Thermal H₂O emission from the Herbig-Haro flow HH 54

The first detection of thermal water emission from a Herbig-Haro object is presented. The observations were performed with the LWS (Long Wavelength Spectrograph) aboard ISO (Infrared Space Observatory). Besides H2O, rotational lines of CO are present in the spectrum of HH 54. These high-J CO lines are used to derive the physical model parameters of the FIR (far-infrared) molecular line emitting regions. This model fits simultaneously the observed OH and H2O spectra for an OH abundance X(OH)=10-6 and a water vapour abundance X(H2O)=10-5. At a distance of 250pc, the total CO, OH and H2O rotational line cooling rate is estimated to be 1.3x10-2 L⊙, which is comparable to the mechanical luminosity generated by the 10km s-1 shocks, suggesting that practically all of the cooling of the weak-shock regions is done by these three molecular species alone

Thermal H_2_O emission from the Herbig-Haro flow HH 54.

The first detection of thermal water emission from a Herbig-Haro object is presented. The observations were performed with the Lws (Long Wavelength Spectrograph) aboard Iso (Infrared Space Observatory). Besides H_2_O, rotational lines of CO are present in the spectrum of HH 54. These high-J CO lines are used to derive the physical model parameters of the Fir (far-infrared) molecular line emitting regions. This model fits simultaneously the observed OH and H_2_O spectra for an OH abundance X(OH)=10^-6^ and a water vapour abundance X(H_2_O)=10^-5^. At a distance of 250pc, the total CO, OH and H_2_O rotational line cooling rate is estimated to be 1.3x10^-2^Lsun_, which is comparable to the mechanical luminosity generated by the 10km/s shocks, suggesting that practically all of the cooling of the weak-shock regions is done by these three molecular species alone