paper

Constraints on H_0 from the Central Velocity Dispersions of Lens Galaxies

arXiv:astro-ph/9805080 · doi:10.1086/307077

Abstract

We employ Schwarzschild's method of orbit modeling to constrain the mass profiles of the central lens galaxies in Q0957+561 and PG 1115+080. We combine the measured central projected stellar velocity dispersions of these galaxies with the self-similar radial profiles of the rms velocity and of the Gauss-Hermite moment h_4 observed in nearby galaxies for 0 < R < 2 R_eff. For Q0957+561, we find a 16% uncertainty in the galaxy mass, and formal 2-sigma limits on the Hubble constant of H_0 = (61 +13/-15) km/s/Mpc. For PG 1115+080, we find that none of the viable lens models can be ruled out, so that H_0 is not yet strongly constrained by this system.

Revised version accepted by ApJ: slightly modified results for both lens sytems. 18 pages, with 7 inline Postscript figures, LaTeX, aaspp4.sty; postscript paper w/figs (490 kb) also available at http://cfa-www.harvard.edu/~romanow/orbit.post.v2.ps.gz

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