An investigation of the B335 region through far infrared spectroscopy withISO

We present far infrared spectra of the B335 dark cloud region, obtained wit h the Long Wavelength Spectrometer (LWS) on-board the ISO satellite. Deep s pectra were obtained towards the far infrared outflow exciting source, loca ted in the B335 core, and on the three associated Herbig Hare (HH) objects HH119 A, B and C. In addition, a region of about 9' in RA and 4' in Dec. wa s mapped which covers the whole molecular outflow. [CII] 158 mu m emission was found to be uniformly distributed across the ob served region, with the intensity expected for a photodissociation region e xcited by the average interstellar held. The [OI]63 mu m emission was detec ted only towards two out of the three HH objects and from the B335 FIR sour ce; excitation from the high-velocity shocks responsible for the HH119 knot s can account for the observed line intensity. CO line emission from the ro tational levels J=15 to J=18 was detected only towards B335 FIR and can be modelled as arising in warm gas whose excitation temperature is in the rang e 150-800 K, located in a compact(similar to 10(-3) pc) and dense (n(H2) si milar to 10(6) cm(-3)) region. If we assume that the CO J= 6-->5 line obser ved from the ground is also emitted from the same gas component, we derive for this component a temperature of 350 K and a density of 5.10(5) cm(-3). Current collapse models for the B335 core fail to predict the presence of s uch warm gas in the infalling source envelope, at the spatial scales implie d by our model fit. It is likely that the molecular emission is excited in a low-velocity ( upsilon similar to 10 km s(-1)) non-dissociative-shock, or iginating at the base of the flow.