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 60
$lesssim,D_{odot},lesssim$ 100 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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