FAR ULTRAVIOLET SPECTROSCOPIC EXPLORER OBSERVATIONS OF INTERSTELLAR GAS TOWARD THE LARGE MAGELLANIC CLOUD STAR Sk -67°05

摘要

We report on measurements of interstellar O Ⅵ, H_2, P Ⅱ, Si Ⅱ, Ar Ⅰ, and Fe Ⅱ absorption along the line of sight to Sk — 67°05, a BO Ia star in a diffuse H Ⅱ region in the western edge of the Large Magellanic Cloud (LMC). We find log N(O Ⅵ) = 14.40 ± 0.04 in the Milky Way component and, using the C Ⅳ column density from previous IUE observations, N(C Ⅳ)/N(O Ⅵ) = 1.00 ± 0.16, a value similar to other halo measurements made with the Far Ultraviolet Spectroscopic Explorer. In the LMC component, log N(O Ⅵ) = 13.89 ± 0.05 and N(C Ⅳ)/N(O Ⅵ) < 0.4 (3 σ), since only an upper limit on N(C Ⅳ) is available. Along this sight line, the LMC is rich in molecular hydrogen [log N(H_2) = 19.50 ± 0.08]; in the Milky Way, log N(H_2) = 14.95 ± 0.08. A two-component fit for the excitation temperature of the molecular gas in the LMC gives T_(01) = 59 ± 5 K for J = 0, 1 and T_(ex) = 800 ± 330 K for J = 3, 4, 5. For the Milky Way, T_(01) = 99_(-20)~(+30) K; no excitation temperature could be determined for the higher rotational states. The Milky Way and LMC gas-phase [Fe/P] abundances are ～0.6 and ～0.7 dex lower, respectively, than solar system abundances. These values are similar to [Fe/Zn] measurements for the Milky Way and LMC toward SN 1987A.