The escape velocity curve of the Milky Way in Modified Newtonian dynamics
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We determine the escape velocity from the Milky Way (MW) at a range of Galactocentric radii in the context of Modified Newtonian Dynamics (MOND). Due to its non-linear nature, escape is possible if the MW is considered embedded in a constant external gravitational field (EF) from distant objects. We model this situation using a fully self-consistent method based on a direct solution of the governing equations out to several thousand disk scale lengths. We try out a range of EF strengths and mass models for the MW in an attempt to match the escape velocity measurements of Williams et al. (2017). A reasonable match is found if the EF on the MW is ∼0.03a0, towards the higher end of the range considered. Our models include a hot gas corona surrounding the MW, but our results suggest that this should have a very low mass of ∼2 × 1010M⊙ to avoid pushing the escape velocity too high. Our analysis favours a slightly lower baryonic disk mass than the ∼7 × 1010M⊙ required to explain its rotation curve in MOND. However, given the uncertainties, MOND is consistent with both the locally measured amplitude of the MW rotation curve and its escape velocity over Galactocentric distances of 8−50 kpc.
Banik , I & Zhao , H 2018 , ' The escape velocity curve of the Milky Way in Modified Newtonian dynamics ' Monthly Notices of the Royal Astronomical Society , vol 473 , no. 1 , pp. 419-430 . DOI: 10.1093/mnras/stx2350
Monthly Notices of the Royal Astronomical Society
© 2017, the Authors. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at academic.oup.com / https://doi.org/10.1093/mnras/stx2350
IB is supported by Science and Technology Facilities Council studentship 1506672.
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