Markov Chain Monte Carlo Modeling of the Tidal Stream of NGC 5466

Stephen Pardy, University of Wisconsin Madison
Advisors: Andreas Kupper

Abstract: The Milky Way's dark matter halo remains poorly understood even in the era of high precision cosmology. Tidal streams have the unique ability to probe the potential field in the outer regions of a galaxy where the dark matter halo dominates. Although globular clusters are quite common, only a few have definite tidal tails that make them good candidates for measure the potential. In this paper we present new models for NGC 5466, a cluster with a tentative 45 degree tidal tail, using recently acquired radial velocity and proper motion data from bright stars in the stream. We model the tidal stream of NGC 5466 using the streakline code (Kupper et al. 2012) and an MCMC technique to efficiently search over a large number of models. We compare models constructed using the data of (Grillmair & Johnson 2006) with those from (Belokurov et al. 2006). Our best models constrain the Milky Way flattening parameter to be nearly 1, indicating a spherical halo, while providing new, tighter constraints for the proper motion of the cluster.

PDF Presentation
Project report