Modeling the Structure of the Soft X-Ray Background

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Session 8 -- General ISM, Dust
Display presentation, Monday, 9:20-6:30, Pauley Room

[8.09] Modeling the Structure of the Soft X-Ray Background

Daniel D.Kelson (UCSC), Joel N.Bregman (Univ. of Michigan)

The Bregman, Kelson, and Ashe (1993) model of the Galactic HI topology can be used to predict structure in the soft x-ray background (SXRB) on scales observable by ROSAT. The model consists of hot ($10^6$K) and warm ($10^4$K) bubbles of gas imbedded in a cold neutral substrate. The hot bubbles are likened to superbubbles filled with a thermal plasma which contribute to the SXRB. By including an isotropic extragalactic background spectrum, Galactic stellar populations, and assumed bubble size and temperature distributions in the disk, we simulate a $10\deg \times 10\deg$ region of sky centered at $ l = 209\deg $ and $b = 0\deg$. When varying the filling factors of hot and warm gas, we find little overall change in the typical scales of the image structures. Typical structures visible in the C band maps are large lobes and shadowing structures with most of the flux originating from the local bubble. In the M and I bands, we find that $1\deg$ to $3\deg$ structures dominate the images. Prominent x-ray features correlate well with inverse features in the simulated 21 cm moderate-to-high velocity channel maps; bright x-ray knots correlate well with HI holes and dark x-ray patches correlate well with HI knots. We also find that the SXRB intensity decreases for $b \approx 0\deg $ in the I band images. The M band maps show the same feature if the hot gas filling factor is lower than roughly 50\%. Future ROSAT M and I band maps in the plane should provide a useful constraint on the hot gas volume filling factor as well as on other features of the model.

Monday program listing