The Herschel-HIFI view of mid-IR quiet massive protostellar objects
  We present Herschel/HIFI observations (WISH KP) of 14 water lines in a small
sample of galactic massive protostellar objects: NGC6334I(N), DR21(OH),
IRAS16272-4837, and IRAS05358+3543. We analyze the gas dynamics from the line
profiles. Through modeling of the observations using RATRAN, we estimate
outflow, infall, turbulent velocities, molecular abundances, and investigate
any correlation with the evolutionary status of each source. The molecular line
profiles exhibit a broad component coming from the shocks along the cavity
walls associated with the protostars, and an infalling (or expansion for
IRAS05358+3543) and passively heated envelope component, with highly supersonic
turbulence likely increasing with the distance from the center. Accretion rates
between 6.3 10^{-5} and 5.6 10^{-4} \msun yr^{-1} are derived from the infall
observed in three of our sources. The outer water abundance is estimated to be
at the typical value of a few 10^{-8} while the inner abundance varies from 1.7
10^{-6} to 1.4 10^{-4} with respect to H2 depending on the source. We confirm
that regions of massive star formation are highly turbulent and that the
turbulence likely increases in the envelope with the distance to the star. The
inner abundances are lower than the expected 10^{-4} perhaps because our
observed lines do not probe deep enough into the inner envelope, or because
photodissociation through protostellar UV photons is more efficient than
expected. We show that the higher the infall/expansion velocity in the
protostellar envelope, the higher is the inner abundance, maybe indicating that
larger infall/expansion velocities generate shocks that will sputter water from
the ice mantles of dust grains in the inner region. High-velocity water must be
formed in the gas-phase from shocked material.
