Physical Conditions in the Diffuse Interstellar Medium of Nearby and Distant Galaxies
Speaker: Viacheslav Klimenko
Affiliation: University of South Carolina
Date: Wednesday, February 25th
Abstract:
I will present a study of the physical properties of the cold diffuse phase of the
interstellar medium (ISM) in the Milky Way, as well as in nearby and distant galaxies.
The ISM is multiphase, consisting of hot ionized, warm, and cold neutral components.
The cold neutral phase contains both atomic and molecular gas, spanning a wide range
of densities from diffuse to dense regions. The most abundant molecules in space are
H2, HD, and CO. The analysis of their relative abundances and the populations of their
rotational levels allows us to determine the physical conditions in the ISM, such
as gas density, gas temperature, the intensity of the ultraviolet (UV) radiation field,
and the cosmic-ray ionization rate.
This talk will illustrate the identification of molecules in absorption spectra toward
background sources and the measurement of physical conditions derived from these observations.
A comparison of measurements across different galaxies shows that physical conditions
vary significantly, which may affect other properties of galaxies, such as their star
formation efficiency, chemical enrichment, dust content, gas cooling processes.