Gravitational potential recovery in a realistic halo
with Marla Geha, Andreas Kuepper, Juerg Diemand, Kathryn Johnston and David Hogg
Streams formed in different potentials
Tidal streams are important tools for measuring the total Milky Way mass. In past studies, stellar streams were modeled in smooth and static gravitational potentials. However, real dark matter halos have substructure and are continually evolving by accretion.
We studied a large sample of streams evolved in the Via Lactea II (VL2) simulation, which represents a realistic Galactic halo potential. Our FAST-FORWARD method uses a Markov Chain Monte Carlo algorithm to compare an "observed" stream to models created in trial analytic potentials, which are smooth and static. The recovered potential parameters are in agreement with the best fit to the global, present-day VL2 potential. However, merely assuming an analytic potential limits the dark matter halo mass measurement to an accuracy of 5 to 20%, depending on the choice of analytic parametrization. Mass estimates are progressively worse for streams on orbits closer to the Galactic center, motivating the search for streams at large galactocentric distances.
More information:
Milky Way Mass and Potential Recovery Using Tidal Streams in a Realistic Halo
(ADS | Arxiv)
Bonaca, A., Geha, M., Kuepper, A. H. W., Diemand, J., Johnston, K. V., and Hogg, D. W., 2014, ApJ, 795, 94
Movie:
Illustration of the FAST-FORWARD potential recovery method
Gallery:
Example streams from our VL2 sample (left), and their analytic analogs formed in a parametric potential best-fitting the present-day VL2 (right). All streams have a Palomar 5-like progenitor (large white circle) that has been forming tidal tails for 6 Gyr. The leading tails are shown in warm colors, while the trailing are in cold colors. Stars in blue and red were released first, while green and yellow are the most recently released stream stars.
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