The Sloan Lens ACS Survey. VII. Elliptical galaxy scaling laws from direct observational mass measurementsBolton, A. S., Treu, T., Koopmans, L. V. E., Gavazzi, R., Moustakas, L. A., Burles, S., Schlegel, D. J. & Wayth, R., 1-Sep-2008, In : Astrophysical Journal. 684, 1, p. 248-259 12 p.
Research output: Contribution to journal › Review article › Academic › peer-review
We use a sample of 53 massive early-type strong gravitational lens galaxies with well-measured redshifts (ranging from z = 0.06 to 0.36) and stellar velocity dispersions (between 175 and 400 km s(-1)) from the Sloan Lens ACS (SLACS) Survey to derive numerous empirical scaling relations. The ratio between central stellar velocity dispersion and isothermal lens-model velocity dispersion is nearly unity within errors. The SLACS lenses define a fundamental plane (FP) that is consistent with the FP of the general population of early-type galaxies. We measure the relationship between strong-lensing mass M-lens within one-half effective radius (R-e/2) and the dimensional mass variable M-dim equivalent to G(-1) sigma(2)(e2)(R-e/2) to be log (M-lens/10(11) M-circle dot) = (1.03 +/- 0.04) log (M-dim/10(11) M-circle dot)+ (0.54 +/- 0.02) (where sigma(e2) is the projected stellar velocity dispersion within R-e/2). The near-unity slope indicates that the mass-dynamical structure of massive elliptical galaxies is independent of mass and that the "tilt'' of the SLACS FP is due entirely to variation in total (luminous plus dark) mass- to-light ratio with mass. Our results imply that dynamical masses serve as a good proxies for true masses in massive elliptical galaxies. Regarding the SLACS lenses as a homologous population, we find that the average enclosed two-dimensional (2D) mass profile goes as log[M(<R)/M-dim]=(1.10 +/- 0.09)log(R/ R-e)+(0.85 +/- 0.03), consistent with an isothermal (flat rotation curve) model when deprojected into three dimensions (3D). This measurement is inconsistent with the slope of the average projected aperture luminosity profile at a confidence level greater than 99.9%, implying a minimum dark matter fraction of f(DM) = 0.38 +/- 0.07 within 1 effective radius. We also present an analysis of the angular mass structure of the lens galaxies, which further supports the need for dark matter inside one effective radius.
|Number of pages||12|
|Publication status||Published - 1-Sep-2008|
- galaxies : elliptical and lenticular, cD, gravitational lensing, surveys, DIGITAL SKY SURVEY, TO-LIGHT RATIO, SIGHT VELOCITY DISTRIBUTIONS, INFRARED FUNDAMENTAL PLANE, ABSORPTION-LINE SPECTRA, 3RD DATA RELEASE, GRAVITATIONAL LENS, DARK-MATTER, EINSTEIN RING, KECK SPECTROSCOPY