NGC 1738/9 comprises an SBbc-Sbc pair for which our single
spectroscopic slit position did not pass through background areas
symmetric to our regions of interest (see Fig. 7), due to geometric
constraints. We were, however, able to estimate opacities despite the
velocity separation being less than 100 km s^-1^. Cross-correlation of
spectra from the overlap region proved to be easiest with the nuclear
spectrum of NGC 1738. In combination with the B-image/spectrum method,
three 1 pixel (0.2 kpc) wide regions reveal an average apparent
A_B_ = 0.76 for these arm regions. Dividing by the axial ratio of the
foreground galaxy NGC 1739 (a/b = 1.95) yields a face-on-corrected value
of A_B_ = 0.39, which is in general agreement with our previous
photometric analysis of this pair (White et al. 2000).
Figures 4a and 4b are B and B-I images, respectively, of the Sbc pair
NGC 1738/9. The symmetry of this system is not good enough to do an
opacity analysis in the same detail as for AM 1316-241 and AM 0500-620.
Instead, the two regions indicated in Figure 4a are investigated: a
foreground arm region at 0.65 R_25_^B^ and an interarm region at 0.55
R_25_^B^. Symmetric regions in the foreground and background galaxies
are used to infer the apparent extinction in B and I in these two
regions. The apparent extinction values of the foreground galaxy
(NGC 1739) are divided by its axial ratio of 1.95 (indicating an
inclination of 59^deg^) to give the face-on-corrected values listed in
Table 3. The face-on extinctions are again quite low: in the arm region,
A_B_ = 0.3-0.37 and A_I_ = 0.24 -0.28, while in the interarm region,
A_B_ = 0.2-0.26 and A_I_ = 0.17.
Overexposed center, pretty faint arms with few knots. Interacting pair
with NGC 1738 at 0.55. Superposed on small cluster.
=ESO 552- G 50
partly in front of ESO 552- G 49
Interacting pair (with MCG -03-13-054) of very perturbed galaxies.