Herschel/HIFI observations of water from the intermediate mass protostar NGC 7129 FIRS 2 provide a powerful diagnostic of the physical conditions in this star formation environment. Six spectral settings, covering four H216O and two H218O lines, were observed and all but one H218O line were detected. The four H216O lines discussed here share a similar morphology: a narrower, ≈6 km s-1, component centered slightly redward of the systemic velocity of NGC 7129 FIRS 2 and a much broader, ≈25 km s-1 component centered blueward and likely associated with powerful outflows. The narrower components are consistent with emission from water arising in the envelope around the intermediate mass protostar, and the abundance of H2O is constrained to ≈10-7 for the outer envelope. Additionally, the presence of a narrow self-absorption component for the lowest energy lines is likely due to self-absorption from colder water in the outer envelope. The broader component, where the H2O/CO relative abundance is found to be ≈0.2, appears to be tracing the same energetic region that produces strong CO emission at high J.
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Appendix (page 6) is only available in electronic form at
