A Rich New Approach to Determining the Structure and Dynamics of the Milky Way Galaxy

Tyler J. Foster

This work will present a new method aimed toward explaining long-standing and foundational problems in Galactic astronomy that descend from the uncertain dynamics in the Galaxy's second quadrant. The overall method is based on a mathematical model of the cumulative H I column density with Galactocentric radius. This model, when confronted with the radio-wavelength H I data from the Canadian Galactic Plane Survey (CGPS), is successful in reproducing the large-scale distribution of H I in the Galactic disk. The method's cardinal technique is the fitting of the model to the observational data. This step provides three fundamental outputs for a given direction: the predicted run of neutral hydrogen column density with distance, the relationship between velocity and distance (the velocity field), and parameters that describe the smooth large-scale structure of the Milky Way's thin H I disk. This thesis begins by fully developing and describing the method. The method's accuracy as a distance indicator for individual astronomical objects is tested, and new distances are derived for 30 H I regions in the Galactic plane across the second quadrant, in the range 90o <= l <= 140o. The method's importance to studies of astronomical objects is demonstrated in the second part (Chapters 3 and 4), where new reddenings and distances to a collection of objects near l = 93o are calculated, and are shown to be nearly one-half of those predicted from Galactic kinematics. The astrophysical characteristics of the supernova remnant 3C434.1 and its surrounding H I shell that descend from a proper distance calculation are presented. The fifth chapter exhibits the method's ability to predict the velocity field in a given direction. Selected velocity fields from across the CGPS Phase I (90o <= l <= 140o) are derived. General characteristics of the H I velocity fields are consistent with a falling rotation curve combined with the effects of a spiral arm potential ascribed to the Perseus Arm. The magnitude of the field's deviation from flat circular rotation is observed to have a strong latitude dependence, and probably arises due to non-axisymmetric motions induced by the Perseus Spiral Arm. The thesis concludes with a look at future research directions.