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Strömgren H? Photometry of O and B Stars in Norma
This investigation presents a study of the Galactic structure toward theNorma section of the Milky Way. The field studied is located between325° and 335° Galactic longitude and -8° to 8° Galactic latitude. New observations in the uvby? system are combined with all uvby? data currently available to collate a sample of 130 O and B stars. A uniform procedure is applied to obtain the color excesses and stellardistances for all of the stars in the sample. The sample is magnitudelimited to about V=9.5 mag and contains the brightest stars of the openclusters NGC 6087 and Ly 6, the field 2158 of Loden, the OB associationNor OB1, and stars located in the directions of R 103 and R 105. Theintrinsically luminous stars in the field studied appear to be closer tothe Sun than it has previously been thought. At about 860 pc, themajority of the stars in the sample delineate a segment consistent withthe location of the Sagittarius-Carina arm as suggested in the four-armmodel representation of the grand design of the Milky Way. A small partof the sample defines the near edge of the Scutum-Crux arm at about 1.75kpc.
| Kinematical Structure of the Local Interstellar Medium: The Galactic Center Hemisphere
A survey of interstellar Na I D1 and D2 absorption features found in thespectra of 31 early-type stars in the first and fourth Galacticquadrants reveals a new picture of the large-scale kinematics ofinterstellar gas in the vicinity of the Sun. While absorption featuresfound in the spectra of stars in the fourth Galactic quadrant show thegas expanding from stars in the Scorpio-Centaurus OB association, starsin the first Galactic quadrant, in the range of distances covered bythis survey (74--312 pc from the Sun), show interstellar gas fallingtoward the Galactic plane with a bulk motion whose component parallel tothat plane is directed toward the Scorpio-Centaurus association. Thispicture differs completely from generally accepted models in which thenearby interstellar gas flows away from the Scorpio-Centaurusassociation toward the Galactic anticenter. Evidence for the presence ofan expanding shell-like feature that is reaching the solar system ispresented.
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