Kavli Affiliate: Masahiro Takada
| First 5 Authors: Yoshihisa Suzuki, Masashi Chiba, Yutaka Komiyama, Kohei Hayashi, Masayuki Tanaka
| Summary:
We analyze the photometric data in the Wide layer of the Hyper Suprime-Cam
Subaru Strategic Program (HSC-SSP) over $sim 1,200$ deg$^{2}$ to uncover new
halo substructures beyond the distance, $D_{odot}sim$ 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 the new overdensity toward Bo"otes at about
$D_{odot}sim$ 60 kpc and the new stream-like feature toward Pisces at around
$D_{odot}sim$ 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.
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