Detailed Sunyaev-Zel'dovich study with AMI of 19 LoCuSS galaxy clusters: Masses and temperatures out to the virial radius

Carmen Rodríguez-Gonzálvez, Timothy W. Shimwell, Matthew L. Davies, Farhan Feroz, Thomas M O Franzen, Keith J B Grainge, Michael P. Hobson, Natasha Hurley-Walker, Anthony N. Lasenby, Malak Olamaie, Guy Pooley, Richard D E Saunders, Anna M M Scaife, Michel P. Schammel, Paul F. Scott, David J. Titterington, Elizabeth M. Waldram

    Research output: Contribution to journalArticlepeer-review


    We present detailed 16-GHz interferometric observations using the Arcminute Microkelvin Imager (AMI) of 19 clusters with L X > 7 × 10 37W (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 ± 0.1Mpc 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 MT, AMI /MT, WL =1.2-0.3+0.2 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. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.
    Original languageEnglish
    Pages (from-to)162-203
    Number of pages41
    JournalMonthly Notices of the Royal Astronomical Society
    Issue number1
    Publication statusPublished - 1 Sep 2012


    • Cosmic background radiation
    • Galaxies: clusters: general
    • Galaxies: clusters: intracluster medium
    • Large-scale structure of Universe
    • Methods: observational
    • Techniques: interferometric


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