Condensed matter astrophysics: A prescription for determining the species-specific composition and quantity of interstellar dust using x-rays

Journal Article · Mon Jan 05 04:00:00 EST 2009 · The Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/702/2/970· OSTI ID:973566

Lee, Julia C; Xiang, Jingen; Ravel, Bruce; Kortright, Jeffrey B; Flanagan, Kathryn

We present a newtechnique for determining the quantity and composition of dust in astrophysical environments using<6 keV X-rays.We argue that high-resolution X-ray spectra as enabled by the Chandra and XMM-Newton gratings should be considered a powerful and viable new resource for delving into a relatively unexplored regime for directlydetermining dust properties: composition, quantity, and distribution.We present initial cross section measurements of astrophysically likely iron-based dust candidates taken at the Lawrence Berkeley National Laboratory Advanced Light Source synchrotron beamline, as an illustrative tool for the formulation of our technique for determining the quantity and composition of interstellar dust with X-rays. (Cross sections for the materials presented here will be made available for astrophysical modeling in the near future.) Focused at the 700 eV Fe LIII and LII photoelectric edges, we discuss a technique for modeling dust properties in the soft X-rays using L-edge data to complement K-edge X-ray absorption fine structure analysis techniques discussed by Lee& Ravel. The paper is intended to be a techniques paper of interest and useful to both condensed matter experimentalists andastrophysicists. For the experimentalists, we offer a new prescription for normalizing relatively low signal-to-noise ratio L-edge cross section measurements. For astrophysics interests, we discuss the use of X-ray absorption spectra for determining dust composition in cold and ionized astrophysical environments and a new method for determining species-specific gas and dust ratios. Possible astrophysical applications of interest, including relevance to Sagittarius A*, are offered. Prospects for improving on this work in future X-ray missions with higher throughput and spectral resolution are also presented in the context of spectral resolution goals for gratings and calorimeters, for proposed and planned missions such as Astro-H and the International X-ray Observatory.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Advanced Light Source Division; Materials Sciences Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 973566
• Report Number(s): LBNL-2580E
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Vol. 709
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
ABSORPTION SPECTRA
ADVANCED LIGHT SOURCE
ASTROPHYSICS
CALORIMETERS
CROSS SECTIONS
DISTRIBUTION
DUSTS
FINE STRUCTURE
ISM: abundances dust
extinction ISM: molecules methods: data analysis methods: laboratory techniques: spectroscopic X-rays: ISM
RESOLUTION
SIGNAL-TO-NOISE RATIO
SIMULATION
SYNCHROTRONS
X-RAY SPECTRA