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Title: Piercing the Milky Way: an all-sky view of the Orphan Stream

Abstract

We view astrometry, broad-band photometry, and variability information from the Data Release 2 of ESA’s Gaia mission (GDR2) to identify members of the Orphan Stream (OS) across the whole sky. The stream is traced above and below the celestial equator and in both Galactic hemispheres, thus increasing its visible length to ~210° equivalent to ~150 kpc in physical extent. Taking advantage of the large number of RR Lyrae stars in the OS, we extract accurate distances and proper motions across the entire stretch of the tidal debris studied. As delineated by the GDR2 RR Lyrae, the stream exhibits two prominent twists in its shape on the sky which are accompanied by changes in the tangential motion. We complement the RR Lyrae maps with those created using GDR2 Red Giants and the DECam Legacy Survey Main Sequence Turn-Off stars. The behaviour of the OS track on the sky is consistent across all three tracers employed. We determine a strong non-zero motion in the across-stream direction for a substantial portion of the stream. Such a misalignment between the debris track and the streaming velocity cannot be reproduced in a static gravitational potential and signals an interaction with a massive perturber.

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3]; ORCiD logo [4]; ORCiD logo [5];  [6]; ORCiD logo [7]; ORCiD logo [8];  [9]; ORCiD logo [10];  [11];  [11];  [12];  [13];  [14];  [15]
  1. Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, USA; Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, 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. Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510, USA; Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA
  4. Departamento de Astronomía, Instituto de Física, Universidad de la República, Iguá 4225, CP 11400 Montevideo, Uruguay
  5. Department of Physics, University of Surrey, Guildford GU2 7XH, UK
  6. IPAC, Mail Code 314-6, Caltech, 1200 E. California Blvd., Pasadena, CA 91125, USA
  7. Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario M5S 3H4, Canada
  8. Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA
  9. Department of Physics and Astornomy, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2, Canada
  10. Department of Astronomy, The University of Texas at Austin, 2515 Speedway Boulevard, Austin, TX 78712, USA
  11. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
  12. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
  13. Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195, USA
  14. Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904, USA
  15. Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2, Canada
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Org.:
The OATs: Orphan Aspen Treasury Collaboration
OSTI Identifier:
1513284
Report Number(s):
FERMILAB-PUB-18-772-AE; arXiv:1812.08172
Journal ID: ISSN 0035-8711; 1734145
Grant/Contract Number:  
AC02-07CH11359
Resource Type:
Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Volume: 485; Journal Issue: 4; Journal ID: ISSN 0035-8711
Publisher:
Royal Astronomical Society
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; Galaxy: halo; Galaxy: kinematics and dynamics; Galaxy: structure; galaxies: dwarf; galaxies: structure

Citation Formats

Koposov, S. E., Belokurov, V., Li, T. S., Mateu, C., Erkal, D., Grillmair, C. J., Hendel, D., Price-Whelan, A. M., Laporte, C. F. P., Hawkins, K., Sohn, S. T., del Pino, A., Evans, N. W., Slater, C. T., Kallivayalil, N., and Navarro, J. F. Piercing the Milky Way: an all-sky view of the Orphan Stream. United States: N. p., 2019. Web. doi:10.1093/mnras/stz457.
Koposov, S. E., Belokurov, V., Li, T. S., Mateu, C., Erkal, D., Grillmair, C. J., Hendel, D., Price-Whelan, A. M., Laporte, C. F. P., Hawkins, K., Sohn, S. T., del Pino, A., Evans, N. W., Slater, C. T., Kallivayalil, N., & Navarro, J. F. Piercing the Milky Way: an all-sky view of the Orphan Stream. United States. doi:10.1093/mnras/stz457.
Koposov, S. E., Belokurov, V., Li, T. S., Mateu, C., Erkal, D., Grillmair, C. J., Hendel, D., Price-Whelan, A. M., Laporte, C. F. P., Hawkins, K., Sohn, S. T., del Pino, A., Evans, N. W., Slater, C. T., Kallivayalil, N., and Navarro, J. F. Wed . "Piercing the Milky Way: an all-sky view of the Orphan Stream". United States. doi:10.1093/mnras/stz457.
@article{osti_1513284,
title = {Piercing the Milky Way: an all-sky view of the Orphan Stream},
author = {Koposov, S. E. and Belokurov, V. and Li, T. S. and Mateu, C. and Erkal, D. and Grillmair, C. J. and Hendel, D. and Price-Whelan, A. M. and Laporte, C. F. P. and Hawkins, K. and Sohn, S. T. and del Pino, A. and Evans, N. W. and Slater, C. T. and Kallivayalil, N. and Navarro, J. F.},
abstractNote = {We view astrometry, broad-band photometry, and variability information from the Data Release 2 of ESA’s Gaia mission (GDR2) to identify members of the Orphan Stream (OS) across the whole sky. The stream is traced above and below the celestial equator and in both Galactic hemispheres, thus increasing its visible length to ~210° equivalent to ~150 kpc in physical extent. Taking advantage of the large number of RR Lyrae stars in the OS, we extract accurate distances and proper motions across the entire stretch of the tidal debris studied. As delineated by the GDR2 RR Lyrae, the stream exhibits two prominent twists in its shape on the sky which are accompanied by changes in the tangential motion. We complement the RR Lyrae maps with those created using GDR2 Red Giants and the DECam Legacy Survey Main Sequence Turn-Off stars. The behaviour of the OS track on the sky is consistent across all three tracers employed. We determine a strong non-zero motion in the across-stream direction for a substantial portion of the stream. Such a misalignment between the debris track and the streaming velocity cannot be reproduced in a static gravitational potential and signals an interaction with a massive perturber.},
doi = {10.1093/mnras/stz457},
journal = {Monthly Notices of the Royal Astronomical Society},
number = 4,
volume = 485,
place = {United States},
year = {2019},
month = {2}
}

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