Forming Young and Hypervelocity Stars in the Galactic Centre via Tidal
  Disruption of a Molecular Cloud
  The Milky Way Galaxy hosts a four million solar mass black hole, Sgr A*, that
underwent a major accretion episode approximately 3-6 Myr ago. During the
episode, hundreds of young massive stars formed in a disc orbiting Sgr A* in
the central half parsec. The recent discovery of a hypervelocity star S5-HVS1,
ejected by Sgr A* five Myr ago with a velocity vector consistent with the disc,
suggests that this event also produced binary star disruptions. The initial
stellar disc has to be rather eccentric for this to occur. Such eccentric disks
can form from the tidal disruptions of molecular clouds. Here we perform
simulations of such disruptions, focusing on gas clouds on rather radial
initial orbits. As a result, stars formed in our simulations are on very
eccentric orbits ($\bar{e}\sim 0.6$) with a lopsided configuration. For some
clouds counter-rotating stars are formed. As in previous work, we find that
such discs undergo a secular gravitational instability that leads to a moderate
number of particles obtaining eccentricities of 0.99 or greater, sufficient for
stellar binary disruption. We also reproduce the mean eccentricity of the young
disk in the Galactic centre, though not the observed surface density profile.
We discuss missing physics and observational biases that may explain this
discrepancy. We conclude that observed S-stars, hypervelocity stars, and disc
stars tightly constrain the initial cloud parameters, indicating a cloud mass
between a few$\times 10^4$ and $10^5 M_{\odot}$, and a velocity between $\sim
40$ and 80 km s$^{-1}$ at 10 pc.
