Thermal H₂O emission from the Herbig-Haro flow HH 54

R.Liseau- C.Ceccarelli - B.Larsson - B.Nisini - G.J.White - P.Ade - C.Armand - M.Burgdorf - E.Caux - R.Cerulli - S.Church - P.E.Clegg - A.DiGorgio - I.Furniss - T.Giannini - W.Glencross - C.Gry - K.King - T.Lim - D.Lorenzetti - S.Molinari - D.Naylor - R.Orfei - P.Saraceno - S.Sidher - H.Smith - L.Spinoglio - B.Swinyard - D.Texier - E.Tommasi - N.Trams - S.Unger

Abstract:

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 HH54. 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^-3.

At a distance of 250pc, the total CO, OH and H₂O rotational line cooling rate is estimated to be 1.310 L_solar,which is comparable to the mechanical luminosity generated by the 10kms^-1 shocks, suggesting that practically all of the cooling of the weak-shock regions is done by these three molecular species alone.

Keywords:
Stars: formation - ISM: molecules - ISM: jets and outflows - ISM: individual objects: HH54 - Physical processes: Shock waves - Physical processes: Radiative transfer

Full text