Local structure and large-scale motions from young objects

Abstract

Substitution of the value 3·2 for the ratioRof total visual extinction to reddening leads to a revision of the galactic rotation curve determined by Feast and Shuttleworth. The new results agree very well with the 21-cm rotation curves, particularly with those by Kwee, Muller and Westerhout and by Shane and Bieger-Smith. The corresponding local value for Oort's constant isA= + 15.2 km sec-1kpc-1.With the exclusion of special regions like Orion, the ratioRappears to vary only little about an average of 3·2. This value gives a clearer spiral pattern than the strong variations ofRwithladvocated by Johnson; also it leads to better correlation of velocity with distance at the maxima of differential galactic rotation.