  We present a detailed comparison of the CO(3-2) emitting molecular gas
between a local sample of luminous infrared galaxies (U/LIRGs) and a high
redshift sample that comprises submm selected galaxies (SMGs), quasars, and
Lyman Break Galaxies (LBGs). The U/LIRG sample consists of our recent CO(3-2)
survey using the Submillimeter Array while the CO(3-2) data for the high
redshift population are obtained from the literature. We find that the
L(CO(3-2)) and L(FIR) relation is correlated over five orders of magnitude,
which suggests that the molecular gas traced in CO(3-2) emission is a robust
tracer of dusty star formation activity. The near unity slope of 0.93 +/- 0.03
obtained from a fit to this relation suggests that the star formation
efficiency is constant to within a factor of two across different types of
galaxies residing in vastly different epochs. The CO(3-2) size measurements
suggest that the molecular gas disks in local U/LIRGs (0.3 - 3.1 kpc) are much
more compact than the SMGs (3 - 16 kpc), and that the size scales of SMGs are
comparable to the nuclear separation (5 - 40 kpc) of the widely separated
nuclei of U/LIRGs in our sample. We argue from these results that the SMGs
studied here are predominantly intermediate stage mergers, and that the wider
line-widths arise from the violent merger of two massive gas-rich galaxies
taking place deep in a massive halo potential.
