- Conference date: 15-17 November 2004
- Location: Cambridge, Massachusetts (USA)
We review recent results from X‐ray absorption line spectroscopy of diffuse hot gas in and around the Galaxy. Absorption lines of O VII, O VIII, and/or Ne IX have been detected in the spectra of LMC X‐3 as well as three AGNs and seven Galactic low‐mass X‐ray binaries. We have implemented an analysis tool, accounting for line saturation and allowing for joint fits to multiple absorption lines. Our analysis gives no significant detection of the absorption beyond the distance of the LMC. The mean temperature and density of the X‐ray‐absorbing gas are ∼ 106.4 K and 3.6 × 10−3 cm−3, assuming a filling factor of ∼ 1 and a typical interstellar metallicity as well as a collisional ionization equilibrium. These assumptions seem to be consistent with constraints obtained from diffuse O VII emission and pulsar dispersion measure observations. The spatial distribution of the hot gas can be characterized by a hot gaseous disk with a scale height of only ∼ 1 kpc and an apparent density enhancement in the Galactic central region, consistent with the surface brightness distribution of the Galactic diffuse 3/4‐keV background. The X‐ray‐absorbing species as well as those far‐UV tracers such as O VI, N V, and C IV seem to follow a trend from high to low ionization states away from the Galactic plane. These results demonstrate the potential of X‐ray absorption spectroscopy as a powerful tool in the study of the hot interstellar medium.
- Absorption spectroscopy
- Astronomical spectroscopy
- Galactic disks
- Absorption spectra
Data & Media loading...
Article metrics loading...