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| EPoS Contribution |
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The far-IR spectrum of low-mass protostars: Analysis of First results of the DIGIT and WISH Herschel Key programs
Tim A. van Kempen Harvard-Smithsonian, Cambridge, USA | |
| The far-IR part of the spectrum is the last unexplored part of the light spectrum, and for the early phases of star formation also an essential part. Not only does the SED peak at these wavelengths (50-200 micron), but in addition, many atomic and molecular transitions that contain vital information on the structure of a protostar emit at these wavelengths. Most of them have not been observed since ISO-LWS, but Herschel will allow an unprecented view on the gas and the chemistry during the early phases of star formation. The most famous example is water, but far-IR also contains high-J CO lines, OH, and atomic oxygen and carbon. All these are major targets of the spectral capabilities of the Herschel Space Observatory with the HIFI and PACS instruments. First Herschel results have very recently been obtained for the DIGIT (Dust, Ice and Gas in Time) and WISH (Water in star-forming region with Herschel) key program on Class I low-mass protostars. The current first results indicate that the spherical envelope model, long used to model (sub)millimeter lines and probe the chemistry of early phases of protostars, is unable to account for the observed intensities of water and high-J CO. The physical structure must include i) a cavity inside the envelope. to allow the warm gas tracers to escape unperturbed and ii) a 2D temperature and density structure along the cavity walls that is photon-heated by UV photons and/or shock-heated by non-dissociate shocks and iii) most likely a disk component. I will discuss these models for the gas distribution, density and temperatures using the newest Herschel results. A quite complex chemistry is also a result of this physical structure due to the heating of the cavity walls. However, the results on atomic oxygen, OH and water allow for an in-depth analysis of the basis of all oxygen chemistry, including dissociation of water. In this talk, I will present the results of Herschel on low-mass protostars, and its implications for our understanding of protostellar structure and chemistry, both in the warm inner region and along the cavity walls, both essential components in protostellar evolution. | |
| Collaborators: Ewine van Dishoeck, Leiden, NL Neal Evans, UTexas, USA Lars Kristensen , Leiden, NL Joel Green, UTexas, USA Ted Bergin, UMich, USA Ruud Visser, Leiden, USA and the WISH and DIGIT teams |
Key publication
Suggested Session: Herschel, Chemistry, Cores and Collapse, Early Phases of Disks |