On the Kinematics of Galaxies and Associated QSO Absorption Systems

The methods available for studying galaxies directly, both individually and as a class of objects, limit astronomers to certain regions of parameter space. Since most observational techniques are rooted in the collection and analysis of photons, there is always the danger of preferentially studying those objects for which this information is more readily obtained. Such selection effects can dramatically alter the physical picture one deduces. For example, detailed studies of galaxies at optical wavelengths becomes extremely difficult for objects located at distances corresponding to z approx. 1.5-3. Furthermore, certain structures are too diffuse and/or faint to detect from their emission signatures alone, even at relatively low redshifts. For example, for material in the outer regions of the galaxy, where only small amounts of star formation are occuring, it is very difficult to detect the presence of the material from optical images alone despite the advent of ever bigger and better instruments and telescopes. Fortunately, several methods exist that allow astronomers to avoid these observational hurdles. One such method is the use of quasar (QSO) absorption line systems