https://orcid.org/0009-0009-9769-534X
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Yoshihisa Suzuki, Masashi Chiba, Yutaka Komiyama, Kohei Hayashi, Masayuki Tanaka, Tetsuya Fukushima, Scott G Carlsten, Akira Tokiwa, Tian Qiu, Masahiro Takada, The Milky Way tomography with Subaru Hyper Suprime-Cam. I. Halo substructures, Publications of the Astronomical Society of Japan, Volume 76, Issue 2, April 2024, Pages 205–218, https://doi.org/10.1093/pasj/psae003
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Abstract
We analyze the photometric data in the Wide layer of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) over ∼1200 deg2 to uncover new halo substructures beyond the distance, D⊙ ∼ 30 kpc, from the Sun. For this purpose, we develop an isochrone filter for an old, metal-poor stellar system to extract the faint main-sequence stars at a range of distances. With this method, we detect not only the previously discovered substructures such as the Orphan Stream, but also a new overdensity toward Boötes at about D⊙ ∼ 60 kpc and a new stream-like feature toward Pisces at around D⊙ ∼ 60 kpc. It has been suggested that a small-scale overdensity exists in this direction of Pisces (the so-called Pisces Overdensity), but our results show that the overdensity is widely spread with a tidally elongated feature. Combining our results with the ongoing Hyper Suprime-Cam narrow-band survey and the near-future spectroscopic survey with Prime Focus Spectrograph (PFS) will allow us to place strong constraints on the origin of these halo substructures.
