The distribution and kinematics of interstellar O VI in the milky way

Abstract

We present the results of a survey of interstellar O VI absorption in the Milky Way (MW) towards 69 stars in the Large Magellanic Cloud obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). The integrated MW O VI column densities log N(O VI) are in the range from 13.68 to 14.73 with a mean of 14.26+0.07−0.09 atoms cm−2. The O VI exponential scale height is found to be 2.28 ± 1.06 kpc. The O VI column density correlates with the Doppler parameter b. The O VI velocity dispersion ranges from 14.0 to 91.6 with an average value of 62.7 km s−1. These high values of the velocity dispersion reveal the effect of turbulence, multiple velocity components and collision on broad O VI profiles. There is a significant variation of the O VI column density on all scales studied (0.◦0025–6.◦35). The smallest scale for which O VI column density variations has been found is Δθ ∼ 9 arcsec. A comparison of the O VI velocity profiles with Fe II indicates the presence of intermediate-velocity cloud and/or high-velocity cloud components in the O VI absorption