  Since the near future should see a rapidly expanding set of probes of the
halo masses of individual early-type galaxies, we introduce a convenient
parameter for characterising the halo masses from both observational and
theoretical results: \dML, the logarithmic radial gradient of the mass-to-light
ratio. Using halo density profiles from LCDM simulations, we derive predictions
for this gradient for various galaxy luminosities and star formation
efficiencies $\epsilon_{SF}$. As a pilot study, we assemble the available \dML\
data from kinematics in early-type galaxies - representing the first unbiassed
study of halo masses in a wide range of early-type galaxy luminosities - and
find a correlation between luminosity and \dML, such that the brightest
galaxies appear the most dark-matter dominated. We find that the gradients in
most of the brightest galaxies may fit in well with the LCDM predictions, but
that there is also a population of fainter galaxies whose gradients are so low
as to imply an unreasonably high star formation efficiency $\epsilon_{SF} > 1$.
This difficulty is eased if dark haloes are not assumed to have the standard
LCDM profiles, but lower central concentrations.

Astrophysics