6. Implications for the lensing galaxy
As is still unknown, we cannot use this formula to get . However, simply adopting a canonical value for allows us to predict the redshift of the lens, or better, to constrain the range of possible values for . Fig. 4 shows the product of time delay and Hubble parameter as a function of . For , , , and , the SIST model predicts , and the velocity dispersion of the galaxy for this model is . This corresponds to a mass of inside of one Einstein radius, well within the range expected for a reasonably massive galaxy. With an band magnitude of 20.9 according to R98, the mass-to-light ratio would then be of the order of 10 solar units, again quite consistent with the expectations for such a galaxy (cf. Keeton et al. 1998).
Recently, values for the time delay have been predicted based on the assumption that one of the two strong metal absorption line systems at or can be identified with the deflector. R98 give yrs, Courbin et al. (1998) even yrs. Since we can reliably exclude yr, our results are not compatible with significantly larger than 1; in particular, the absorbers at 1.32 and 1.66 can be ruled out.
We have searched our higher resolution NTT spectra of HE 1104-1805 (cf. Lopez et al. 1998) for absorption lines within the redshift range permitted by Fig. 4. An additional demand is that the lines should be stronger in A, as this component is located closer to the deflector. Two Mg II absorption systems, at and 0.73, meet the criteria. Of these, is acceptable only for a time delay as short as yrs, and is furthermore not compatible with the colour estimate of R98. This leaves the system at as candidate; however, the lens could also be an elliptical galaxy for which Mg II absorption would be a poor indicator. The very red colours measured by R98 support such a notion.
© European Southern Observatory (ESO) 1998
Online publication: October 22, 1998