Herschel/HIFI Observations of EXtraOrdinary Sources: The Orion and Sagittarius B2 Starforming Regions


HEXOS will use both Herschel/HIFI and PACS to perform full line surveys of 5 sources in the Orion and Sagittarius B2 molecular clouds. These two sources contain the best-studied examples of physical and chemical processes that are prevalent in the interstellar medium and associated with the birth of massive stars and stellar clusters. This includes exploring the physical and chemical conditions that exist in gas in close proximity to massive stars that is heating and exposed to shocks, in addition to ambient gas that is directly exposed to radiation from previous generations of star formation. Herschel offers unprecedented sensitivity and near continuous spectral coverage across the gaps imposed by the atmosphere. This will open up a largely unexplored wavelength regime to high-resolution spectroscopy. 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. An example of the results expected from this program is shown in the figure, where we show a plot of the expected emission from a variety of astrophysical sources (hot core: warm gas near a massive star; quiescent gas: very coldóT~20 Kódense material that is the reservoir for future star formation; shocked gas: gas that has been subject to a strong dynamical collision with fast-moving material). As can be seen the spectrum of these objects is distinctly different and Herschel observations will, for the first-time, directly characterize the emission from these disparate sources a high spectral resolution. These type of defining observations are simply not possible from ground-based observatories, and will be useful for future far-infrared observations in our Galaxy and beyond.

The HEXOS program will essentially provide a near complete chemical assay of these organic rich sources, including numerous species that are of direct astrobiological interest such as water and various complex organics that are pre-cursors to amino acids and DNA bases. The opening of this spectral range is also an opportunity to detect the bending transitions of polycyclic aromatic hydrocarbons, whose identity has eluded astronomers for decades. Our ultimate aim is to use these data understand the extent of chemical and physical processes associated with the birth of stars. These results will also provide the basis to explore the initial conditions for the supply to organics to young planetary systems and will directly inform on the chemical processes responsible for molecular formation.

Program Coordinator: E. Bergin

Sub-Program Coordinators and Members:

Pasadena Meeting Presentations

Last modified: 3/27/2009