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A progress report on the Carina spiral feature

Published online by Cambridge University Press:  14 August 2015

B. J. Bok ,
A. A. Hine  and
E. W. Miller
B. J. Bok
Affiliation:
Steward Observatory, Tucson, Ariz., U.S.A.
A. A. Hine
Affiliation:
Steward Observatory, Tucson, Ariz., U.S.A.
E. W. Miller
Affiliation:
Steward Observatory, Tucson, Ariz., U.S.A.

Abstract

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The existing data on the distribution of O and B stars, of optical and radio H II sources, of H I and of cosmic dust have been assembled for the Carina-Centaurus Section of the Milky Way, lII = 265° to 305°. The published data have been supplemented by recent photoelectric UBV data and new photographic material. Two Working Diagrams (Figures 9 and 10) of the Carina Spiral Feature have been prepared. The Feature is sharply bounded at lII = 282° and again at lII = 295° in the range of distance from 1.5 to 6 kpc from the sun. Its outer rim is observed from the sun almost tangentially to a distance of 8 kpc from the sun. The Feature is found to bend at distances greater than 9 to 10 kpc from the sun, a result shown by both radio H I and radio H II data.

Figure 9 presents our basic data for the stellar, gas and dust components of the Feature. The O and early B stars and the H II Regions are closely associated and within 6 kpc of the sun they are concentrated in the range 285° < lII < 295°. The distribution in longitude of H I is broader and spills over on both sides of the O and B and the H II peak distributions. Long period cepheids yield a concentration similar to that shown by O and B stars and H II Regions. The visual interstellar absorption between lII = 282° and 295° is represented by a value AV = 0.5 mag kpc−1, or less, applicable to distances of 4 to 5 kpc. Much higher absorption is present on the outside of the Carina Spiral Feature, 265° < lII < 280°, where total visual absorptions as great as 3.5 mags. are found at distances of the order of 2 kpc. Even heavier absorption is indicated for these longitudes at 4 kpc from the sun, thus suggesting that the heavy obscuration on the outside of the Carina Spiral Feature is a phenomenon of general structural relevance (see Figures 8 and 9). Only small values of AV are found at the inside of the Spiral Feature.

The Working Diagram (Figure 10) shows that the O and B star peak and the H II peak have a width of 800 parsecs (12°) at 4 kpc from the sun, whereas the H I width is at least 1500 parsecs at the same distance. The peak of the O and B star distribution and of the H II distribution lies at about 600 parsecs (8° at 4 kpc) within the outer edge of the spiral feature. The heaviest interstellar absorption is on the outside of the Feature.

Type
Part II/Observations of Spiral Structure in Our Galaxy
Information
Symposium - International Astronomical Union , Volume 38: The Spiral Structure of our Galaxy , 1970 , pp. 246 - 261
Copyright
Copyright © Reidel 1970 

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