  In order to study the state of gas in galaxies, diagrams of the relation of
optical emission line fluxes are used allowing one to separate main ionization
sources: young stars in the H II regions, active galactic nuclei, and shock
waves. In the intermediate cases, when the contributions of radiation from OB
stars and from shock waves mix, identification becomes uncertain, and the issue
remains unresolved on what determines the observed state of the diffuse ionized
gas (DIG) including the one on large distances from the galactic plane. Adding
of an extra parameter - the gas line-of-sight velocity dispersion - to
classical diagnostic diagrams helps to find a solution. In the present paper,
we analyze the observed data for several nearby galaxies: for UGC 10043 with
the galactic wind, for the star forming dwarf galaxies VII Zw 403 and Mrk 35,
for the galaxy Arp 212 with a polar ring. The data on the velocity dispersion
are obtained at the 6-m SAO RAS telescope with the Fabry-Perot scanning
interferometer, the information on the relation of main emission-line fluxes -
from the published results of the integral-field spectroscopy (the CALIFA
survey and the MPFS spectrograph). A positive correlation between the radial
velocity dispersion and the contribution of shock excitation to gas ionization
are observed. In particular, in studying Arp 212, "BPT-sigma relation" allowed
us to confirm the assumption on a direct collision of gaseous clouds on the
inclined orbits with the main disk of the galaxy.

Astrophysics of Galaxies