(Abridged) A new technique for the spatial deconvolution of spectra is
applied to near-IR (0.95 - 2.50 micron) NTT/SOFI spectra of the lensed,
radio-quiet quasar HE 1104-1805. The continuum of the lensing galaxy is
revealed between 1.5 and 2.5 micron. It is used in combination with previous
optical and IR photometry to infer a plausible redshift in the range 0.8 < z <
1.2. Modeling of the system shows that the lens is probably composed of the red
galaxy seen between the quasar images and a more extended component associated
with a galaxy cluster with fairly low velocity dispersion (~ 575 km/s). The
spectra of the two lensed images of the source show no trace of reddening at
the redshift of the lens nor at the redshift of the source. Additionally, the
difference between the spectrum of the brightest component a nd that of a
scaled version of the faintest component is a featureless continuum. Broad and
narrow emission lines, including the FeII features, are perfectly subtracted.
The very good quality of our spectrum makes it possible to fit precisely the
optical Fe II feature, taking into account the underlying continuum over a wide
wavelength range. HE 1104-1805 can be classified as a weak Fe II emitter.
Finally, the slope of the continuum in the brightest image is steeper than the
continuum in the faintest image and supports the finding by Wisotzki et al.
(1993) that the brightest image is microlensed. This is particularly
interesting in view of the new source reconstruction methods from
multiwavelength photometric monitoring.Comment: to be published in A&A, 8 pages, 9 postscript figure
