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Mass-to-light ratio gradients in early-type galaxy haloes
Monthly Notices of the Royal Astronomical Society (2005)
  • N. R. Napolitano
  • M. Capaccioli
  • Aaron J. Romanowsky, San Jose State University
  • N. G. Douglas
  • M. R. Merrifield, University of Nottingham
  • K. Kuijken
  • M. Arnaboldi
  • O. Gerhard
  • K. C. Freeman

Owing 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 εSF. 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 εSF > 1. This difficulty is eased if dark haloes are not assumed to have the standard ΛCDM profiles, but lower central concentrations.

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Copyright © 2005 Oxford University Press. The published article may be found at :
Citation Information
N. R. Napolitano, M. Capaccioli, Aaron J. Romanowsky, N. G. Douglas, et al.. "Mass-to-light ratio gradients in early-type galaxy haloes" Monthly Notices of the Royal Astronomical Society Vol. 357 (2005)
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