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The Sloan Lens ACS Survey: X. Stellar, Dynamical, and Total Mass Correlations of Massive Early-type Galaxies

Auger, M. W., Treu, T., Bolton, A. S., Gavazzi, R., Koopmans, L. V. E., Marshall, P. J., Moustakas, L. A. & Burles, S., Nov-2010, In : Astrophysical Journal. 724, 1, p. 511-525 15 p.

Research output: Contribution to journalArticleAcademicpeer-review

  • M. W. Auger
  • T. Treu
  • A. S. Bolton
  • R. Gavazzi
  • L. V. E. Koopmans
  • P. J. Marshall
  • L. A. Moustakas
  • S. Burles

We use stellar masses, surface photometry, strong-lensing masses, and stellar velocity dispersions (sigma(e/2)) to investigate empirical correlations for the definitive sample of 73 early-type galaxies (ETGs) that are strong gravitational lenses from the SLACS survey. The traditional correlations (fundamental plane (FP) and its projections) are consistent with those found for non-lens galaxies, supporting the thesis that SLACS lens galaxies are representative of massive ETGs (dimensional mass M(dim) = 10(11)-10(12) M(circle dot)). The addition of high-precision strong-lensing estimates of the total mass allows us to gain further insights into their internal structure: (1) the average slope of the total mass-density profile (rho(tot) alpha r(-gamma)') is = 2.078 +/- 0.027 with an intrinsic scatter of 0.16 +/- 0.02; (2) gamma' correlates with effective radius (r(e)) and central mass density, in the sense that denser galaxies have steeper profiles; (3) the dark matter (DM) fraction within r(e)/2 is a monotonically increasing function of galaxy mass and size (due to a mass-dependent central cold DM distribution or due to baryonic DM-stellar remnants or low-mass stars-if the initial mass function is non-universal and its normalization increases with mass); (4) the dimensional mass M(dim) equivalent to 5r(e)sigma(2)(e/2)/G is proportional to the total (lensing) mass M(re/2), and both increase more rapidly than stellar mass M(*) (M(*) alpha M(re/2)(0.8)); (5) the mass plane (MP), obtained by replacing surface brightness with surface mass density in the FP, is found to be tighter and closer to the virial relation than the FP and the M(*)P, indicating that the scatter of those relations is dominated by stellar population effects; (6) we construct the fundamental hyper-plane by adding stellar masses to the MP and find the M(*) coefficient to be consistent with zero and no residual intrinsic scatter. Our results demonstrate that the dynamical structure of ETGs is not scale invariant and that it is fully specified by M(re/2), r(e), and sigma(e/2). Although the basic trends can be explained qualitatively in terms of varying star formation efficiency as a function of halo mass and as the result of dry and wet mergers, reproducing quantitatively the observed correlations and their tightness may be a significant challenge for galaxy formation models.

Original languageEnglish
Pages (from-to)511-525
Number of pages15
JournalAstrophysical Journal
Volume724
Issue number1
Publication statusPublished - Nov-2010

    Keywords

  • dark matter, galaxies: elliptical and lenticular, cD, galaxies: fundamental parameters, galaxies: structure, gravitational lensing: strong, DIGITAL SKY SURVEY, DARK-MATTER HALOS, TO-LIGHT RATIOS, FUNDAMENTAL PLANE, ELLIPTIC GALAXIES, SCALING RELATIONS, INTERNAL STRUCTURE, HUBBLE CONSTANT, VELOCITY DISPERSIONS, GRAVITATIONAL LENSES

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