Astronomy &Astrophysics Letter to the Editor First spectrally-resolved H2 observations towards HH 54

Context. Herschel observations suggest that the H2O distribution in outflows from low-mass stars resembles the H2 emission. It is still unclear which of the different excitation components that characterise the mid- and near-IR H2 distribution is associated with H2O. Aims. The aim is to spectrally resolve the different excitation components observed in the H2 emission. This will allow us to identify the H2 counterpart associated with H2O and finally derive directly an H2O abundance estimate with respect to H2. Methods. We present new high spectral resolution observations of H2 0−0 S(4), 0−0 S(9), and 1−0 S(1) towards HH 54, a bright nearby shock region in the southern sky. In addition, new Herschel/HIFI H2O (212−101) observations at 1670 GHz are presented