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Published December 1, 2009 | Published
Journal Article Open

The Distribution of Dark Matter Over Three Decades in Radius in the Lensing Cluster Abell 611

Abstract

We present a detailed analysis of the baryonic and dark matter distribution in the lensing cluster Abell 611 (z = 0.288), with the goal of determining the dark matter profile over an unprecedented range of cluster-centric distance. By combining three complementary probes of the mass distribution, weak lensing from multi-color Subaru imaging, strong lensing constraints based on the identification of multiply imaged sources in Hubble Space Telescope images, and resolved stellar velocity dispersion measures for the brightest cluster galaxy secured using the Keck telescope, we extend the methodology for separating the dark and baryonic mass components introduced by Sand et al. Our resulting dark matter profile samples the cluster from ~3 kpc to 3.25 Mpc, thereby providing an excellent basis for comparisons with recent numerical models. We demonstrate that only by combining our three observational techniques can degeneracies in constraining the form of the dark matter profile be broken on scales crucial for detailed comparisons with numerical simulations. Our analysis reveals that a simple Navarro-Frenk-White (NFW) profile is an unacceptable fit to our data. We confirm earlier claims based on less extensive analyses of other clusters that the inner profile of the dark matter profile deviates significantly from the NFW form and find a inner logarithmic slope β flatter than 0.3 (68%; where ρ_(DM) ∝ r^(–β) at small radii). In order to reconcile our data with cluster formation in a ΛCDM cosmology, we speculate that it may be necessary to revise our understanding of the nature of baryon-dark matter interactions in cluster cores. Comprehensive weak and strong lensing data, when coupled with kinematic information on the brightest cluster galaxy, can readily be applied to a larger sample of clusters to test the universality of these results.

Additional Information

© 2009 American Astronomical Society. Print publication: Issue 2 (2009 December 1); received 2009 May 12; accepted for publication 2009 September 21; published 2009 November 10. We are grateful to Steve Allen for kindly providing X-ray measurements of the Abell 611 gas profile, and to Herv´e Aussel, Hisanori Furusawa, and Yutaka Komiyama for assistance with photometric calibration. We thank Eric Jullo, Jason Rhodes, Joel Berge, Jean-Paul Kneib, Graham Smith, Richard Massey, and Simon White for their assistance and stimulating discussion. We acknowledge the anonymous referee for helpful suggestions. R.S.E. acknowledges financial support from the Royal Society. J.R. acknowledges support from an EU Marie Curie fellowship. T.T. acknowledges support from the NSF through CAREER award NSF-0642621, by the Sloan Foundation through a Sloan Research Fellowship, and by the Packard Foundation through a Packard Fellowship. The authors wish to recognize and acknowledge the cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This research has made use of the NASA/IPAC Extragalactic Database, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

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August 21, 2023
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October 19, 2023