Astronomy and Astrophysics Letters dedicated to ISO

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


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 Lsolar,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.

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

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