Mathematics – Logic
Scientific paper
Jan 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21333505f&link_type=abstract
American Astronomical Society, AAS Meeting #213, #335.05; Bulletin of the American Astronomical Society, Vol. 41, p.397
Mathematics
Logic
Scientific paper
Our current picture of the universe says that galaxies are surrounded by massive dark matter halos in which they formed. Cosmological simulations have become detailed enough to model individual galaxy formation, yet observational signatures of dark matter in elliptical galaxies are still difficult to measure. Tracers, such as planetary nebulae, have been used to probe the outer parts of galaxies where dark matter is thought to dominate. We present line-of-sight velocity distributions of individual elliptical galaxies obtained with long-slit spectroscopy from the Hobby-Eberly Telescope. We find that in the case of NGC 821 these stellar velocity dispersions are larger than planetary nebulae measurements at large radii. We then use axisymmetric orbit-superposition models to match possible dark matter distributions to our kinematic data. These general models allow us to break the degeneracy between mass and anisotropy in these systems. For NGC 821 we find that dark matter is needed to explain the data, yet the expected NFW profile does not provide the best fit. Early results for NGC 6702 give a similar conclusion.
Forestell Amy Dove
Gebhardt Karl
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