Gavazzi, Raphaël and Treu, Tommaso and Rhodes, Jason D. and Koopmans, Léon V. E. and Bolton, Adam S. and Burles, Scott and Massey, Richard J. and Moustakas, Leonidas A. (2007) The Sloan Lens ACS Survey. IV. The Mass Density Profile of Early-Type Galaxies out to 100 Effective Radii. Astrophysical Journal, 667 (1). pp. 176-190. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20100429-113331824
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We present a weak-lensing analysis of 22 early-type (strong) lens galaxies, based on deep HST images obtained as part of the Sloan Lens ACS Survey. Using advanced techniques to control systematic uncertainties, we show that weak-lensing signal is detected out to ~300 h^(-1) kpc (at the mean lens redshift z = 0.2). We analyze blank control fields from COSMOS in the same manner, inferring that the residual systematic uncertainty in the tangential shear is less than 0.3%. A joint strong- and weak-lensing analysis shows that the average total mass density profile is consistent with isothermal (i.e., ρ ∝ r^(-2)) over two decades in radius (3-300 h^(-1) kpc, approximately 1-100 effective radii). This finding extends by over an order of magnitude in radius previous results, based on strong lensing and/or stellar dynamics, that luminous and dark components "conspire" to form an isothermal mass distribution. In order to disentangle the contributions of luminous and dark matter, we fit a two-component mass model (de Vaucouleurs+NFW) to the weak- and strong-lensing constraints. It provides a good fit to the data with only two free parameters: (1) the average stellar mass-to-light ratio M_*/L_V = 4.48 ± 0.46 h M_☉ L_☉^(-1) (at z = 0.2), in agreement with that expected for an old stellar population; (2) the average virial mass-to-light ratio M_(vir)/L_V = 246^(+101)_(-87) h M_☉ L_☉^(-1). Taking into account the scatter in the mass-luminosity relation, the latter result is in good agreement with semianalytical models of massive galaxy formation. The dark matter fraction inside the sphere of radius, the effective radius, is found to be 27% ± 4%. Our results are consistent with galaxy-galaxy lensing studies of early-type galaxies that are not strong lenses, in the 30-300 h^(-1) kpc radius range. Thus, within the uncertainties, our results are representative of early-type galaxies in general.
|Additional Information:||© 2007 American Astronomical Society. Received 2007 January 18; accepted 2007 April 17. We thank Konrad Kuijken and Kevin Bundy for useful suggestions and Phil Marshall for a careful reading of the paper. We would also like to acknowledge insightful discussions with Alexie Leauthaud on the redshift distribution of sources in COSMOS. R. G., T. T., L. V. E. K., A. S. B., and L. A.M. would like to thank the Kavli Institute of Theoretical Physics and its staff for the warm hospitality during the program ‘‘Applications of Gravitational Lensing,’’ when a significant part of the work presented here was carried out. The work of L. A. M. was carried out at Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This research is supported by NASA through Hubble Space Telescope programs SNAP-10174, GO- 10494, SNAP-10587, GO-10798, and GO-10886 and in part by the National Science Foundation under grant PHY99-07949. T. T. acknowledges support from the NSF through CAREER award NSF-0642621. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This project would not have been feasible without the extensive and accurate database provided by the Sloan Digital Sky Survey (SDSS). Funding for the creation and distribution of the SDSS Archive has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Aeronautics and Space Administration, the National Science Foundation, the US Department of Energy, the Japanese Monbukagakusho, and the Max-Planck Society. The SDSSWeb site is http://www.sdss.org. The SDSS is managed by the Astrophysical Research Consortium (ARC) for the Participating Institutions. The Participating Institutions are the University of Chicago, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Korean Scientist Group, Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington.|
|Subject Keywords:||dark matter; galaxies: elliptical and lenticular, cD; galaxies: structure; gravitational lensing|
|Official Citation:||Raphaël Gavazzi et al 2007 ApJ 667 176 doi: 10.1086/519237|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||29 Apr 2010 20:43|
|Last Modified:||26 Dec 2012 11:59|
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