Far-Ultraviolet Spectroscopic Explorer Observations of Degree-Scale Variations in Galactic Halo OVI
Abstract
We report Far-Ultraviolet Spectroscopic Explorer (FUSE) observations of interstellar O VI absorption in the halo of the Milky Way toward 12 early-type stars in the Large Magellanic Cloud (LMC) and 11 in the Small Magellanic Cloud (SMC). The mean column densities of O VI associated with the Galactic halo toward the LMC and SMC are log<N(OVI)>=14.52+0.10-0.14 and 14.13+0.14-0.20, respectively, where the uncertainties represent the standard deviations of the individual measurements about the means. Significant variations in the O VI column densities are observed over all of the angular scales probed by our observations: 0.5d-5.0d toward the LMC and 0.05d-3.3d toward the SMC. The maximum factors by which the O VI varies between sight lines toward the LMC and SMC are ~2.8 and ~4.2, respectively. Although low-, intermediate-, and high-velocity clouds are present along most of the sight lines toward the LMC, the variations in O VI column densities are found in all of these O VI absorbing structures. The column density variations trace the structure of the hot ionized medium in the Galactic halo on scales of <<80-800 pc toward the LMC and <<6-400 pc toward the SMC (assuming that the absorption arises within the first 5 kpc above the Galactic plane).
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2002
- DOI:
- 10.1086/340231
- Bibcode:
- 2002ApJ...572..264H
- Keywords:
-
- ISM: Atoms;
- ISM: Structure;
- Ultraviolet: ISM