Napolitano, Nicola RCapaccioli, MassimoRomanowsky, A JDouglas, Nigel GMerrifield, M RKuijken, KonradArnaboldi, MagdaGerhard, OrtwinFreeman, Kenneth2015-12-130035-8711http://hdl.handle.net/1885/80164Owing to the fact that 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 characterizing the halo masses from both observational and theoretical results: ∇ℓΥ, the logarithmic radial gradient of the mass-to-light ratio. Using halo density profiles from Λ-cold dark matter (CDM) simulations, we derive predictions for this gradient for various galaxy luminosities and star formation efficiencies ∈SF. As a pilot study, we assemble the available ∇ℓΥ data from kinematics in early-type galaxies - representing the first unbiased study of halo masses in a wide range of early-type galaxy luminosities - and find a correlation between luminosity and ∇ℓΥ, 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 ΛCDM 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 ∈SF > 1. This difficulty is eased if dark haloes are not assumed to have the standard ΛCDM profiles, but lower central concentrations.Keywords: Dark matter; Galaxies: evolution; Galaxies: fundamental parameters; Galaxies: haloes; Galaxies: kinematics and dynamics200510.1111/j.1365-2966.2005.08683.x2015-12-11