...76A
Rights
open.access
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