Journal Article

Signature of cool core in Sunyaev–Zeldovich clusters: a multiwavelength approach

A. Pipino and E. Pierpaoli

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 404, issue 3, pages 1603-1616
Published in print May 2010 | ISSN: 0035-8711
Published online May 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16393.x
Signature of cool core in Sunyaev–Zeldovich clusters: a multiwavelength approach

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We use the high quality pressure profiles of 239 galaxy clusters made available by the Archive of Chandra Cluster Entropy Profile Tables (ACCEPT) project in order to derive the expected Sunyaev–Zeldovich (SZ) signal in a variety of cases that hardly find a counterpart in the simulations. We made use of the Melin et al. cluster selection function for both the South Pole Telescope (SPT) and Planck instruments. Prior knowledge of the entropy profiles of the same clusters allows us to study the impact of cool cores (CC) in cluster detection via SZ experiment and to test if this introduces a bias in inferred quantities as e.g. the mass function.

We infer a clear effect of the CC on the central Compton parameter y0. We thus validate the suggestions by McCarthy et al., namely that at a given mass clusters with higher entropy levels show a lower y0 than their low-entropy counterparts, on a much larger sample of clusters. For a high-resolution experiment like SPT, we expect that the fraction of detected clusters with respect to the total to decline at masses around ∼2 × 1014 M. For Planck this happens at a somewhat higher mass. We find that the presence of CCs introduces a small bias in cluster detection, especially around the mass at which the performance of the survey begins to decrease. If the CC were removed, a lower overall fraction of detected clusters would be expected. In order to estimate the presence of such a bias by means of SZ-only surveys, we show that the ratio between y0 and yint anticorrelates with the cluster central cooling time. If multiband optical cluster surveys are either available for a cross-match or a follow-up is planned, we suggest that likely CC clusters are those with a brightest cluster galaxy (BCG) at least 0.3 mag bluer than the average. A more robust estimate of the CC presence is given by UV–optical colours of the BCG, like the NUV-r, whose values can be 4 mag off the NUV-r equivalent of the red sequence, in clusters with low excess entropy. We also find correlation of the y0/yint ratio with Hα, IR and radio luminosities. We argue that the analysis of a combined SZ/optical/UV surveys can be also used to shed light on the suggested CC evolution with redshift.

Keywords: galaxies: clusters: general; cooling flows; galaxies: elliptical and lenticular, cD; galaxies: evolution; X-rays: galaxies: clusters

Journal Article.  11447 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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