February 17, 2000 CfA Colloquium

Title: The Molecular Universe

Speaker: David Neufeld

Abstract: A diverse collection of molecules has been observed in a variety of astrophysical environments, including circumnuclear accretion disks in active galaxies, interstellar gas clouds, circumstellar outflows, cometary comae, and stellar and planetary atmospheres. A careful consideration of the excitation, kinematics and chemistry of astronomical molecules provides information of general astrophysical importance that is not available by any other means. Furthermore, in many astrophysical environments, molecular processes control the cooling rate, the gas temperature and the ionization level.

Over the past four years, two satellite observatories - the Infrared Space Observatory (ISO) and the Submillimeter Wave Astronomy Satellite (SWAS) - have opened up new spectral windows on the molecular Universe. Observations with these observatories have led to the widespread detection of thermal emission from astrophysical water vapor; the discovery that molecular oxygen has a surprisingly low abundance in the interstellar medium; the first detection of interstellar hydrogen fluoride; and the discovery of interstellar regions in which the ortho-to-para ratio for molecular hydrogen is out of equilibrium. These new results will be described and their implications discussed.

References for students:

Lunch on Thursday 2/17 at 12:00 pm in A-101.