J/A+A/609/A22 Interstellar dust through the Fe K-edge (Rogantini+, 2018)
Investigating the interstellar dust through the Fe K-edge.
Rogantini D., Costantini E., Zeegers S.T., de Vries C.P., Bras W.,
de Groot F., Mutschke H., Waters L.B.F.M.
<Astron. Astrophys. 609, A22 (2018)>
=2018A&A...609A..22R 2018A&A...609A..22R (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Interstellar medium ; X-ray sources
Keywords: X-rays: ISM - astrochemistry - dust, extinction - X-rays: binaries
Abstract:
The chemical and physical properties of interstellar dust in the
densest regions of the Galaxy are still not well understood. X-rays
provide a powerful probe since they can penetrate gas and dust over a
wide range of column densities (up to 1024cm-2). The interaction
(scattering and absorption) with the medium imprints spectral
signatures that reflect the individual atoms which constitute the gas,
molecule, or solid.
In this work we investigate the ability of high resolution X-ray
spectroscopy to probe the properties of cosmic grains containing iron.
Although iron is heavily depleted into interstellar dust, the nature
of the Fe-bearing grains is still largely uncertain.
In our analysis we use iron K-edge synchrotron data of minerals likely
present in the ISM dust taken at the European Synchrotron Radiation
Facility. We explore the prospects of determining the chemical
composition and the size of astrophysical dust in the Galactic centre
and in molecular clouds with future X-ray missions. The energy
resolution and the effective area of the present X-ray telescopes are
not sufficient to detect and study the Fe K-edge, even for bright
X-ray sources.
From the analysis of the extinction cross sections of our dust models
implemented in the spectral fitting program SPEX, the Fe K-edge is
promising for investigating both the chemistry and the size
distribution of the interstellar dust. We find that the chemical
composition regulates the X-ray absorption fine structures in the post
edge region, whereas the scattering feature in the pre-edge is
sensitive to the mean grain size. Finally, we note that the Fe K-edge
is insensitive to other dust properties, such as the porosity and the
geometry of the dust.
Description:
We analysed a sample of six silicates and two iron sulfides.
The two iron sulfides have different origins. The pyrrothite was
synthesised in the laboratory at Astrophysikalisches Institut und
Universitaets-Sternwarte (AIU), whereas the troilite has a meteoritic
origin.
The data presented in this paper (except metallic iron) were measured
at the European Synchrotron Radiation Facility (ESRF) in Grenoble,
France.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 71 8 List of samples in our set with their relative
chemical formulae
sample/* . 8 *Individual files for extinction, scattering and
absorption cross section
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Note on sample/*: Header included 3 rows:
- Compound name and chemical formula
- Units
- Column labels
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1 I1 --- Seq Sequential number
3- 13 A11 --- Name Name (1)
15 A1 --- n_Name Note on Name (2)
17- 43 A27 --- For Chemical formula
45- 55 A11 --- State State
57- 71 A15 --- FileName Name of the file in subdirectory sample
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Note (1): The nomenclature En(x)Fs(x-1) reveals the fraction of iron
(or magnesium) included in the compound;
'En' stands for enstatite (the magnesium end-member of the pyroxene silicate
mineral series, MgSiO3) and
'Fs' for ferrosilite (the respective iron end-member, FeSiO3)
Note (2): Origin of elements as follows:
a = origin Sri Lanka
b = synthesised in laboratories at AIU Jena and Osaka University
c = meteoritic origin
d = origin: Paul Island, Labrador
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Byte-by-byte Description of file (#): sample/*
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Bytes Format Units Label Explanations
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8- 16 F9.7 keV Energy Energy around the Fe K-edge
20- 32 E13.7 cm+2/H Ext Extinction cross section
36- 48 E13.7 cm+2/H Sca Scattering cross section
52- 64 E13.7 cm+2/H Abs Absorption cross section
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Acknowledgements:
Daniele Rogantini, d.rogantini(at)sron.nl
(End) Patricia Vannier [CDS] 12-Dec-2017