Engineering topics

Eder, D. C.

Publications and source records attributed to Eder, D. C..

2 records

NASA NTRS1986

The local interstellar medium. IV - The line of sight to Upsilon Scorpii

Profile fitting of Copernicus UV absorption lines separates out four components in the line of sight to Upsilon Sco. Velocities for three of the components, including the two components associated with major H I and H II regions, are in excellent agreement with the corresponding components in the nearby line of sight to Lambda Sco. The velocity of the remaining component is between the velocities of the two remaining Lambda Sco components. Column densities of the various ionization stages of C, N, Si, S, and Ar in the major H I and H II regions are in reasonable agreement with those determined from the Lambda Sco observations, with four notable exceptions. In Upsilon Sco there is more N II and substantially less S III in the H I component and significantly less N I and Si III in the H II component.

Eder, D. C.↗

NASA NTRS1985

Ionization equilibrium in isolated H II regions

Theoretical ionization equilibrium models are combined with Copernicus ultraviolet observations to study a particular H II region absorption-line component in the spectra of Lambda Sco and Upsilon Sco. The Lambda Sco observations imply that the region is characterized by a hydrogen density of approximately 0.2/cu cm and an extent along the line of sight of approximately 16 pc. Three choices for the relative placement of Lambda Sco and Upsilon Sco are considered. Conclusions are that Lambda Sco is the primary source of ionization and that there is a separation of approximately 5 pc between the H II region and Lambda Sco. Observational data support an enhanced dielectronic recombination rate for S III. Comparison of the Upsilon Sco and Lambda Sco observations suggests that spatial variations of density may be present.

Eder, D. C.↗