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Session 21 - Galaxies and Clusters of Galaxies.
Oral session, Monday, June 10
Humanities 3650,

[21.08] Rotation Curves of Giant LSB Galaxies

T. E. Pickering, C. D. Impey, J. F. Navarro (Steward Obs.), J. van Gorkom (Columbia U.), G. D. Bothun (U. Oregon)

We present optical and H I rotation curves of a sample of giant, low surface brightness (LSB) galaxies including the prototype, Malin 1. The rotation curves of these diffuse systems are expected to more faithfully reflect the structure of their dark matter halos due to the reduced contribution of the disk to the overall gravitational potential. Indeed, the curves we derive generally exhibit the slowly rising behavior expected for dark matter dominated systems. In several cases, the rotation curves continue to rise out to the last measured points at radii of 50--70 kpc/h_100. By comparison with cosmological N-body simulations such as those of Navarro et al. (1996, in press) the shapes of these curves can be used to constrain cosmological parameters. The results obtained to date indicate that dark matter halos are significantly less concentrated than predicted by the standard CDM cosmogony. Low density models with a cosmological constant appear to be favored by our preliminary results.

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