The Gravitational Lens CFRS 03.1077

Abstract

An exquisite gravitational arc with a radius of 2.1" has been discovered around the z=0.938 field elliptical galaxy CFRS 03.1077 during HST observations of Canada-France Redshift Survey (CFRS) fields. Spectroscopic observations of the arc show that the redshift of the resolved lensed galaxy is z=2.941. This gravitational lens source system is well fitted using the position angle and ellipticity derived from the visible matter distribution and an isothermal mass profile with a mass corresponding to σ=387+/-5 km s^-1. Surprisingly, given the evidence for passive evolution of elliptical galaxies, this is in good agreement with an estimate based on the fundamental plane for z=0 ellipticals. This, perhaps, indicates that this galaxy has not shared in the significant evolution observed for average elliptical galaxies at z~1. A second elliptical galaxy with similar luminosity from the CFRS survey, CFRS 14.1311 at z=0.807, is also a lens, but in this case the lens model gives a much smaller mass-to-light ratio; i.e., it appears to confirm the expected evolution. This suggests that this pair of field elliptical galaxies may have very different evolutionary histories, which would be a significant result if confirmed. Clearly, CFRS 03.1077 demonstrates that these ``Einstein rings'' are powerful probes of high-redshift galaxies. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy Inc., under NASA contract NAS 5-26555.