Velocity-resolved hot water emission detected toward HL Tau with the
  Submillimeter Array
  Using the Submillimeter Array (SMA) on Mauna Kea, the H2-16O 10_2,9-9_3,6
transition (E_up=1863K) at 321.2 GHz has been detected toward the embedded
low-mass protostar HL Tau. The line centroid is blue-shifted by 15 km/s with
respect to the source velocity, and it has a FWHM of 20 km/s. The emission is
tentatively resolved and extends ~3-4" over the sky (~2 beams), or ~500 AU at
the distance of Taurus. The velocity offset, and to a lesser degree the spatial
extent of the emission, shows that the line originates in the protostellar jet
or wind. This result suggests that at least some water emission observed toward
embedded sources, and perhaps also disk sources, with Herschel and Spitzer
contains a wind or jet component, which is crucial for interpreting these data.
These pathfinder observations done with the SMA opens a new window to studying
the origin of water emission with e.g. ALMA, thus providing new insights into
where water is in protostellar systems.
