Far-ultraviolet spectroscopic explorer observations of degree-scale variations in galactic halo OVI.
HOWK J.C., SAVAGE B.D., SEMBACH K.R. and HOOPES C.G.
Abstract (from CDS):
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°.5-5°.0 toward the LMC and 0°.05-3°.3 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).
ISM: Atoms - ISM: Structure - Ultraviolet: ISM
fig 2 : NGC 346-6 = CL* NGC 346 WB 6