Neutral hydrogen in 0B associations.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Neutral hydrogen in 0B associations. Dieter, Nannielou H. Abstract Analysis of the line profiles of the neutral hydrogen survey of the galactic plane published by Muller and Westerhout has shown many cases in which neutral hydrogen appears within OB associations. Intensity contour diagrams of regions including such associations have been constructed from the line profiles for different velocities. In Morgan's unpublished catalogue of OB associations 31 are listed which occur within the limits of the Leiden survey, and for 25 of these some measure of the radial velocity is available from optical observations. For 20 of these associations a well-defined maximum in the equal-intensity contour diagrams occurs at the velocity of the association and does not occur at other similar velocities. For the remaining six associations a maximum occurs at a particular velocity, but no identification of the gas with the association can be made without stellar radial velocity measurements. The distance of a hydrogen cloud may be estimated from the distance of the association and from its velocity and a model of galactic rotation. Comparison of the distances from the two methods shows many large discrepancies. The contour diagrams show that the maximum in the equal-intensity contours changes its longitude continuously in one direction as the velocity changes. In each of the twelve cases in which it is possible to follow the maximum through such a progression this direction is consistent with the effect of the shearing action of galactic rotation. Geophysics Research Directorate Air Force Cambridge Research Center Bedford, Mass. Publication: The Astronomical Journal Pub Date: 1959 DOI: 10.1086/107993 Bibcode: 1959AJ.....64Q.329D full text sources ADS |