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

Journal Article · Fri May 17 00:00:00 EDT 2019 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/stz1371· OSTI ID:1556967

Erkal, D.  ^[1]; Belokurov, V.  ^[2]; Laporte, C. F. P. ^[3]; Koposov, S. E.  ^[4]; Li, T. S. ^[5]; Grillmair, C. J. ^[6]; Kallivayalil, N. ^[7]; Price-Whelan, A. M. ^[8]; Evans, N. W. ^[9]; Hawkins, K.  ^[10]; Hendel, D.  ^[11]; Mateu, C.  ^[12]; Navarro, J. F. ^[13]; del Pino, A. ^[14]; Slater, C. T. ^[15]; Sohn, S. T. ^[14]

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1. Department of Physics, University of Surrey, Guildford GU2 7XH, UK
2. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK; Center for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY 10010, USA
3. Department of Physics and Astornomy, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2, Canada
4. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK; Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, USA
5. Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510, USA; Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA
6. IPAC, Mail Code 314-6, Caltech, 1200 E. California Blvd., Pasadena, CA 91125, USA
7. Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904, USA
8. Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA
9. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
10. Department of Astronomy, The University of Texas at Austin, 2515 Speedway Boulevard, Austin, TX 78712, USA
11. Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada
12. Departamento de Astronomía, Instituto de Física, Universidad de la República, Iguá 4225, CP 11400 Montevideo, Uruguay
13. Department of Physics, University of Surrey, Guildford GU2 7XH, UK; Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2, Canada
14. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
15. Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195, USA

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 |$$1.38^{+0.27}_{-0.24} \times 10^{11}\, \rm {M_\odot}$$| 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 |$$3.80^{+0.14}_{-0.11}\times 10^{11} \, \mathrm{M}_\odot$$|. 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.

• Research Organization: Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP)
• Grant/Contract Number: AC02-07CH11359
• OSTI ID: 1556967
• Report Number(s): arXiv:1812.08192; FERMILAB-PUB-18-780-AE; oai:inspirehep.net:1746420
• Journal Information: Monthly Notices of the Royal Astronomical Society, Vol. 487, Issue 2; ISSN 0035-8711
• Publisher: Royal Astronomical Society
• Country of Publication: United States
• Language: English

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79 ASTRONOMY AND ASTROPHYSICS