NGC 3314, a remarkable superposition of two spirals in the Hydra
Cluster (Abell 1060), was considered in the context of opacity
measurements by Keel (1983). Our more recent imaging allows us to
greatly improve upon these measurements (B and B-I images are shown in
Figs. 9a and 9b). Following McMahon et al. (1992), we will call the
foreground Sc galaxy NGC 3314a and the background Sab system NGC 3314b.
Color-index maps, the symmetry of rotation curves (Schweizer & Thonnard
1985), and our K-band imagery show that the nuclei are separated by only
1.8". We cannot do as complete an analysis here as for the best-case
partial overlaps with a background E/S0 galaxy because (1) the
background object is a spiral (albeit of early type) and (2) the overlap
is so nearly central that there is no empirical check on the brightness
profile of the background galaxy. However, this system is uniquely
valuable because we can estimate extinctions in the foreground galaxy
closer to its center than in any other sample member.
The best places for reliable extinction measurements are the points
where the arms of NGC 3314a cross the disk edges of NGC 3314b, going
from projection against the bright disk to projection against almost
blank space at essentially the same radial distance for the arm. We
measured the arm intensities at adjacent points on and off the
background disk, after subtracting a minimal exponential-disk model to
flatten most of the background gradient (so that interpolation to get
the relevant unobscured background intensity is better constrained). For
several locations where the arms cross the disk between 0.16 and
0.42R_25_, A_B_ ranges from 0.9 to 1.3 mag, while A_I_ ranges from 0.7 to
1 mag (face-on corrected, with a/b = 1.22). For interarm regions between
0.19 and 0.39R_25_, the (face-on-corrected) extinctions remain high:
A_B_~ 0.6-1.4 and A_I_ ~ 0.5-1.3. The spiral pattern in NGC 3314a is
defined more by the dust lanes than by the stellar distribution.
The H I maps presented by McMahon et al. (1992) afford a chance for a
crude measurement of the dust-to-gas ratio, as represented by
N(H I)/E(B-V), limited by the resolution of their VLA H I synthesis
(FWHM about 14"), as compared to the arm width (traced by optical
extinction) of about 5" in the regions we have analyzed. Their Figures 3
and 4 suggest an H I column density of about 10^21^ cm^-2^, and
application of the usual Galactic extinction law to our values of A_B_
implies a ratio N(H I)/E(B-V) > 2.8 x 10^21^ cm^-2^; the upper limit is
due to the likelihood that the H I is clumped into arms not well
resolved in the H I map. Thus, we find a ratio of the same order as in
our local neighborhood, and it is not clear how close a correspondence
we should expect even for identical grain populations as a result of the
effects of unresolved clumping on the spatially averaged extinction
values we measure.
Appears cigar-shaped with plumes around. Similar to NGC 2685. Face-on SAc:
superposed on edge-on Sb:. Extension to 3.5 south-preceding nucleus?
Sc superposed on S0/a, interacting(?) pair. Possibly = NGC 3315?
=ESO 501-IG 46
contact or superimposed?
In the Hydra Cluster (Abell 1060).
Extremely small, very bright nucleus. Bar: 1.2 arcmin x 0.25 arcmin, with
dark lanes. Faint outer asymmetric arm. Perhaps this is a colliding or
strongly interacting pair?
In the Hydra I Cluster.