Probing the Spatial Distribution of the Interstellar Dust Medium by High Angular Resolution X-ray Halos of Point Sources

Abstract

We studied the X-ray dust scattering halos around 17 bright X-ray point sources using {\it Chandra} data. We use an iterative method to resolve the halos at small scattering angles from the zeroth order data in CC-mode or the first order data in TE-mode which is not or less piled-up. Using the halo models of Weingartner $&$ Draine (2001, WD01) and Mathis, Rumpl $&$ Nordsieck (1977, MRN) to fit the halo profiles, we get the hydrogen column densities and the spatial distributions of the scattering dust grains along the line of sights (LOS) to these sources. We find that the scattering dust density very close to these sources is much higher than the normal interstellar medium. For X-ray pulsars GX 301-2 and Vela X-1 with companions of strong stellar winds, the X-ray absorption column densities are much higher than the derived scattering column densities, because of the dense media around the X-ray sources produce extremely small angle scatterings which are indistinguishable from the point sources even with \textit{Chandra}'s angular resolution. For LMC X-1, most of the scattering and absorption occur in Large Magellanic Cloud, rather than in the Milky Way. From the obtained X-rays spectra, the cold gas absorption and thus the quivalent hydrogen column is determined. We have obtained the linear correlation between $N_H$ derived from spectral fits and the one derived from the halo model WD01 and MRN (except for GX 301-2 and Vela X-1): $N_{H,WD01}=(0.720\pm 0.009)\times N_{H,abs}+(0.051\pm 0.013)$ and $N_{N,MRN}=(1.156\pm 0.016)\times N_{H,abs}+(0.062\pm 0.024)$ in the units $10^{22}$ cm${}^{-2}$. High angular resolution X-ray dust scattering halos offer an excellent potential for probing the spatial distributions of interstellar dust medium.

24 pages, 7 figures, submitted to ApJ on Jan 29, 2005, Accepted by ApJ for publication on Apr 2, 2005

References in corpus (7)

• Scattering by Interstellar Dust Grains. II. X-Rays
• Boundary layer, accretion disk and X-ray variability in luminous LMXBs
• Detection of a Fully-resolved Compton Shoulder of the Iron K-alpha Line in the Chandra X-ray Spectrum of GX 301-2
• On the optical extinction and distance of GRS 1915+105
• The X-Ray Scattering Halo Around Nova Cygni 1992: Testing a Model for Interstellar Dust
• A Chandra Spectroscopic Survey of Persistent Black Hole Candidates
• X-ray Scattering Halos from the Galactic Center: Implications for Diffuse Emission Around SgrA*

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