The interstellar medium - new results from Herschel
by
Carina Persson(Chalmers, Earth and Space Sciences)
→
Europe/Stockholm
FA31
FA31
Description
The study of diffuse and translucent interstellar clouds has taken a major leap forward with the launch of the Herschel Space Observatory. The environment in these clouds is very harsh and existing species are therefore small molecules, mostly light hydrides. These species are, however, very difficult to observe since they have their ground state transitions at wavelengths which normally are not accessible using ground-based facilities. With Herschel, new opportunities opened for spectrally resolved observations of key species, e.g. HF, H2O, H3O+, H2O+, OH+, CH, CH+, HCl, HCl+, NH, NH2, and NH3, with high sensitivity.
We use compact far-infrared submm-wave sources in star-forming regions as background continuum for absorption measurements of ground-state transitions in the diffuse line-of-sight clouds. These observations have shed new light on the production pathways and the physical conditions in the interstellar gas. The focus of this talk is on the analysis of the nitrogen hydrides. All detected rotational transitions show a complex pattern of hyperfine structure components. We find emission and absorption associated directly with the hot-core sources themselves, absorption by foreground material and from gas with inward motion towards two sources. We also investigate the ortho-to-para ratios (OPR) of NH2 and NH3 in both the diffuse line-of-sight gas and in the warm and dense cores. Surprisingly low NH2 and NH3 OPR is found in contradiction to their expected values. Deep searches for the so far undetected species NH+ and NH2- have been performed without success which suggest very low abundances.
