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The X-ray side of the absorption by interstellar dust

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.) .

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The X-ray side of the absorption by interstellar dust

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  1. The X-ray side of the absorptionby 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. 18-22 2013, 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 (0.7-7.1keV), 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-raybinariesareusedasbackgroundlight mapping all thegalacticplane • Both scattering and absorption can be simultaneously studied

  4. 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=400-1000), 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 + 2013) NH=1-4x1021cm-2

  9. FeS Are we detecting GEMS? 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. Electron Microscope Utrecht (EMU) 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 Measurements: PHOENIX (test) DUBBLE Fe K edge at 7.1 keV

  13. NH=3x1022cm-2 Si K edge measurements (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. 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. Conclusions

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