The Gravitational Lens CFRS 03.1077

An exquisite gravitational arc with a radius of 2.1" has been discoveredaround the z = 0.938 field elliptical galaxy CFRS03.1077 during HSTobservations of Canada-France Redshift Survey (CFRS) fields. Spectroscopicobservations of the arc show that the redshift of the resolved lensed galaxy isz = 2.941. This gravitational lens-source system is well-fitted using theposition angle and ellipticity derived from the visible matter distribution andan isothermal mass profile with a mass corresponding to sigma =387+-5 km/s.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 inthe significant evolution observed for average elliptical galaxies at z ~ 1. Asecond elliptical galaxy with similar luminosity from the CFRS survey, CFRS14.1311 at z=0.807, is also a lens but in this case the lens model gives a muchsmaller mass-to-light ratio, i.e., it appears to confirm the expectedevolution. This suggests that this pair of field elliptical galaxies may havevery different evolutionary histories, a significant result if confirmed.Clearly, CFRS03.1077 demonstrates that these "Einstein rings" are powerfulprobes of high redshift galaxies.Comment: 11 pages, 5 figures, accepted by Ap.