Integrated Spectroscopy of the Herschel Reference Survey. The spectral
  line properties of a volume-limited, K-band selected sample of nearby
  galaxies
  We present long-slit integrated spectroscopy of 238 late-type galaxies
belonging to the Herschel Reference Survey, a volume limited sample
representative of the nearby universe. This sample has a unique legacy value
since ideally defined for any statistical study of the multifrequency
properties of galaxies spanning a large range in morphological type and
luminosity. The spectroscopic observations cover the spectral range 3600-6900 A
at a resolution R ~ 1000 and are thus suitable for separating the underlying
absorption from the emission of the Hbeta line as well as the two [NII] lines
from the Halpha emission. We measure the fluxes and the equivalent widths of
the strongest emission lines ([OII], Hbeta, [OIII], [NII], Halpha, and [SII]).
The data are used to study the distribution of the equivalent width of all the
emission lines, of the Balmer decrement C(Hbeta) and of the observed underlying
Balmer absorption under Hbeta in this sample. Combining these new spectroscopic
data with those available at other frequencies, we also study the dependence of
C(Hbeta) and E.W.Hbeta_{abs} on morphological type, stellar mass and stellar
surface density, star formation rate, birthrate parameter and metallicity in
galaxies belonging to different environments (fields vs. Virgo). The
distribution of the equivalent width of all the emission lines, of C(Hbeta) and
E.W.Hbeta_{abs} are systematically different in cluster and field galaxies. The
Balmer decrement increases with stellar mass, stellar surface density,
metallicity and star formation rate of the observed galaxies, while it is
unexpectedly almost independent from the column density of the atomic and
molecular gas. The dependence of C(Hbeta) on stellar mass is steeper than that
previously found in other works. The underlying Balmer absorption does not
significantly change with any of these physical parameters.
