THE STRUCTURE AND DYNAMICS OF MASSIVE EARLY-TYPE GALAXIES: ON HOMOLOGY, ISOTHERMALITY, AND ISOTROPY INSIDE ONE EFFECTIVE RADIUSKoopmans, L. V. E., Bolton, A., Treu, T., Czoske, O., Auger, M. W., Barnabe, M., Vegetti, S., Gavazzi, R., Moustakas, L. A. & Burles, S., 20-Sep-2009, In : Astrophysical Journal Letters. 703, 1, p. L51-L54 4 p.
Research output: Contribution to journal › Article › Academic › peer-review
Based on 58 SLACS strong-lens early-type galaxies (ETGs) with direct total-mass and stellar-velocity dispersion measurements, we find that inside one effective radius maassive elliptical galaxies with M(eff) greater than or similar to 3 x 10(10) M(circle dot.) are well approximated by a power-law ellipsoid, with an average logarithmic density slope of equivalent to -d log(rho(tot))/d log(r) = 2.085(-0.018)(+0.025) and sigma(gamma') less than or similar to 0.20(-0.02)(+0.04) (random error on mean) for isotropic orbits with beta(r) = 0, +/- 0.1 (syst.) intrinsic scatter (all errors indicate the 68% CL). We find no correlation of gamma'(LD) with galaxy mass (M(eff)), rescaled radius (i.e., R(einst)/R(eff)) or redshift, despite intrinsic differences in density-slope between galaxies. Based on scaling relations, the average logarithmic density slope can be derived in an alternative manner, fully independent from dynamics, yielding = 1.959 +/- 0.077. Agreement between the two values is reached for = 0.45 +/- 0.25, consistent with mild radial anisotropy. This agreement supports the robustness of our results, despite the increase in mass-to-light ratio with total galaxy mass: M(eff) proportional to L(V,eff)(1.363 +/- 0.056). We conclude that massive ETGs are structurally close to homologous with close to isothermal total density profiles (less than or similar to 10% intrinsic scatter) and have at most some mild radial anisotropy. Our results provide new observational limits on galaxy formation and evolution scenarios, covering 4 Gyr look-back time.
|Number of pages||4|
|Journal||Astrophysical Journal Letters|
|Publication status||Published - 20-Sep-2009|
- galaxies: structure, gravitational lensing, LENS ACS SURVEY, ABSOLUTE MAGNITUDE RELATION, SUPERMASSIVE BLACK-HOLES, COLD DARK MATTER, ELLIPTIC GALAXIES, FUNDAMENTAL PLANE, SPHERICAL GALAXIES, GRAVITATIONAL LENSES, INTERNAL STRUCTURE, SAURON PROJECT