| Description |
As a GT Key Program we propose to perform full HIFI and PACS line surveys of 5 sources in the giant molecular clouds Orion and Sagittarius B2. These extraordinary star-forming regions contain the best studied examples of physical and chemical processes prevalent in the interstellar medium, includinggravitational compression, thermal and turbulent pressure support, photodissociation, gas and grain chemistry in dense and diffuse quiescent gas, and shocks. With high excitation, rich chemistry, and large molecular column theygive the highest chance for new detections in a sensitive search for new molecules. Line surveys of sources (Orion KL, Orion S, Orion Bar, Sgr B2 N+M) defined by these phenomena form the backbone of this proposed program. Herschel offers unprecedented sensitivity and relative calibration accuracy,as well as continuous spectral coverage across the gaps imposed by theatmosphere, opening up a largely unexplored wavelength regime to high resolution spectroscopy. These data will take line surveys to a new level and we will use them to comprehensively characterize the physics (density,thermal balance, kinematics, radiation field) and chemistry (chemical assay,ionization, deuterium fractionation, water ortho/para ratio) of star-forming molecular gas in a manner not previously possible. The opening of this spectral range is also an opportunity to detect the bending transitions of carbon chains and polycyclic aromatic hydrocarbons, along with the rotational transitions of complex organics. Given that these sources have the richest emission spectra seen for star-forming regions in the Galaxy, we anticipate that the proposed observations will define the sub-millimeter/far infrared region of the spectrum and that these data will form a lasting Herschel legacy. |
