Dr. Shauna Sallmen
Study of Interstellar Shells in our GalaxyLast updated August, 2006
Dr. Sallmen and undergraduate students at UW-La Crosse are studying interstellar shells within our own Milky Way Galaxy.
Attention undergraduates! Information about doing research with Dr. Sallmen may be found here
IntroductionThe interstellar medium (ISM) is low-density material (mostly gas) that lies between the stars. Stars forms through the mixing of this gas. When a star dies it replenishes the gas with new elements that are heavier than the original hydrogen and helium. New stars and planetary systems form from this enriched material, so "We are made of Star Stuff", as Carl Sagan says. Stellar winds and supernovae (exploding stars) send material out into the surrounding non-uniform ISM, often blowing a bubble. The ambient gas is disturbed and forms irregular shells. Young shells are typically filled with hot (about 1 million K) X-ray emitting gas, surrounded by a shell of cooler neutral material, with an interface layer of ionized material at intermediate temperatures.
ProjectThe major goal of research supported by the National Science Foundation (RUI: Study of Interstellar Shells in our Galaxy) and Research Corporation is to increase our sample of neutral hydrogen shells that have been studied in detail, in order to enhance our understanding of the processes whereby these objects interact with the ambient ISM. An adequate sample of well-studied neutral shells is essential for testing competing models of supershell formation, as well as for understanding the processes whereby energy from supernovae and stellar winds affect the structure of the ISM as a whole. This research will imporve the number of shells identified for study, the number of shells with detailed optical narrow-band imaging, and the number of shells in which absorption-line spectroscopy has been combined with multi-wavelength emission measurements.
Dr. Sallmen's Publications: A list of publications by Dr. Sallmen may be found by searching the ADS (NASA Astrophysics Data System) database.
Last updated August, 2006