The Density Profiles of Massive, Relaxed Galaxy Clusters. I. The Total Density Over Three Decades in Radius
Abstract
Clusters of galaxies are excellent locations to probe the distribution of baryons and dark matter (DM) over a wide range of scales. We study a sample of seven massive (M_(200) = 0.4-2 × 10^(15) M_☉), relaxed galaxy clusters with centrally located brightest cluster galaxies (BCGs) at z = 0.2-0.3. Using the observational tools of strong and weak gravitational lensing, combined with resolved stellar kinematics within the BCG, we measure the total radial density profile, comprising both dark and baryonic matter, over scales of ≃3-3000 kpc. We present Keck spectroscopy yielding seven new spectroscopic redshifts of multiply imaged sources and extended stellar velocity dispersion profiles of the BCGs. Lensing-derived mass profiles typically agree with independent X-ray estimates within ≃15%, suggesting that departures from hydrostatic equilibrium are small and that the clusters in our sample (except A383) are not strongly elongated or compressed along the line of sight. The inner logarithmic slope γ_(tot) of the total density profile measured over r/r_(200) = 0.003-0.03, where P_(tot) ∝ r-Y^(tot), is found to be nearly universal, with a mean γ_(tot) = 1.16 ± 0.05(random)^(+0.05)_(–0.07) (systematic) and an intrinsic scatter σ_γ < 0.13 (68% confidence). This is further supported by the very homogeneous shape of the observed velocity dispersion profiles, which are mutually consistent after a simple scaling. Remarkably, this slope agrees closely with high-resolution numerical simulations that contain only DM, despite the significant contribution of stellar mass on the scales we probe. The Navarro-Frenk-White profile characteristic of collisionless cold DM is a better description of the total mass density at radii ≳5-10 kpc than that of DM alone. Hydrodynamical simulations that include baryons, cooling, and feedback currently provide a poorer match. We discuss the significance of our findings for understanding the physical processes governing the assembly of BCGs and cluster cores, particularly the influence of baryons on the inner DM halo.
Additional Information
© 2013 American Astronomical Society. Received 2012 September 21; accepted 2012 December 21; published 2013 February 13. It is a pleasure to acknowledge insightful conversations with Annika Peter. We thank Liang Gao, Davide Martizzi, and Jesper Sommer-Larsen for providing tabulated results from their simulations. The anonymous referee is thanked for a helpful report. R.S.E. acknowledges financial support from DOE grant DE-SC0001101. Research support by the Packard Foundation is gratefully acknowledged by T.T. J.R. is supported by the Marie Curie Career Integration grant 294074. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the NASA. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors 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. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. This research has made use of data obtained from the Chandra Data Archive and software provided by the Chandra X-ray Center (CXC). Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.Attached Files
Published - 0004-637X_765_1_24.pdf
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Additional details
- Eprint ID
- 37713
- Resolver ID
- CaltechAUTHORS:20130402-091629499
- DE-SC0001101
- Department of Energy (DOE)
- David and Lucile Packard Foundation
- 294074
- Marie Curie Fellowship
- W. M. Keck Foundation
- NAS 5-26555
- NASA
- Created
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2013-04-02Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field