Interstellar gas in the Gum Nebula
We have surveyed the interstellar gas in and around the Gum Nebula by optically observing 67 stars at Ca II, 42 stars at Na I, and 14 stars in the ultraviolet with the Copernicus satellite. Velocity dispersions for gas in the Gum Nebula, excluding the region of Vela remnant filaments, are not significantly larger than in the general interstellar medium. The ionization structure is predominantly that of an H II region with moderately high ionization, i.e., strong Si III and S III, in clouds with Vertical BarV/sub LSR/Vertical Bar> or approx. =10 km s/sup -1/. Furthermore, we find an increase in fine-structure excitation with increasing component LSR velocity, suggestive of ram-pressure confinement for the intermediate-velocity clouds. These denser, more highly ionized clouds appear to be concentrated toward the inner Gum Nebula, where a somewhat higher velocity dispersion is found than in the outer regions. Clouds in the Gum Nebula do not show the anomalously high ionization seen in the Vela remnant clouds. The observational data are generally consistent with a model of the Gum Nebula as an H II region ionized by OB stars and stirred up by multiple stellar winds.
- Research Organization:
- Astronomy Department, University of Washington, Seattle
- OSTI ID:
- 6918597
- Journal Information:
- Astrophys. J.; (United States), Vol. 242:3
- Country of Publication:
- United States
- Language:
- English
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GENERAL PHYSICS
COSMIC GASES
ULTRAVIOLET SPECTRA
NEBULAE
ABSORPTION SPECTRA
CALCIUM IONS
EXCITATION
FINE STRUCTURE
H2 REGIONS
IONIZATION
RADIAL VELOCITY
SODIUM
SPECTRAL DENSITY
STARS
SULFUR IONS
SUPERNOVA REMNANTS
ALKALI METALS
CHARGED PARTICLES
COSMIC RADIO SOURCES
ELEMENTS
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FLUIDS
FUNCTIONS
GASES
IONS
METALS
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640105* - Astrophysics & Cosmology- Galaxies