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PhD ceremony Ms. Z. Nagy: Molecular line tracers of high-mass star forming regions

When:Mo 23-09-2013 at 14:30

PhD ceremony: Ms. Z. Nagy, 14.30 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Molecular line tracers of high-mass star forming regions

Promotor(s): prof. F.F.S. van der Tak

Faculty: Mathematics and Natural Sciences

High-mass stars influence their environment in different ways including feedback via their far-UV radiation and mechanical feedback via shocks and stellar winds. The penetration of FUV photons into molecular clouds creates Photon Dominated Regions (PDRs) with different chemical layers where the mainly ionized medium changes into mainly molecular. Different chemical layers in PDRs are traced by different species observable at sub-mm and far-infrared wavelengths.

In this thesis we present results from two molecular line surveys. One of them is the James Clerk Maxwell Telescope (JCMT) Spectral Legacy Survey (SLS) toward the luminous (>107 L_Sun), massive (~106 M_Sun), and distant (11.4 kpc) star-forming region W49A. The SLS images a 2x2 arcminute field around W49A in the 330-373 GHz frequency range. The detected molecular lines reveal a complex chemistry and the importance of FUV-irradiation and shocks in the heating and chemistry of the region.

The other line survey presented in this thesis is part of the HEXOS (Herschel observations of EXtra-Ordinary Sources) key program using the Herschel Space Observatory and is toward the nearby (~420 pc) prototypical edge-on Orion Bar PDR and the dense molecular condensation Orion S. Reactive ions, such as CH+, SH+, and CO+, detected as a part of this line survey trace the warm (~500-1000 K) surface region of PDRs. Spectroscopic data from the HIFI and PACS instruments of Herschel give constraints on the chemistry and excitation of reactive ions in these regions.

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