Distribution of water in the G327.3-0.6 massive star-forming region
  We aim at characterizing the large-scale distribution of H2O in G327.3-0.6, a
massive star-forming region made of individual objects in different
evolutionary phases. We investigate variations of H2O abundance as function of
evolution. We present Herschel continuum maps at 89 and 179 $\mu$m of the whole
region and an APEX map at 350 {\mu}m of the IRDC. New spectral HIFI maps toward
the IRDC region covering low-energy H2O lines at 987 and 1113 GHz are also
presented and combined with HIFI pointed observations of the G327 hot core. We
infer the physical properties of the gas through optical depth analysis and
radiative transfer modeling. The continuum emission at 89 and 179 {\mu}m
follows the thermal continuum emission at longer wavelengths, with a peak at
the position of the hot core, a secondary peak in the Hii region, and an
arch-like layer of hot gas west of the Hii region. The same morphology is
observed in the 1113 GHz line, in absorption toward all dust condensations.
Optical depths of ~80 and 15 are estimated and correspond to column densities
of 10^15 and 2 10^14 cm-2, for the hot core and IRDC position. These values
indicate an H2O to H2 ratio of 3 10^-8 toward the hot core; the abundance of
H2O does not change along the IRDC with values of some 10^-8. Infall (over ~
20") is detected toward the hot core position with a rate of 1-1.3 10^-2 M_sun
/yr, high enough to overcome the radiation pressure due to the stellar
luminosity. The source structure of the hot core region is complex, with a cold
outer gas envelope in expansion, situated between the outflow and the observer,
extending over 0.32 pc. The outflow is seen face-on and centered away from the
hot core. The distribution of H2O along the IRDC is roughly constant with an
abundance peak in the more evolved object. These water abundances are in
agreement with previous studies in other massive objects and chemical models.
