Publication

The Sloan Lens ACS survey. IV. The mass density profile of early-type galaxies out to 100 effective radii

Gavazzi, R., Treu, T., Rhodes, J. D., Koopmans, L. V. E., Bolton, A. S., Burles, S., Massey, R. J. & Moustakas, L. A., 20-Sep-2007, In : Astrophysical Journal. 667, 1, p. 176-190 15 p.

Research output: Contribution to journalReview articleAcademicpeer-review

  • Raphael Gavazzi
  • Tommaso Treu
  • Jason D. Rhodes
  • Leon V. E. Koopmans
  • Adam S. Bolton
  • Scott Burles
  • Richard J. Massey
  • Leonidas A. Moustakas

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 similar 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., rho proportional to 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 (deVaucouleurs+NFW) to the weak- and strong-lensing constraints. It provides a good fit to the datawith only two free parameters: (1) the average stellar mass-to-light ratio M-*/L-V =4.48 +/- 0.46 h M-circle dot L-circle dot(-1) (at z = 0.2), in agreement with that expected for an old stellar population; (2) the average virialmass-to-light ratio M-vir/L-V = 246(-87)(+101) h M-circle dot L-circle dot(-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.

Original languageEnglish
Pages (from-to)176-190
Number of pages15
JournalAstrophysical Journal
Volume667
Issue number1
Publication statusPublished - 20-Sep-2007

    Keywords

  • dark matter, galaxies : elliptical and lenticular, cD, galaxies : structure, gravitational lensing, DARK-MATTER HALOS, DIGITAL SKY SURVEY, HUBBLE-SPACE-TELESCOPE, TO-LIGHT RATIOS, LINE-OF-SIGHT, ELLIPTIC GALAXIES, FUNDAMENTAL PLANE, STELLAR MASS, INTERMEDIATE-REDSHIFT, DOMINATED GALAXIES

ID: 4612847