The structure of the southern Milky Way

Abstract

The skies of the Southern hemisphere contain many of the objects important in the studies of galactic structure and stellar evolution. Apart from the Magellanic Clouds, the two nearest galaxies, there is a most interesting area of the Milky Way - that near the direction of the galactic centre. The greater part of it can be observed at observatories situated in the Northern hemisphere, but the region between l11 = 290° and lII = 350° is inaccessible. There is a marked disparity between our knowledge of the Northern and Southern Milky Ways, and this is reflected particularly in our understanding of spiral structure, the optical interpretation of which depends almost entirely on Northern hemisphere observations.The main object of this thesis is to add to the knowledge of the structure of the Southern Milky Way by: (a) A study of the size and distribution of H II regions. (b) The studies of two star concentrations - a visual grouping of early-type stars, and a young cluster. In (a), a photographic survey for the detection of H II regions in the Southern Milky Way is carried out. Their distribution and apparent sizes as a function of galactic longitude are used to construct a qualitative representation of spiral structure which is compared with the current models. The aims of the investigations carried out in (b) are to study the characteristics of visual groupings of early-type stars and to aid the determination of distances of spiral arms in the Southern Milky Way.