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Full-Text Articles in Astrophysics and Astronomy
Supershells And Propagating Star Formation, R. Mccray, Menas Kafatos
Supershells And Propagating Star Formation, R. Mccray, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
Stellar winds and repeated supernovae from an OB association will create a cavity of coronal gas in the interstellar medium, with radius greater than 100 pc, surrounded by a dense, expanding shell of cool interstellar gas. If the association has a typical initial mass function, its supernovae explosions will inject energy into the supershell at a nearly constant rate for about 5 x 10^7 yr. The supershell loses its interior pressure and enters the snowplow phase when radiative cooling becomes important or when the shell bursts through the gas disk of a galaxy, typically after a few times 10^7 yr …
Sources Of Excitation Of The Interstellar Gas And Galactic Structure, J. J. Cowan, Menas Kafatos, W. K. Rose
Sources Of Excitation Of The Interstellar Gas And Galactic Structure, J. J. Cowan, Menas Kafatos, W. K. Rose
Mathematics, Physics, and Computer Science Faculty Articles and Research
The excitation of the interstellar gas. is discussed in the light of recent evidence from γ-ray, molecular, and 21-cm line observations. Previous studies of the excitation of the interstellar gas have not taken into account the substantial density contrast that exists between spiral arms and interarm regions. We examine the role played by the galactic distribution of three sources of excitation (supernovae, OB stars, and ultraviolet stars) in determining the physical state of the interstellar gas in arm and interarm regions.
Ionization Of Carbon And Nitrogen In The Intercloud Medium, Menas Kafatos, H. Gerola, S. Hatchett, R. Mccray
Ionization Of Carbon And Nitrogen In The Intercloud Medium, Menas Kafatos, H. Gerola, S. Hatchett, R. Mccray
Mathematics, Physics, and Computer Science Faculty Articles and Research
If the intercloud medium in the solar neighborhood was suddenly ionized less than 106 years ago, the subsequent relaxation of the gas can account for the very low observed column density of C III and N III yet still leave a significant fraction ("'0.05) of ionized hydrogen and of C I in a cold (T ≈ 20° K) intercloud medium. The OAO-C Copernicus observations in the direction of X Sco are consistent with cosmic abundances and a uniform-density medium, except for C III whose predicted column density from the C m ionization zone surrounding the star is a factor ~1Q …
Statistical Time-Dependent Model For The Interstellar Gas, H. Gerola, Menas Kafatos, R. Mccray
Statistical Time-Dependent Model For The Interstellar Gas, H. Gerola, Menas Kafatos, R. Mccray
Mathematics, Physics, and Computer Science Faculty Articles and Research
We present models for temperature and ionization structure of low, uniform-density (n ~ 0.3 cm^-3) interstellar gas in a galactic disk which is exposed to soft X-rays from supernova outbursts occurring randomly in space and time. The structure was calculated by computing the time record of temperature and ionization at a given point by Monte Carlo simulation. The calculation yields probability distribution functions for ionized fraction x, temperature T, and their various observable moments. These time-dependent models predict a bimodal temperature distribution of the gas with structure in x, T that agrees with various observations. Cold regions in the low-density …