Abstract
A small proportion of elliptical and lenticular galaxies show
evidence of well-defined dust-lanes when examined on deep survey plates.
New near-infrared (JHK) observations of 46 dust-lane galaxies are presented
and compared with those for a sample of 24 morphologigally normal systems.
Infrared excesses are found preferentially in galaxies which exhibit at
least weak signs of a stellar disc ; the physics of the emission mechanism
is discussed in the light of additional 3.5 y observations and published
optical spectra. The most extreme properties are those of the heavily
obscured edge-on galaxy NGC7172. In this case, the infrared emission is
variable on a timescale ^0.5 yrs. New optical spectra are also discussed
and support the identification of the hard X-ray source H2158-321 with
this galaxy.
A restricted sample of 'elliptical-like' galaxies with dust-lanes,
but containing no significant luminous disc, has been defined. It is
demonstrated that these galaxies cannot be distinguished from a comparable
sample of morphologically normal ellipticals on the basis of UBV colours
or luminosity. Four examples have been selected for a detailed study of
their structure and dynamics. Rotation curves and velocity dispersion
profiles have been derived from long-slit spectra using Fourier analysis
techniques ; surface photometry was obtained from large-scale photographic
plates. The data reduction and analysis techniques are discussed in some
detail. In three cases the angular momentum axis of the dust-lane is
different from that of the stellar component, favouring an external origin
for the dust and gas. Two of the galaxies rotate as rapidly as oblate
models with isotropic velocity dispersions ; this property is characteristic.
of the luminous bulges in disc systems. The orientation of the dust-lane
favours a prolate geometry for one of these bulges. It is demonstrated
that the kinematics are inconsistent with two recently published models
of prolate.galaxies.