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To the Galactic Virial Radius with Hyper Suprime-Cam

Deason, Alis J.; Belokurov, Vasily; Koposov, Sergey E.

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Authors

Vasily Belokurov

Sergey E. Koposov



Abstract

We exploit the exquisite, deep Hyper Suprime-Cam (HSC) imaging data to probe the Galactic halo out to 200 kpc. Using the ~100 square degree, multiband photometry of the first HSC Wide survey data release, we identify blue horizontal branch (BHB) stars beyond 50 kpc in the halo. The presence of the Sagittarius (Sgr) stream in the HSC fields produces a notable excess of stars at the apocenter of the leading arm (~50–60 kpc). For fields excluding Sgr, the BHB counts are consistent with a continuation of a −4 power law from the inner halo. However, we find that the majority of the non-Sgr BHB stars beyond 50 kpc reside in one 27 square degree HSC field called "VVDS." Curiously, this field is located close to the Magellanic plane, and we hypothesize that the excess of stars between 50 and 200 kpc could be associated with distant Magellanic debris. Indeed, without the VVDS, there are very few BHBs in the remaining portions of the Galaxy probed by the HSC. Accordingly, this scarcity of tracers is consistent with a significant decline in stellar density beyond 50 kpc, with a power law of −4 or steeper.

Citation

Deason, A. J., Belokurov, V., & Koposov, S. E. (2018). To the Galactic Virial Radius with Hyper Suprime-Cam. Astrophysical Journal, 852(2), Article 118. https://doi.org/10.3847/1538-4357/aa9d19

Journal Article Type Article
Acceptance Date Nov 22, 2017
Online Publication Date Jan 12, 2018
Publication Date Jan 12, 2018
Deposit Date Feb 8, 2018
Publicly Available Date Feb 8, 2018
Journal Astrophysical Journal
Print ISSN 0004-637X
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 852
Issue 2
Article Number 118
DOI https://doi.org/10.3847/1538-4357/aa9d19

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Copyright Statement
© 2018. The American Astronomical Society. All rights reserved.





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