The Composition of the Interstellar Medium towards the Lockman Hole. HI, UV and X-ray observations

Abstract

The Lockman Hole is well known as the region with the lowest neutral atomic hydrogen colum density on the entire sky. We present an analysis of the soft X-ray background radiation towards the Lockman Hole using ROSAT all-sky survey data. This data is correlated with the Leiden/Dwingeloo survey (Galactic HI 21cm-line emission) in order to model the soft X-ray background by using radiative transfer calculations for four ROSAT energy bands simultaneously. It turns out, that an important gas fraction, ranging between 20-50%,of the X-ray absorbing material is not entirely traced by the HI but is in the form of ionized hydrogen. Far-ultraviolet absorption line measurements by FUSE are consistent with this finding and support an ionized hydrogen component towards the Lockman Hole.

arXiv comment11 pages, 11 figures, Accepted for Publication in Astronomy & Astrophysics, For full resolution images, see http://www.astro.uni-bonn.de/~mkappes/pub/ms3506.pdf

References in corpus (8)

• XMM-Newton observation of the Lockman Hole; I. The X-ray Data
• Distances and Metallicities of High- and Intermediate-Velocity Clouds
• New Results from the X-ray and Optical Survey of the Chandra Deep Field South: The 300ks Exposure
• Photospheric Abundances: Problems, Updates, Implications
• The Diversity of High- and Intermediate-Velocity Clouds: Complex C versus IV Arch
• The FUSE Spectrum of PG0804+761: A Study of Atomic and MolecularGas in the Lower Galactic Halo and Beyond
• A FUSE Survey of Molecular Hydrogen in Intermediate-Velocity Clouds in the Milky Way Halo
• Interstellar H-Alpha Line Profiles toward HD 93521 and the Lockman Window

Cited by in corpus (5)

• The Effelsberg-Bonn HI Survey (EBHIS)
• OVII and OVIII line emission in the diffuse soft X-ray background: heliospheric and galactic contributions
• An Optical Catalog of the Chandra Large Area Synoptic X-ray Survey Sources
• A Low Metallicity Molecular Cloud In The Lower Galactic Halo
• Peering Through the Muck: Notes on the Influence of the Galactic Interstellar Medium on Extragalactic Observations