Volume 630, October 2019
|Number of page(s)||10|
|Section||Cosmology (including clusters of galaxies)|
|Published online||03 October 2019|
Spectral imaging of the thermal Sunyaev–Zel’dovich effect in X-COP galaxy clusters: method and validation
Università di Roma “Tor Vergata”, Via della Ricerca Scientifica, 00133 Roma, Italy
2 Sapienza Università di Roma, Piazzale Aldo Moro 5, 00085 Roma, Italy
3 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
4 INAF, Osservatorio di Astrofisica e Scienza dello Spazio, Via Pietro Gobetti 93/3, 40129 Bologna, Italy
5 INFN, Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
6 Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544-1001, USA
7 Dipartimento di Fisica e Astronomia, Université di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
Accepted: 27 August 2019
The imaging of galaxy clusters through the Sunyaev–Zel’dovich effect is a valuable tool to probe the thermal pressure of the intra-cluster gas, especially in the outermost regions where X-ray observations suffer from photon statistics. For the first time, we produce maps of the Comptonization parameter by applying a locally parametric algorithm for sparse component separation to the latest frequency maps released by Planck. The algorithm takes into account properties of real cluster data through the two-component modelling of the spectral energy density of thermal dust, and the masking of bright point sources. Its robustness has been improved in the low signal-to-noise regime, thanks to the implementation of a deconvolution of Planck beams in the chi-square minimisation of each wavelet coefficient. We applied this procedure to twelve low-redshift galaxy clusters detected by Planck with the highest signal-to-noise ratio, considered in the XMM Cluster Oustkirts Project (X-COP). Our images show the presence of anisotropic features, such as small-scale blobs and filamentary substructures that are located in the outskirts of a number of clusters in the sample. The significance of their detection is established via a bootstrap-based procedure we propose here for the first time. In particular, we present a qualitative comparison with X-ray data for two interesting systems, namely A2029 and RXCJ1825. Our results are in agreement with the features detected in the outskirts of the clusters in the two bands.
Key words: techniques: image processing / galaxies: clusters: general / galaxies: clusters: intracluster medium
© ESO 2019
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