Doug Burke writes:
>The soft background component does vary spatially,
>so that is definitely one thing to think about (as an example see the
>discussion in http://xxx.lanl.gov/abs/astro-ph/0105093 - Merger shocks in
>galaxy clusters A665 and A2163 and their relation to radio halos by M.
>Markevitch & A. Vikhlinin ).
The background data were collected from a number of Chandra fields at high
Galactic latitudes; they should provide a good match for the quiescent
background Nh = 1-5e20. We usually find good fits with Nh fixed at a
At lower Galactic latitudes there indeed may be contaminating
components. Usually they are soft, which would bias Nh low. So I doubt that
Eric's problem is related to the background.
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