Mathematics – Logic
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004sf2a.conf..691m&link_type=abstract
SF2A-2004: Semaine de l'Astrophysique Francaise, meeting held in Paris, France, June 14-18, 2004. Edited by F. Combes, D. Barret
Mathematics
Logic
Scientific paper
Density profiles (NFW and similar) of structures found in cosmological ΛCDM N-body simulations cannot represent the total matter distribution in elliptical galaxies, or else their local mass-to-light ratio would be smaller than the value expected from the stellar component, and also their central velocity dispersions averaged within a circular aperture or thin slit would be lower than expected from what is observed through the Faber-Jackson relation. This implies that the stellar component dominates in the observed regions of ellipticals and it is therefore more difficult to reject the hypothesis that elliptical galaxies have a dark matter component similar to what is observed in the cosmological simulations or to infer the inner slope of the dark matter density profile. One must measure line-of-sight velocity dispersions out to 5 effective radii and with 15 km/s accuracy to infer the dark matter content within a factor of 3 inside the virial radius. The new density profile and slight radial orbit anisotropy found in recent cosmological simulations imply that, for a given M/L within the virial radius, the line of sight velocity dispersions at 5 effective radii are smaller than inferred with NFW dark matter and isotropic orbits, and conversely, the low velocity dispersions recently measured at 5 effective radii for the planetary nebulae around ellipticals are explained by global mass-to-light ratios within the virial radius that are twice as large as inferred when the dark matter is supposed NFW and the orbits isotropic.
Lokas Ewa L.
Mamon Gary A.
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