The velocity dispersion gives to some
approximation the scale for the
specific kinetic energy contained in in un-ordered motions and combined
the velocity of rotation it may give an estimate of the specific
energy. For early-type galaxies (E-S0) it is one of the parameters
in the Fundamental-Plane relation, which reflects the self-similarity
all early-type galaxies and their equilibrium status.
The velocity dispersions are standardized to an aperture rnorm of 0.595 h-1kpc, which is equivalent to an angular diameter of 3.4 arcsec at the distance of Coma. The method of normalization is the one introduced by Jorgensen et al:
vdisc = vdis . [rmeas/rnorm]0.04 ,
where rmeas is the aperture defined by the slit width at the distance of the object. All raw vdis values are rescaled to the homogeneous system and thus corrected for systematic effects on the individual datasets (see Golev & Prugniel, 1998). At the end of 2003, the total available catalog contains 8596 measurements of vdis for 3636 galaxies
This parameter is used to determine the distance modulus mod0.