The total mass of the Large Magellanic Cloud from its perturbation on the Orphan stream

By D. Erkal, V. Belokurov, C. Laporte, Sergey E. Koposov, T. Li, C. Grillmair, N. Kallivayalil, Adrian M. Price-Whelan, N. Evans II, K. Hawkins and 6 more. Monthly notices of the Royal Astronomical Society, 2018

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In a companion paper by Koposov et al., RR Lyrae from Gaia Data Release 2 are used to demonstrate that stars in the Orphan stream have velocity vectors significantly misaligned with the stream track, suggesting that it has received a large gravitational perturbation from a satellite of the Milky Way. We argue that such a mismatch cannot arise due to any realistic static Milky Way potential and then explore the perturbative effects of the Large Magellanic Cloud (LMC). We find that the LMC can produce precisely the observed motion-track mismatch and we therefore use the Orphan stream to measure the mass of the Cloud. We simultaneously fit the Milky Way and LMC potentials and infer that a total LMC mass of 1.38+0.27−0.24×1011M⊙ is required to bend the Orphan Stream, showing for the first time that the LMC has a large and measurable effect on structures orbiting the Milky Way. This has far-reaching consequences for any technique which assumes that tracers are orbiting a static Milky Way. Furthermore, we measure the Milky Way mass within 50 kpc to be 3.80+0.14−0.11×1011M⊙⁠. Finally, we use these results to predict that, due to the reflex motion of the Milky Way in response to the LMC, the outskirts of the Milky Way’s stellar halo should exhibit a bulk, upwards motion.

Subfields: Astronomy and Astrophysics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/12ecac50b69e29dd7a5fdbbcc227d0bec4bbffe2

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Citations in the corpus

Milky Way Satellite Census. II. Galaxy–Halo Connection Constraints Including the Impact of the Large Magellanic Cloud (2019, result): “…analogs in these two simulations have present-day virial masses of 1.6 and 2.4× 1011 M respectively, consistent with LMC mass estimates based on stellar stream dynamics, satellite dynamics, and the orbital histories of both Magellanic Clouds (Besla 2015; Erkal et al. 2019; Erkal & Belokurov 2019).”
The Zwicky Transient Facility Catalog of Periodic Variable Stars (2020, methodology): “In the Milky Way halo, RR Lyrae are used to trace dwarf galaxies and distant substructures (Drake et al. 2013; Sesar et al. 2017; Medina et al. 2018; Mart́ınez-Vázquez et al. 2019; Erkal et al. 2019).”
The Spur and the Gap in GD-1: Dynamical Evidence for a Dark Substructure in the Milky Way Halo (2018, background): “…considerations imply that the LMC is very massive (∼1011Me; e.g., Kallivayalil et al. 2013; Gómez et al. 2015; Peñarrubia et al. 2016) and has already been invoked to explain deviations from the expected stream tracks of the TucanaIII and Orphan streams (Erkal et al. 2018, 2019, respectively).”