Aperture synthesis observations of galactic H II regions. IV. New observations of H II regions around l = 111 .
Abstract
New observations at 6 cm and reexamination of old 21-cm observations confirm and extend the conclusions drawn earlier from previous aperture-synthesis data. In the Cas-Cep section of the Perseus Arm a loose OB association appears to be forming; formation of stars occurs in subgroups at the outer edge of neutral clouds. The area is the site of active star formation, with high-density compact H II components in S 156, S 157, S 158, and S 159. Available information on S 156 and S 158 is consistent with a model originally applied to the Orion nebula, in which an early-type star ionizes a neutral cloud from outside; ionized gas streams away from the resulting ionization front. Both S 156 and S 158 are viewed almost edge-on. A comparison of optical and radio observations shows clumping factors of 2 to 10 for S 156, 10 to 90 for S 158 and around 2 for S 162.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- July 1977
- Bibcode:
- 1977A&A....59...27I
- Keywords:
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- H Ii Regions;
- Hydrogen Ions;
- Nebulae;
- Stellar Evolution;
- Astronomical Maps;
- Centimeter Waves;
- Radio Astronomy;
- Relief Maps;
- Tables (Data);
- Astrophysics