Stellar Velocity Dispersion in Mergers: The Effects of Dust and Star
  Formation
  We investigate the effects of stellar evolution and dust on measurements of
stellar velocity dispersion in mergers of disk galaxies. $N$-body simulations
and radiative transfer analysis software are used to obtain mass-weighted and
flux-weighted measurements of stellar velocity dispersion. We find that the
distribution of dust with respect to the distribution of young stars in such
systems is more important than the total degree of attenuation. The presence of
dust typically causes flux-weighted measurements of stellar velocity dispersion
to be elevated with respect to mass-weighted measurements because dust
preferentially obscures young stars, which tend to be dynamically cooler than
older stellar populations in such systems. In exceptional situations, in which
young stars are not preferentially obscured by dust, flux-weighted velocity
dispersion measurements tend to be negatively offset with respect to
mass-weighted measurements because the dynamically cool young stellar
populations are more luminous, per unit mass, than older stellar populations.
Our findings provide a context for comparing observationally-obtained
measurements of velocity dispersion with measurements of velocity dispersion
obtained from galaxy merger simulations.
