AAS 206th Meeting, 29 May - 2 June 2005
Session 49 Dark Matter and Dark Energy
Poster, Wednesday, 10:00am-7:00pm, Thursday, 9:20am-2:00pm, June 1, 2005, Ballroom A

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[49.02] Scalelengths in Dark Matter Halos

E. I. Barnes (University of Minnesota)

We have formulated and tested a hypothesis regarding the origin of the scalelength present in halos formed in cosmological N-body simulations. We suggest that the radial orbit instability is present in the halos. This instability sets up a scalelength at which the velocity distribution changes rapidly from isotropic to radially anisotropic. This scalelength is reflected in the density distribution as a break radius at which the density profile changes character. We have tested this idea by manipulating the input of a semi-analytic model to imitate the radial orbit instability. Without such manipulation, the halo formed is approximated by a single power-law density profile. The halo formed after the changes have been introduced displays a scalelength and dual power-law density distribution similar to those seen in N-body simulations. This work has been supported by an NSF Astronomical Sciences grant.

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© 2005. The American Astronomical Soceity.