My research activity is concentrated in two areas: the chemistry of dense
interstellar clouds; and the physics and chemistry of comets. 

Dense interstellar clouds are the most massive objects in the universe consisting of
material subject to the chemical bond. The composition and the processes determining this
composition are thus of fundamental importance to our understanding of the universe. In
addition, radiation from the molecules is our main source of information on the physical
conditions in the regions of these clouds where stars are forming -- regions which are
hidden from direct optical view by obscuring dust. Moreover, the chemical composition
affects the heating and cooling processes of the cloud. Thus there is a tight
evolutionary link between chemistry, cloud structure and evolution, and star formation. 

An important part of the question of composition is the search for and identification of
new molecules. For example, our recent studies of interstellar clouds have found one of
the few cyclic molecules in space, c-C2H4O. The relative abundance of c-C2H4O and its
structural isomer CH3CHO provides information on the relative importance of different
chemical processes in clouds. Interstellar clouds, such as those believed to be similar
to the one from which the solar system condensed, have been found to contain complex
organic molecules. This suggests that organic molecules may have been present in the
solar system even before planets formed. 

Although many of the observations of these molecules have been made on the FCRAO 14m
telescope, I am also collaborating with the molecular spectroscopy-interstellar chemistry
groups at Nobeyama Radio Observatory in Japan and the Onsala Space Observatory in Sweden.
Our group has also made use of radio telescopes in Hawaii, Arizona, and even in
Antarctica. 

My other interest is in solar system objects and centers on the physics and chemistry of
the comae of comets. The same radio techniques at millimeter and submillimeter
wavelengths used to study interstellar matter are also useful in observing comets. The
recent detection of a new cometary molecule, NS, provides insight into the chemistry of
nitrogen and sulfur in comets. Observations of HCN, HNC and other molecules can give
information on the dynamics of the coma gases, as well as on the differences in
composition among comets and the relation of comets to interstellar material. Since
comets were clearly a source of organic matter for the early Earth, studying the nature
and links between the organic chemistry in interstellar clouds and comets is an important
part of NASA's astrobiology program.

Other

PDF

Spectra of Nearby Galaxies Measured with a New Very Broadband Receiver (with Gopal Narayanan, Ronald L. Snell, Neal R. Erickson, Aeree Chung, Mark H. Heyer, and Min Yun), Astronomy Department Faculty Publication Series (2008)

Three-millimeter-wavelength spectra of a number of nearby galaxies have been obtained at the Five College...