Unveiling the Sigma-Discrepancy in IR-Luminous Mergers I: Dust &
  Dynamics
  Mergers in the local universe present a unique opportunity for studying the
transformations of galaxies in detail. Presented here are recent results, based
on multi-wavelength, high-resolution imaging and medium resolution
spectroscopy, which demonstrate how star-formation and the presence of Red
Supergiants and/or Asymptotic Giant Branch stars has lead to a serious
underestimation of the dynamical masses of infrared-bright galaxies. The
dominance of a nuclear disk of young stars in the near-infrared bands, where
dust obscuration does not block their signatures, can severely bias the global
properties measured in a galaxy, including mass. This explains why past studies
of gas-rich Luminous & Ultraluminous Infrared Galaxies, which have measured
dynamical masses using the 1.62 or 2.29 micron CO band-heads, have found that
these galaxies are forming m < m* ellipticals. On the other hand, precisely
because of dust obscuration, I-band photometry and central velocity dispersions
obtained with the Calcium II triplet at 0.85 microns reflect the global
properties of the mergers and suggest that all types of merger remnants,
including infrared-bright ones, will form m > m* ellipticals. Moreover, merger
remnants, including LIRGs, are placed on the I-band Fundamental Plane for the
first time and appear to be virtually indistinguishable from elliptical
galaxies.
