On the spatial distribution and the origin of hypervelocity stars
  Hypervelocity stars (HVSs) escaping away from the Galactic halo are dynamical
products of interactions of stars with the massive black hole(s) (MBH) in the
Galactic Center (GC). They are mainly B-type stars with their progenitors
unknown. OB stars are also populated in the GC, with many being hosted in a
clockwise-rotating young stellar (CWS) disk within half a parsec from the MBH
and their formation remaining puzzles. In this paper, we demonstrate that HVSs
can well memorize the injecting directions of their progenitors using both
analytical arguments and numerical simulations, i.e., the ejecting direction of
an HVS is almost anti-parallel to the injecting direction of its progenitor.
Therefore, the spatial distribution of HVSs maps the spatial distribution of
the parent population of their progenitors directly. We also find that almost
all the discovered HVSs are spatially consistent with being located on two thin
disk planes. The orientation of one plane is consistent with that of the
(inner) CWS disk, which suggests that most of the HVSs originate from the CWS
disk or a previously existed disk-like stellar structure with an orientation
similar to it. The rest of HVSs may be correlated with the plane of the
northern arm of the mini-spiral in the GC or the plane defined by the outer
warped part of the CWS disk. Our results not only support the GC origin of HVSs
but also imply that the central disk (or the disk structure with a similar
orientation) should persist or be frequently rejuvenated over the past 200 Myr,
which adds a new challenge to the stellar disk formation and provides insights
to the longstanding problem of gas fueling into massive black holes.
