Recent research activities (August 2007)
My research has continued to focus on molecular astrophysics. My JHU collaborators are associate research
scientist Paule Sonnentrucker,
and graduate student Yuan Yuan. Our motivation is that – with careful
interpretation – unique information, of general astrophysical interest, can
be obtained from observations of astrophysical molecules.
In the past year, my efforts have been focused in the following
areas
1) Using the Spitzer
Space Telescope to study warm, shocked-heated gas in the interstellar
medium. Such gas is often present where
supernova explosions or supersonic outflows from young stars impact the
surrounding gas. Spectroscopic
observations of supernova remnants and regions of active star formation –
obtained with Spitzer – reveal
mid-infrared line emissions from gaseous H2, H2O, HD, CO2,
C2H2 and a large number of atomic ions; absorption by CO2
ice is also widely observed. These
observations have allowed us to understand the physical and chemical effects of
interstellar shock waves; the deuterium abundance in dense molecular clouds;
and the thermal history of the interstellar gas.
2) Planning Guaranteed Time programs
of the Herschel Space
Observatory, an ESA cornerstone mission scheduled for launch in 2008. I am involved with the HEXOS, PRISMAS, WADI, HIFISTARS,
and WISH programs.
3) Probing the chemistry of
interstellar fluorine. Fluorine is
unique among the elements of the periodic table in undergoing an exothermic reaction
with H2, the dominant constituent of interstellar molecular
clouds. We expect the product of that
reaction, hydrogen fluoride, to be widely observable with the Herschel Space Observatory, and an important
probe of molecular clouds. Our
theoretical model for the chemistry of fluorine-bearing molecules in the
interstellar gas has recently motivated the first astronomical detection of the
fluoromethylidynium (CF+) cation, which sounds exotic but is isoelectronic
with CO.
4) Studying water vapor in
dense molecular clouds, using archival data of the Submillimeter Wave Astronomy Satellite (SWAS) and the Infrared Space Observatory
(ISO).
We are grateful for generous funding from NASA’s Long Term Space
Astrophysics (LTSA) research program, the Spitzer Science Center (SSC), and the
NASA Herschel Science Center (NHSC).