H_0 from gravitational lenses: recent results
Abstract
Description
The 0th, 1st and 2nd derivatives of a ``Fermat potential'' give the three D's of gravitational lensing: delay, deflection and distortion. Observations of these delays, deflections and distortions for doubly and quadruply imaged quasars give estimates of Hubble's constant, H_0. The single largest contribution to the uncertainty in H_0 arises from the difficulty in constraining the degree of central concentration of the lensing potential. Fortunately, astronomers have spent a good deal of effort over the past quarter century addressing just this question. If galaxies at z=0.5 are like nearby galaxies, the associated systematic uncertainty in H_0 is less than 10%. The expected lens-to-lens scatter is 20%. Results from three particularly well constrained systems are reported.
10 pages, no figures, uses newpasp.sty, invited review to be published in IAU Symposium No. 201: New Cosmological and the Values of the Fundamental Parameters, eds. A.N. Lasenby and A. Wilkinson
10 pages, no figures, uses newpasp.sty, invited review to be published in IAU Symposium No. 201: New Cosmological and the Values of the Fundamental Parameters, eds. A.N. Lasenby and A. Wilkinson