Updated Kinematic Constraints on a Dark Disk

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Updated Kinematic Constraints on a Dark Disk

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Title: Updated Kinematic Constraints on a Dark Disk
Author: Kramer, Eric David; Randall, Lisa

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Citation: Kramer, Eric David, and Lisa Randall. 2016. “Updated Kinematic Constraints on a Dark Disk” The Astrophysical Journal 824 (2) (June 20): 116. doi:10.3847/0004-637x/824/2/116.
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Abstract: We update the method of the Holmberg & Flynn (2000) study, including an updated model of the Milky Way’s interstellar gas, radial velocities, an updated reddening map, and a careful statistical analysis, to bound the allowed surface density and scale height of a dark disk. We pay careful attention to the self-consistency of the model, including the gravitational influence of the dark disk on other disk components, and to the net velocity of the tracer stars. We find that the data set exhibits a non-zero bulk velocity in the vertical direction as well as a displacement from the expected location at the Galactic midplane. If not properly accounted for, these features would bias the bound toward low dark disk mass. We therefore perform our analysis two ways. In the first, traditional method, we subtract the mean velocity and displacement from the tracers’ phase space distributions. In the second method, we perform a non-equilibrium version of the HF method to derive a bound on the dark disk parameters for an oscillating tracer distribution. Despite updates in the mass model and reddening map, the traditional method results remain consistent with those of HF2000. The second, non-equilibrium technique, however, allows a surface density as large as 14 M⊙pc−2 (and as small as 0 M⊙pc−2), demonstrating much weaker constraints. For both techniques, the bound on surface density is weaker for larger scale height. In future analyses of Gaia data, it will be important to verify whether the tracer populations are in equilibrium
Published Version: doi:10.3847/0004-637X/824/2/116
Other Sources: http://arxiv.org/abs/1604.01407
Terms of Use: This article is made available under the terms and conditions applicable to Open Access Policy Articles, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#OAP
Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:28265562
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