Friday, March 1, 2013

1302.7097 (Shigeki Inoue et al.)

Astrometric mock observations for determining the local dark matter density    [PDF]

Shigeki Inoue, Naoteru Gouda
To determine the local dark matter density around the solar system is a classical problem in astronomy. Recently, Garbari et al. have devised a novel method to determine the local dark matter density from stellar distribution and vertical velocity dispersion profiles perpendicular to the Galactic plane. Their method has the advantages of abolishing conventional approximations and using only a few assumptions. Their determinations, however, preferred relatively high dark matter densities. The first aim of this paper is to carefully scrutinize the their method. The second aim is to examine influences by observational uncertainties. To examine the influences by the observational imprecision, we create mock observation data for stars being dynamical tracers based on an analytical galaxy model and apply parametrized observational errors to the mock data. We evaluate the accuracy of determining the dark matter density by applying the Garbari et al. method to the mock data. In addition, we estimate a sample size and observational precisions to determine the dark matter density with accuracy. We find that the Garbari et al. method is capable of determining the local dark matter density with accuracy if the sample size and observational precisions are satisfactory. However, the parallax and proper motion errors can cause overestimation of the dark matter density. We estimate the required precisions of the parallax measurements to be 0.1-0.3 mas. Also, we find that the line-of-sight velocity errors can cause either underestimation or overestimation of the dark matter density. From these results, we infer that Garbari et al. would be overestimating the local dark matter density due to use of imprecise data from the Hipparcos catalog. We expect that Gaia will provide data precise enough to determine the local dark matter density using the Garbari et al. method.
View original: http://arxiv.org/abs/1302.7097

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