Observational Astronomy

Over 147 molecules have now been detected in interstellar and circumstellar environments (see the Cologne Database for Molecular Spectrosocpy for the most up-to-date list). The great majority of detected interstellar molecules have been observed in hot cores, which are regions around newly-formed stars where the organic molecules have been liberated through thermal evaporation of grain surface ices. Grain surface and gas-phase chemistry in these regions leads to a wide array of complex organic molecules.

Once we characterize molecules with our laboratory THz spectroscopy, our group conducts observational searches for these species in astronomical sources. The ultimate goal is to elucidate prebioitc chemical formation and destruction pathways in interstellar environments. While there are many hot cores, previous work has focused on the Orion-KL and Sgr B2 regions. Our group is now beginning to do spectral line surveys of other hot core regions with varying physical properties so that we can study the effects of these physical conditions on hot core chemistry.

Most of our work uses ground-based radio telescopes, such as the Caltech Submillimeter Observatory (CSO) on Mauna Kea in Hawaii, the Green Bank Telescope (GBT)) in West Virginia, and the Combined Array for Research in Milimeter Astronomy (CARMA) in northern California. Upper atmosphere or space-based observatories such as the SOFIA observatory and the Herschel Space Observatory will allow more highly sensitive searches to be conducted without interference form the Earth's atmosphere. In addition, high spatial resolution and sensitivity will be possible with the upcoming Atacama Large Millimeter Array (ALMA), which is currently being constructed in Chile and will consist of 64 dishes.

Dr. Widicus Weaver's most recent observational work has been in collaboration with the Caltech Submillimeter Astrophysics Group to use prototype wideband receivers to conduct broadband, high sensitivity spectral line surveys of star forming regions using the CSO.

These surveys surpass the sensitivity of previously-published observations by an order of magitude, and have reached the spectral line confusion limit in the Orion and Sgr hot cores. The results of these surveys provide spectral line information for comparison to future laboratory spectra. Our undertsanding of astrochemical mechanisms are refined with the information gained from these observations. The physical properties of the identified molecules as well as any newly identified species can be entered into astrochemical models, placing constraints on the possible pathways for the formation of biologically-relevant species.