Gravitational lensing of the farthest known supernova SN1997ff

Résumé : We investigate the effects of gravitational lensing due to intervening galaxies on the recently discovered Type Ia supernova at z=1.7, SN1997ff, in the Hubble Deep Field North. We find that it is possible to obtain a wide range of magnifications by varying the mass and/or the velocity dispersion normalization of the lensing galaxies. In order to be able to use SN1997ff to constrain the redshift-distance relation, very detailed modeling of the galaxies to control the systematic effects from lensing is necessary. Thus we argue, that based on our current limited knowledge of the lensing galaxies, it is difficult to use SN1997ff to constrain the values of Omega_M and Omega_Lambda, or even to place severe limits on grey dust obscuration or luminosity evolution of Type Ia supernovae.