| Name | OT1_dlis_2 |
| Title | Ammonia as a Tracer of the Earliest Stages of Star Formation |
| URL | http://archives.esac.esa.int/hsa/whsa-tap-server/data?retrieval_type=OBSERVATION&observation_id=1342238591&instrument_name=HIFI&product_level=LEVEL0&compress=true |
| DOI | https://doi.org/10.5270/esa-51qg935 |
| Author | lis, d. |
| Description | Stars form in molecular cloud cores, cold and dense regions enshrouded by dust. The initiation of this process is among the least understood steps of star formation. Highresolution heterodyne spectroscopy provides invaluable information about the physical conditions(density, temperature), kinematics (infall, outflows), and chemistry of these regions. Classical molecular tracers, such CO, CS, and many other abundant gasphase species, have been shown to freeze out onto dust grain mantles in prestellar cores. However, Nbearing species, in particular ammonia, are much less affected by depletion and are observed to stay in the gas phase at densities in excess of 1e6 cm3. The molecular freezeout has important consequences for the chemistry of dense gas. In particular, the depletion of abundant gasphase species with heavy atoms drives up abundances of deuterated H3+ isotopologues, which in turn results in spectacular deuteration levels of molecules that do remain in the gas phase. Consequently, lines of deuterated Nbearing species, in particular the fundamental lines of ammonia isotopologues, having very high critical densities, are optimum tracers of innermost regions of dense cores.We propose to study the morphology, density structure and kinematics of cold and dense cloud cores, by mapping the spatial distribution ofammonia isotopologues in isolated dense prestellar cores using Herschel/HIFI. These observations provide optimum probes of the onset of star formation, as well as the physical processes that control gasgrain interaction, freezeout, mantle ejection and deuteration. The sensitive, highresolution spectra acquired within this program will be analyzed using sophisticated radiative transfer models and compared with outputs of stateoftheart 3D MHD simulations and chemical models developed by the members of our team. |
| Publication |
|
| Instrument | HIFI_HifiPoint_fs, HIFI_HifiMapping_fly |
| Temporal Coverage | 2012-02-02T02:01:33Z/2012-09-26T06:34:40Z |
| Version | SPG v14.1.0 |
| Mission Description | Herschel was launched on 14 May 2009! It is the fourth cornerstone mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities. |
| Creator Contact | https://support.cosmos.esa.int/h®erschel/ |
| Date Published | 2013-03-26T04:18:13Z |
| Keywords | Herschel, HSC, submillimetre, far-infrared, HIFI, PACS, SPIRE |
| Publisher And Registrant | European Space Agency |
| Credit Guidelines | European Space Agency, lis et al., 2013, 'Ammonia as a Tracer of the Earliest Stages of Star Formation', SPG v14.1.0, European Space Agency, https://doi.org/10.5270/esa-51qg935 |