1. The X-ray side of the absorption by interstellar dust
Elisa Costantini (SRON)
C. De Vries, S. Zeegers (SRON), C. Pinto (IoA), H. Mutschke (Jena U.), F. de Groot (Utrecht U.) , R. Waters (SRON), A. Tielens (Leiden U.)
The life cycle of dust in the Universe, Nov , Taipei

2. Why X-rays?
The X-ray band offers complementary information with respect to longer wavelengths. This opens up a new science window for ID investigation.

3. Uniqueness of X-rays Gas phase: N, O, Fe, Ne, Mg, Si
Dust: O (0.54keV), Fe ( keV), Mg (1.3keV), Si(1.87keV) all constituents of silicates!
Dust: prominent iron features (Fe L and K-edge),
Element depletion is straightforward to determine
Sensitive to a large range of column densities.
X-ray binaries are used as background light  mapping all the galactic plane
Both scattering and absorption can be simultaneously studied

4. Scattering produces a halo of diffuse emission around the source.
Galactic Center observed by ROSAT
0.1-2 keV
Scattering produces a halo of diffuse emission around the source.
The intensity/shape of the halo depends on energy, dust size distribution, dust spatial distribution (Overbeck 71; Mauche & Gorenstein 91; Predehl & Schmitt 95 Predehl & Klose 96; Costantini+05; Smith, Dame, Costantini+06)
Absorption is seen in spectra of X-ray sources behind dust.
Dust distorts the photoelectric edges depending on
the dust chemical composition
(Lee+2005, 2009; Pinto, Kaastra, Costantini+2010,2013; Costantini+2005, 2012)

5. Absorption
The light of the background source is absorbed by the intervening dust and gas 
dozens of neutral and ionized absorption features. X-rays have lower resolution (R= ), but many more transitions than UV  better determination of multi-temperature components

6. Dust spectral effects
(Lee+09)
As NH increases we are sampling denser and denser
environments up to the Galactic Center region.
Most edges are modified by measurable dust absorption (shift +smearing)
Depending on the dust environments we can access different edges

7. Absorption by diffuse ISM
optimal view of O and Fe (NH~2x1021cm-2)
 Fe is 90% and O 20% in dust
Mg-rich silicates (rather than Fe-rich)
 Metallic iron + traces of oxides
(Costantini+12 )

8. Mapping the diffuse ISM
Analysis of the diffuse gas in different directions
Metallic iron is favorite over e.g. Olivine.
Depletion:
15-25% for O
65-90% for Fe
(Pinto, Kaastra, Costantini )
NH=1-4x1021cm-2

9. Are we detecting GEMS?
FeS
Results from X-rays, using different instruments and techniques : evidence of Mg2SiO3 + Fe + oxides Is there any compound with such composition? GEMS= glass with embedded metal and sulfides (e.g. Bradley+04) They have an interplanetary origin, but some of them may have ISM origin (e.g. Keller&Messenger 08, Ishii+08)
Metallic iron
Mg silicate

10. Shortcoming:
relatively few (and sparse) lab X-ray measurements of compounds interesting for astronomy are available for comparison with the data
 Possible bias in the results

11. The DUSTLAB project
Collect relevant dust samples of astronomical interest: e.g. silicates, sulfates
11 samples (courtesy of H. Mutschke)
Crystalline & amorphous silicates
Measurements of all relevant edges (O, Fe, Mg, Si, S)
comprehensive modeling of observed edges
Simultaneous fitting, reduced degeneracy
Implemetation into fitting X-ray codes
addition to existing measurements
dust+gas+source modeling
Complementary data: X-ray scattering halos, Spitzer (10µm feature), HST (oxygen depletion), CO maps

12. Measurements: Electron Microscope Utrecht (EMU) LUCIA O K at 0.543 keV
Fe L at 0,.7 keV
LUCIA
Mg K at 1.3 keV
Si K at 1.84 keV
PHOENIX (test)
DUBBLE
Fe K edge at 7.1 keV

13. Si K edge measurements CHECK Poster by S. ZEEGERS! NH=3x1022cm-2
(Zeegers, Costantini+ in prep)
Tested on the Si K edge of GX5-1, in the Galactic Center region:
Depletion: 0.74
Abundance :1.5
Dust: amorphous pyroxene!
Soleil-Paris LUCIA beamline: Mg and Si edges
Measurable differences among silicates. 1
CHECK Poster by S. ZEEGERS!

14. The X-ray future of dust
1999
1999
XMM-Newton
CHANDRA
Astro-H
Athena+ XIFU
2015
Astro-H SXS
Athena+….2028?
Dense environements can be investigated!

15. Future missions: Athena+
Investigation of dense environments NH=1x1023cm-2
SiK and FeK edges
Galactic center densest regions (dust composition, depletion) will be only accessed with Athena+

16. Conclusions X-rays are a powerful tool to study interstellar dust
Current and future instrumentations + new lab measurements will help in solving the still open (and important) issues about dust.

17. Preliminary results Fe K edge Amorphous and Crystals show DUBBLE
Measurable differences
DUBBLE
O K EMU
Striking differences do not show up in every edge
 Need for multiple edge fitting