A multiwavelength study of the IRAS Deep Survey galaxy sample III.
  Spectral classification and dynamical properties
  The infrared deep sample (IDS), in the north ecliptical polar region (NEPR),
is the first complete, far--IR selected sample, on which numerous studies of
galaxy evolution are based. Here we present and analyze the spectral
classification of several galaxies in the IDS sample together with rotation
curves which allow estimating the lower mass limits of a subsample of objects.
We measured fluxes and intensity ratios of the emission lines in the visible
region of the spectrum (lambda 4000-9000 A) for 75 galaxy members. Moreover,
for some of them (55%), the spectra obtained with the Keck II telescope have
sufficient wavelength and spatial resolution to derive their rotation curve.
These galaxies turn out to be disk like systems, with a high fraction (~50%) of
interacting systems. The spectroscopic classification of 42 galaxies, using the
emission-line ratio diagnostic diagrams, shows that the NEPR sample is
predominantly composed of starburst galaxies (71%), while the fraction of AGNs
(7%) and LINERs (21%) is small. The dynamical analysis allows us to estimate
the lower mass limits of 39 galaxies. The rest-frame FIR luminosity
distribution of these galaxies spans the same range as that of the FIR selected
complete sample, i.e. three orders of magnitude, with the same mean value,
log(L_FIR)=10.2. This emphasizes that such galaxies represent FIR properties of
the whole sample well. Moreover, their optical properties are typical of the
sample itself since 62% of these belong to the 60mu selected complete sample.
