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Published September 21, 2012 | Published
Journal Article Open

X-ray, lensing and Sunyaev–Zel'dovich triaxial analysis of Abell 1835 out to R₂₀₀


The measurement of the intrinsic shape and orientation of dark matter (DM) and intracluster (IC) gas in galaxy clusters is crucial for constraining their formation and evolution, and for enhancing the use of clusters as more precise cosmological probes. Extending our previous works, for the first time we present the results from a triaxial joint analysis of the galaxy cluster Abell 1835, using X-ray, strong lensing (SL) and Sunyaev–Zel'dovich (SZ) data. We parametrically reconstruct the full three-dimensional structure (triaxial shape and principal axis orientation) of both the DM and the IC gas, and the level of non-thermal pressure of the IC gas. We find that the intermediate–major and minor–major axial ratios of the DM are 0.71 ± 0.08 and 0.59 ± 0.05, respectively, and that the major axis of the DM halo is inclined with respect to the line of sight at 18.3 ± 5.2 deg. We present the first observational measurement of the non-thermal pressure out to R200. This has been evaluated to be a few per cent of the total energy budget in the internal regions, while it reaches approximately 20 per cent in the outer volumes. We discuss the implications of our method for the viability of the cold dark matter (CDM) scenario, focusing on the concentration parameter C and the inner slope of the DM γ in order to test the CDM paradigm for structure formation. We measure γ = 1.01 ± 0.06 and C = 4.32 ± 0.44; these values are close to the predictions of the CDM model. The combination of X-ray/SL data at high spatial resolution, which are capable of resolving the cluster core, with the SZ data, which are more sensitive to the cluster outer volume, allows us to characterize the level and the gradient of the gas entropy distribution and non-thermal pressure out to R200. Thus, we break the degeneracy among the physical models describing the thermal history of the intracluster medium.

Additional Information

© 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS. Accepted 2012 April 26. Received 2012 April 21; in original form 2011 November 24. AM acknowledges support from the Israel Science Foundation grant 823/09. ML acknowledges the Centre National de la Recherche Scientifique (CNRS) for its support. The Dark Cosmology Centre is funded by the Danish National Research Foundation. This work has been conducted using facilities offered by the Centre de Données Astrophysique de Marseille (CeSAM; http://lam.oamp.fr/cesam/). JS was partially supported by a NASA Graduate Student Research Fellowship and a NASA Postdoctoral Programme fellowship (NSF/AST-0838261 and NASA/NNX11AB07G). NC was partially supported by a NASA Graduate Student Research Fellowship. Bolocam observations and analyses were also supported by the Gordon and Betty Moore Foundation. Bolocam was constructed and commissioned using funds from NSF/AST-9618798, NSF/AST-0098737, NSF/AST-9980846, NSF/AST-0229008 and NSF/AST-0206158. SA and EP were partially supported by the National Science Foundation grant AST-0649899. SA was partially supported by a postdoctoral fellowship and travel grants from the University of Southern California (USC) Women in Science and Engineering (WiSE) programme, and EP was partially supported by a NASA grant NNXO7AH59G and JPL-Planck subcontract 1290790. The spectroscopic optical data are based on observations collected at the European Southern Observatory, Chile.

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