The emission lines are much broader than normal, having FWHM ~> 700 km
s^-1^. Inspection of the 2-D spectrum indicates that a very steep
rotation curve produces most of the observed line width. In this
respect, NGC 4866 is similar to NGC 5005, and more extreme than NGC 1052,
NGC 3884 and NGC 6500, all of which have line widths significantly
broadened by rotation (see Paper I for a more detailed discussion).
Hubble Atlas, p. 11
July 3/4, 1924
NGC 4866 is seen almost edge on. It is
classed as Sa because it is clearly not an S0; there
is dust throughout the disk in what appears to be
a spiral pattern, based on the appearance of the
outer disk on the right-hand side of the reproduction.
It is not as late as Sb, judged from the lack
of resolution of the disk into knots (HII regions)
or stellar associations.
In the Hubble Atlas (p. 11), NGC 4866 is
compared with NGC 2811 (panel 65 here), also
a very early Sa. Other galaxies of the same very
early Sa type are shown in the Sa section on
SA(r)0+: (de Vaucouleurs)
UGC 08091 at 11.8, 284
Very small, extremely bright nucleus partially hidden by dark lanes in lens.
(r): 2.4 arcmin x 0.3 arcmin.
Yerkes 2 classification: or DGK.
July 3/4, 1924
NGC 4866 is the prototype galaxy of the second major
subgroup of Sa systems. Very thin dust lanes are spread
throughout the main body. They are not circular but
have a tightly wound spiral pattern. NGC 4866 and NGC 2811
probably have a similar spiral pattern, but the projection
angles differ in the two galaxies. Notice the small nucleus
to NGC 4866. The entire lens is amorphous with no suggestion
of resolution into stars.