Ultraviolet interstellar absorption toward stars in the Small Magellanic Cloud. IV. Highly ionized gas associated with the Small Magellanic Cloud.
Abstract
High-dispersion International Ultraviolet Explorer satellite spectra of seven stars in the Small Magellanic Cloud (SMC) are examined to study the properties of interstellar C IV and Si IV absorption in the SMC. Absorption by C IV or Si IV or both is found near 160 km/s for all the stars. The velocity and the relative C IV and Si IV strengths suggest UV-photoionized nebular gas as the origin of this absorption. In addition, the stars show absorption by C IV and, sometimes, Si IV in the velocity range 100-130 km/s. This velocity is 30-60 km/s more negative than that expected for normal nebular gas, and the relative C IV and Si IV strengths indicate an ionization source other than stellar UV photoionization by normal Population I stars. Possible global origins are considered for this absorption, including a hot phase of the SMC interstellar medium and a circum-SMC distribution of highly ionized gas. The only detection of interstellar N V toward a SMC star is for HD 5980. The line is broad, possibly complex, and spans the velocity range of the nebular absorption and the 100-130 km/s absorption.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1985
- DOI:
- 10.1086/163137
- Bibcode:
- 1985ApJ...292..122F
- Keywords:
-
- Interstellar Matter;
- Ionized Gases;
- Magellanic Clouds;
- Milky Way Galaxy;
- Stellar Spectrophotometry;
- Ultraviolet Absorption;
- Galactic Structure;
- Halos;
- Iue;
- Photoionization;
- Astrophysics