Evidence for an X-ray Emitting Galactic Bulge: Shadows Cast by Distant Molecular Gas
Abstract
A mosaic of 7 ROSAT PSPC pointed observations in the direction of (l,b ~ 10,0 deg) reveals deep X-ray shadows in the 0.5-2.0 keV band cast by dense molecular gas. The comparison between the observed on-cloud and off-cloud X-ray fluxes indicates that ~43% of the diffuse X-ray background in this direction in both the 3/4 keV and 1.5 keV bands originates behind the molecular gas, which is located at 2-4 kpc from the Sun. Given the short mean free path of X-rays in the 3/4 keV band in the Galactic plane (~1 kpc assuming an average space density of 1 cm^-3), this large percentage of the observed flux which originates beyond the molecular gas most likely indicates a strong enhancement in the distribution of X-ray emitting gas in the Galactic center region, possibly associated with a Galactic X-ray bulge.
Keywords
Cite
@article{arxiv.astro-ph/9612039,
title = {Evidence for an X-ray Emitting Galactic Bulge: Shadows Cast by Distant Molecular Gas},
author = {Sangwook Park and John P. Finley and Steven L. Snowden and Thomas M. Dame},
journal= {arXiv preprint arXiv:astro-ph/9612039},
year = {2009}
}
Comments
16 pages LaTex, 2 figures. Accepted for the publication in Astrophysical Journal, Letters