Using Chandra observations we have measured the energy-resolved
dust-scattered X-ray halo around the low-mass X-ray binary GX5-1, which shows
signs of both singly- and multiply-scattered X-rays. We compared the observed
X-ray halo at various energies to predictions from a range of dust models.
These fits used both smoothly-distributed dust as well as dust in clumped
clouds, with CO and 21 cm observations helping to determine the position of the
clouds along the line of sight. We found that the BARE-GR-B model of Zubko,
Dwek & Arendt (2004 generally led to the best results, although inadequacies in
both the overall model and the data limit our conclusions. We also found that
the composite dust models of Zubko, Dwek & Arendt (2004), especially the ``no
carbon'' models, gave uniformly poor results. Although models using cloud
positions and densities derived naively from CO and 21 cm data gave generally
poor results, plausible adjustments to the distance of the largest cloud and
the mass of a cloud in the expanding 3 kpc Arm lead to significantly improved
fits. We suggest that combining X-ray halo, CO, and 21 cm observations will be
a fruitful method to improve our understanding of both the gas and dust phases
of the interstellar medium.Comment: 10 pages, accepted by Ap
