[Previous] | [Session 97] | [Next]
S.D. Friedman, P. Sonnentrucker (JHU), E.M. Murphy (UVA)
The spatial structure of the Galactic interstellar medium (ISM) is affected by many processes including bulk turbulence, winds from massive stars, and supernovae. But it has only been in the last few years that structure on scales ~1 parsec and less have been recognized. Most studies have been done by observing spatial or temporal changes in optical and radio spectra. For example, ground-based time series observations of Na I toward \delta Ori A spanning several decades (Price, Crawford, & Barlow 2000, MNRAS 312, L43) as well as observations of Na I toward stars in globular cluster M92 (Andrews, Meyer, & Lauroesch, 2001, ApJ 552, L73) reveal structure on scales of 102 to 104 AU, respectively. Frail et al. (1991, ApJ 382, 168) inferred variation in the H I column density over tens of AU from 21 cm observations of a pulsar moving through the ISM.
We report on observations of four stars in the open cluster NGC 2264, covering 910-1187Å, using the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. These are among the first UV studies of the small scale structure of the ISM. All target stars are classified as B2V or B3V, and have similar reddening characteristics, 0.05 \leq EB-V \leq 0.08. At a cluster distance of 750 pc the star-to-star separations range from 1.4 to 3.6 pc. We discuss variations in column densities of several species along these sight lines, including H2 and Fe II.
This work is supported by NASA contract NAS5-32985 to the Johns Hopkins University.