The redshift of the galaxy lensing HE 0435 - 1223 is 0.4546 \pm 0.0002 , based on observations obtained with the Low Dispersion Survey Spectrograph 2 ( LDSS2 ) on the Magellan Consortium ’ s 6.5 m Clay telescope . Hubble Space Telescope /ACS observations of the system also reveal a spiral-rich group of 10 galaxies within 40″ of the elliptical lensing galaxy .
The redshifts for two of these galaxies were measured to be in the foreground ( at z = 0.419 ) with respect to the lens , thus at least some of the nearby galaxies are not part of the same physical group as the lensing galaxy .
Mass models of the system ( assuming same-plane deflectors ) that take the local group environment into account do better at explaining the observed emission-line flux ratios ( which are presumably unaffected by microlensing ) than single halo models , but the match is still not perfect .
In particular , component A ( a minimum of the light travel time ) is observed to be 0.20 mag brighter than predicted and component C ( also a minimum image ) is observed to be 0.16 mag fainter than predicted .
Mass models for the system predict an A–D time delay of either 15.8 or 17.6 days ( H _ { o } = 72 km s ^ { -1 } Mpc ^ { -1 } ) depending on the details of the local galaxy environment .