Constraints on H0 from the Central Velocity Dispersions of Lens Galaxies
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 h4 observed in nearby galaxies for 0 < R < 2 Reff. For Q0957+561, we find a 16% uncertainty in the galaxy mass, and formal 2-sigma limits on the Hubble constant of H0 = (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 H0 is not yet strongly constrained by this system.
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