Low-Dispersion Spectra in the Yellow-Red Region and Their Application in Galactic Research.
Abstract
In connection with a survey of Ha-emission objects in selected fields of the southern Milky Way, photographic plates were taken with the 3 objective prism attached to the ADH Baker-Schmidt telescope of the Boyden Station. Widened and unwidened spectra were obtained on circular Eastman Kodak 103a-E plates exposed through a yellow filter Wratten No. 15. The present investigation deals with two regions along the galactic equator; one is situated in Sagittarius from 1 = 331 to 1 = 336 , in the direction of M8 and M20. The other, in Vela from 1 = 230 to 1 = 241 , extends approximately between +2 and -4? latitude and contains the aggregate of OB stars I Vel. As a by-product of the Ha survey, about 1500 relatively cool stars have been identified; the mean limiting red magnitude is 13.5. The study indicates that the Ha-emission stars are slightly concentrated around M8 and M20 and at the edge of the region covered by the aggregate I Vel, between 1 = 233 and 1 = 234?. In both Milky Way regions the surface distribution of the M stars is uniform except in areas of heavy obscuration. The C stars, on the other hand, show a definite tendency toward clustering in the Vela section at I = 233 near the aggregate of OB stars, which suggests that a branch of a spiral arm is observed at this longitude. The notable lack of brighter C stars in the Sagittarius region seems to characterize the direction of the Sagittarius cloud and the neighboring Milky Way fields.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1957
- DOI:
- 10.1086/146347
- Bibcode:
- 1957ApJ...125..728V