The XMM Cluster Survey: testing chameleon gravity using the profiles of clusters

Harry Wilcox, David Bacon, Robert C. Nichol, Philip J. Rooney, Ayumu Terukina, A. Kathy Romer, Kazuya Koyama, Gong-Bo Zhao, Ross Hood, Robert G. Mann, Matt Hilton, Maria Manolopoulou, Martin Sahlen, Chris A. Collins, Andrew R. Liddle, Julian A. Mayers, Nicola Mehrtens, Christopher J. Miller, John P. Stott, Pedro T. P. Viana

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The chameleon gravity model postulates the existence of a scalar field that couples with matter to mediate a fifth force. If it exists, this fifth force would influence the hot X-ray emitting gas filling the potential wells of galaxy clusters. However, it would not influence the clusters' weak lensing signal. Therefore, by comparing X-ray and weak lensing profiles, one can place upper limits on the strength of a fifth force. This technique has been attempted before using a single, nearby cluster (Coma, z=0.02). Here we apply the technique to the stacked profiles of 58 clusters at higher redshifts (0.1 < z < 1.2 ), including 12 new to the literature, using X-ray data from the XMM Cluster Survey (XCS) and weak lensing data from the Canada France Hawaii Telescope Lensing Survey (CFHTLenS). Using a multiparameter MCMC analysis, we constrain the two chameleon gravity parameters (β and φ). Our fits are consistent with general relativity, not requiring a fifth force. In the special case of f(R) gravity (where β =√1/6), we set an upper limit on the background field amplitude today of |fR0|< 6 × 10−5 (95% CL). This is one of the strongest constraints to date on |fR0| on cosmological scales. We hope to improve this constraint in future by extending the study to hundreds of clusters using data from the Dark Energy Survey.
Original languageEnglish
Pages (from-to)1171-1183
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date14 Jul 2015
Publication statusPublished - 11 Sept 2015


  • astro-ph.CO
  • RCUK
  • STFC
  • DB, RN, AKR, KK and ARL are supported by the UK STFC grants ST/K00090/1, ST/K00090/1, STL000652/1, ST/L005573/1 and ST/L000644/1
  • gravitation
  • gravitational lensing: weak
  • X-rays: galaxies: clusters


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