The Galactic Census of High- and Medium-mass Protostars. II.
  Luminosities and Evolutionary States of a Complete Sample of Dense Gas Clumps
  (Abridged) The Census of High- and Medium-mass Protostars (CHaMP) is the
first large-scale (280 degree<l<300 degree, -4 degree<b<2 degree), unbiased,
sub-parsec resolution survey of Galactic molecular clumps and their embedded
stars. Barnes et al. (2011) presented the source catalog of ~300 clumps based
on HCO+(1-0) emission, used to estimate masses M. Here we use archival
mid-infrared to mm continuum data to construct spectral energy distributions.
Fitting two-temperature grey-body models, we derive bolometric luminosities, L.
We find the clumps have 10Lsun<L<1E6.5Lsun and 0.1<L/M<1E3, consistent with
theoretical expectations of a clump population that spans a range of
instantaneous star formation efficiencies from 0 to ~50%. We thus expect L/M to
be a useful, strongly-varying indicator of clump evolution during the star
cluster formation process. We find correlations of the ratio of warm to cold
component fluxes and of cold component temperature with L/M. We also find a
near linear relation between L/M and Spitzer-IRAC specific intensity (surface
brightness), which may thus also be useful as a star formation efficiency
indicator. The lower bound of the clump $L/M$ distribution suggests the star
formation efficiency per free-fall time is epsilon<0.2. We do not find strong
correlations of L/M with mass surface density, velocity dispersion or virial
parameter. We find a linear relation between L and L_{HCO+(1-0}}, although with
large scatter for any given individual clump. Fitting together with
extragalactic systems, the linear relation still holds, extending over 10
orders of magnitude in luminosity. The complete nature of the CHaMP survey over
a several kiloparsec-scale region allows us to derive a measurement at an
intermediate scale bridging those of individual clumps and whole galaxies.
