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Detailed Sunyaev–Zel’dovich study with AMI of 19 LoCuSS galaxy clusters: masses and temperatures out to the virial radius

Rodríguez-Gonzálvez, Carmen and Shimwell, Timothy W. and Davies, Matthew L. and Feroz, Farhan and Franzen, Thomas M. O. and Grainge, Keith J. B. and Hobson, Michael P. and Hurley-Walker, Natasha and Lasenby, Anthony N. and Olamaie, Malak and Pooley, Guy and Saunders, Richard D. E. and Scaife, Anna M. M. and Schammel, Michel P. and Scott, Paul F. and Titterington, David J. and Waldram, Elizabeth M. (2012) Detailed Sunyaev–Zel’dovich study with AMI of 19 LoCuSS galaxy clusters: masses and temperatures out to the virial radius. Monthly Notices of the Royal Astronomical Society, 425 (1). pp. 162-203. ISSN 0035-8711.

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We present detailed 16-GHz interferometric observations using the Arcminute Microkelvin Imager (AMI) of 19 clusters with L_X > 7 × 10^(37) W (h_(50) = 1) selected from the Local Cluster Substructure Survey (LoCuSS; 0.142 ≤ z ≤ 0.295) and of Abell 1758b, which is in the field of view of Abell 1758a. We detect and resolve Sunyaev–Zel'dovich (SZ) signals towards 17 clusters, with peak surface brightnesses between 5σ and 23σ. We use a fast, Bayesian cluster analysis to obtain cluster parameter estimates in the presence of radio point sources, receiver noise and primordial cosmic microwave background (CMB) anisotropy. We fit isothermal β-models to our data and assume the clusters are virialized (with all the kinetic energy in gas internal energy). Our gas temperature, T_(AMI), is derived from AMI SZ data and not from X-ray spectroscopy. Cluster parameters internal to r_(500) are derived under the assumption of hydrostatic equilibrium. We find the following. (i) Different generalized Navarro–Frenk–White (gNFW) parametrizations yield significantly different parameter degeneracies. (ii) For h_(70) = 1, we find the classical virial radius, r_(200), to be typically 1.6 ± 0.1 Mpc and the total mass M_T(r_(200)) typically to be 2.0–2.5× M_T(r_(500)). (iii) Where we have found M_T(r_(500)) and M_T(r_(200)) X-ray and weak-lensing values in the literature, there is good agreement between weak-lensing and AMI estimates (with M_(T,AMI)/M_(T,WL) = 1.2^(+0.2)_(−0.3) and 1.0 ± 0.1 for r_(500) and r_(200), respectively). In comparison, most Suzaku/Chandra estimates are higher than for AMI (with M_(T,X)/M_(T,AMI) = 1.7 ± 0.2 within r_(500)), particularly for the stronger mergers. (iv) Comparison of T_(AMI) to T_X sheds light on high X-ray masses: even at large radius, T_X can substantially exceed T_(AMI) in mergers. The use of these higher T_X values will give higher X-ray masses. We stress that large-radius T_(AMI) and T_X data are scarce and must be increased. (v) Despite the paucity of data, there is an indication of a relation between merger activity and SZ ellipticity. (vi) At small radius (but away from any cooling flow) the SZ signal (and T_(AMI)) is less sensitive to intracluster medium disturbance than the X-ray signal (and T_X) and, even at high radius, mergers affect n^2-weighted X-ray data more than n-weighted SZ, implying that significant shocking or clumping or both occur in even the outer parts of mergers.

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Hurley-Walker, Natasha0000-0002-5119-4808
Additional Information:© 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS. Accepted 2012 May 30. Received 2012 May 25; in original form 2011 January 28. Article first published online: 2 Aug 2012. We thank an anonymous referee for very quick and helpful comments and suggestions, and Alastair Edge for helpful discussion. We are grateful to the staff of the Cavendish Laboratory and the Mullard Radio Astronomy Observatory for the maintenance and operation of AMI. We acknowledge support from Cambridge University and STFC for funding and supporting AMI. MLD, TMOF, MO, CRG, MPS and TWS are grateful for support from STFC studentships. This work was carried out using the Darwin Supercomputer of Cambridge University High Performance Computing Service (, provided by Dell Inc. using Strategic Research Infrastructure Funding from the Higher Education Funding Council for England and theAltix 3700 supercomputer at DAMTP, Cambridge University, supported by HEFCE and STFC. We thank Stuart Rankin and Andrey Kaliazin for their computing support. This research has made use of data from the Chandra Data Archive (ACCEPT) (Cavagnolo et al. 2000).We acknowledge the use of NASA’s Sky View facility ( located at NASA Goddard Space Flight Center.
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Cambridge UniversityUNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Higher Education Funding Council for EnglandUNSPECIFIED
Subject Keywords: methods: observational; techniques: interferometric; galaxies: clusters: general; galaxies: clusters: intracluster medium; cosmic background radiation; large-scale structure of Universe
Issue or Number:1
Record Number:CaltechAUTHORS:20121009-114029294
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Official Citation:AMI Consortium:, Rodríguez-Gonzálvez, C., Shimwell, T. W., Davies, M. L., Feroz, F., Franzen, T. M. O., Grainge, K. J. B., Hobson, M. P., Hurley-Walker, N., Lasenby, A. N., Olamaie, M., Pooley, G., Saunders, R. D. E., Scaife, A. M. M., Schammel, M. P., Scott, P. F., Titterington, D. J. and Waldram, E. M. (2012), Detailed Sunyaev–Zel'dovich study with AMI of 19 LoCuSS galaxy clusters: masses and temperatures out to the virial radius. Monthly Notices of the Royal Astronomical Society, 425: 162–203. doi: 10.1111/j.1365-2966.2012.21419.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:34787
Deposited By: Ruth Sustaita
Deposited On:09 Oct 2012 21:11
Last Modified:09 Mar 2020 13:18

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