Cosmological simulations of quasar fueling to sub-parsec scales using
  Lagrangian hyper-refinement
  We present cosmological hydrodynamic simulations of a quasar-mass halo
($M_{\rm halo} \approx 10^{12.5}\,{\rm M}_{\odot}$ at z=2) that for the first
time resolve gas transport down to the inner 0.1 pc surrounding the central
massive black hole. We model a multi-phase interstellar medium including
stellar feedback by supernovae, stellar winds, and radiation, and a
hyper-Lagrangian refinement technique increasing the resolution dynamically
approaching the black hole. We do not include black hole feedback. We show that
the sub-pc inflow rate (1) can reach ~6 M$_{\odot}$yr$^{-1}$ roughly in steady
state during the epoch of peak nuclear gas density (z~2), sufficient to power a
luminous quasar, (2) is highly time variable in the pre-quasar phase, spanning
0.001-10 M$_{\odot}$yr$^{-1}$ on Myr timescales, and (3) is limited to short
(~2 Myr) active phases (0.01-0.1 M$_{\odot}$yr$^{-1}$) followed by longer
periods of inactivity at lower nuclear gas density and late times (z~1), owing
to the formation of a hot central cavity. Inflowing gas is primarily cool,
rotational support dominates over turbulence and thermal pressure, and star
formation can consume as much gas as provided by inflows across 1 pc - 10 kpc.
Gravitational torques from multi-scale stellar non-axisymmetries dominate
angular momentum transport over gas self-torquing and pressure gradients, with
accretion weakly dependent on black hole mass. Sub-pc inflow rates correlate
with nuclear (but decouple from global) star formation and can exceed the
Eddington rate by x10. The black hole can move ~10 pc from the galaxy center on
~0.1 Myr. Accreting gas forms pc-scale, rotationally supported, obscuring
structures often misaligned with the galaxy-scale disk. These simulations open
a new avenue to investigate black hole-galaxy co-evolution.
