NGC 3681.---SB(r)0/a: Nuclear point source, threaded by short nuclear
bar. The bar causes the bulge isophotes to be very elliptical. Bulge
is embedded in a smooth inner disk, with a complete inner ring at its
edge. The disk surface brightness drops abruptly outside of the ring.
The outer disk is LSB, and smooth, with no evidence of any spiral
structure. The optical types for this galaxy are SAB(r)bc (RC3),
SBb(r)I--II (CAG), and SAB(r)b (OSU B). The substantially earlier type
in the near-IR is due to the lack of obvious spiral structure in the H
NGC 3681. - We did not detect a radio source on the untapered or
tapered maps. In contrast, NVSS measured a weak source of about 4.2 mJy
at much lower resolution.
UGC 6445 a galaxy with a small oval component, has a less pronounced Type II
profile. Because of a slight shift in steepness of the luminosity profile in
the outer region of the galaxy, the r^1/4^ fit will tend to dominate in the
central and outer region. Consequently bulge and disk are equally important
over the whole extent of the galaxy in such a fit. Inclusion of a bar or oval
component immediately diminishes the bulge contribution at large radii, even if
one would fit an r^1/4^ bulge profile. Clearly the 2D fit is the best option
for this galaxy.
April 2/3, 1981
The bar in NGC 3681 is a central oval, not
a well-defined feature as in NGC 1300. The
classification in the RC2 is that of a transition
type between barred and ordinary spiral,
The arm type is multiple (MAS) and fragmented.
A set of high-surface-brightness inner
arms exists, together with a set of
low-surface-brightness outer arms.
HII regions occur in both arm sets. They are
unresolved at the 1" level. The redshift of
NGC 3681 is v_o = 1135 km/s.
Non-interacting pair with NGC 3684 at 14 arcmin
SAB(r)bc (de Vaucouleurs)
Bright inner region 1.2 x 1.2
UGC 06453 at 14., 44
Bright diffuse nucleus in a smooth, bright, inner lens or bar: 0.35 arcmin
x 0.25 arcmin. (r): 0.6 arcmin x 0.55 arcmin. Many filamentary, knotty,
Non-interacting pair with NGC 3684 at 14 arcmin.
Lund 9 dimensions are for the bright part only.
A spiral 1' in diameter. Whorls form a nearly perfect ring.