ASCA Observation of an ``X-Ray Shadow'' in the Galactic Plane
Abstract
The diffuse X-ray background (DXB) emission near the Galactic plane (l,b~25.6d,0.78d) has been observed with ASCA. The observed region is toward a Galactic molecular cloud that was recently reported to cast a deep X-ray shadow in the 0.5-2.0 keV band DXB. The selection of this particular region is intended to provide a constraint on the spatial distribution of the DXB emission along the line of sight: i.e., the molecular cloud is optically thick at less than 2 keV, so the bulk of the observed soft X-rays must originate in the foreground of the cloud, which is at ~3 kpc from the Sun. In the 0.8-9.0 keV band, the observed spectrum is primarily from multiple components of thermal plasmas. We report here a detection of soft X-ray (0.5-2 keV) emission from an ~107 K thermal plasma. Comparisons with the ROSAT data suggest that this soft X-ray emission is absorbed by NH=1-3×1021 cm-2, which implies a path-length through the soft X-ray-emitting regions of <~1 kpc from the Sun.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2001
- DOI:
- 10.1086/318387
- arXiv:
- arXiv:astro-ph/0009425
- Bibcode:
- 2001ApJ...547..777P
- Keywords:
-
- Cosmology: Diffuse Radiation;
- Galaxy: Structure;
- ISM: Structure;
- X-Rays: ISM;
- Astrophysics
- E-Print:
- 24 pages including 8 figures, accepted for ApJ