The Norma Field Associations

The stellar OB associations toward the Norma field of the MW are studied utilizing uvbyβ photometry. We present new observations and collate all photometric data currently available to identify possible groupings. The large sample used and the reliable luminosity calibrations available in the uvbyβ photometric system are helpful to detail the structure of the field. The stars of our sample show a large scatter in their distances and reddenings, but a major concentration at about 1 kpc is quite well defined. The characteristics of the field are extensively studied based on the photometric diagrams and spatial distribution of the sample stars. The distribution of the visual extinction in the region is also analyzed and the Galactic spiral structure between l=320^{o-340^o} is discussed.