Chemical and physical structure of the Interstellar medium through X-ray Spectroscopy Ciro Pinto(1) J. S. Kaastra(1,2), E. Costantini(1), F. Verbunt(1,2) (1) SRON – Netherlands Institute for Space Research (2) Astronomical Institute, Utrecht University

Interstellar medium (ISM) and Galactic life cycle Crucial role in the evolution of the entire Galaxy Stellar evolution Heavy elements ISM Metallicity gradient towards the G. center Evolution of the Galaxy

Interstellar medium: 3-phase structure

X-ray Spectroscopy: a powerful tool Abundances + Constituents Absorption edges and lines Column densities Recent results: Composition similar to the Sun Ne/O ratio higher than Solar value Metals depleted into dust grains Ionized gas ~ 10% of total NH Galactic Ionized Gas

Best Targets Best Instrument The Gratings 1) LMXB GS 1826-238, 4U 1820-303, 4U 1636-536, GX 339-4, 2) Other: Crab, V2491 Cyg, Mrk 509 Best Targets Best Instrument Towards The Gratings on board: XMM-Newton + Chandra Ne, O, Mg & Fe edges

GS 1826-238: neutral gas Absorption: Cold neutral gas → Ne, O, Mg & Fe Fitting package SPEX (Kaastra et al. 1996) Absorption: Cold neutral gas → Ne, O, Mg & Fe Continuum: (Thompson 2008) Residuals: 17.5 Å → dust 22.9 Å → dust 21.6 Å → O VII 23.3 Å → O II

GS 1826-238: + ionized gas COLD GAS → O I + O II Model 2: 3-phase Gas WARM GAS → O III + O IV HOT GAS → O VII + O VIII Model 2: 3-phase Gas Cold, warm and hot phases Abundances same for all phases Oxygen Edge

GS 1826-238: + dust ... and molecules ? Iron Edge GS 1826-238: + dust ... and molecules ? Pure-gas is not satisfactory ! → need gas + dust !!! Current models in SPEX: - Shielding by dust grains - Structure by molecules Oxygen Edge

GS 1826-238: + dust ... and molecules ? 85 % FeI in dust GS 1826-238: + dust ... and molecules ? Fe: Metallic, Fe2SiO4, Fe2O3 ? O: CO, H20 ice, MgSiO3 .. ? Mix: Pyroxene, Fayalite, .. Models in development !!! 15 % OI in dust 80-90 % of iron in dust 10-20 % oxygen in dust

Contributions to interstellar oxygen

Analysis extended to several sight-lines Towards Mrk 509

How is oxygen distributed ? References: Crab nebula → Kaastra et al. (2009) GS 1826-238 → Pinto et al. (2010) I 4U 1820-303 → Costantini et al. (in prep) All the sources → Pinto et al. II (in prep) How is oxygen distributed ? Ionized gas provides < 10 % of O-column Dust silicates provide ~ 10 – 15 %

Abundances confirm the metallicity gradient GS 1826-238 → 6-7 kpc vs. G. center 4U 1820-303 → 7-8 kpc vs. G. center All elements are over-abundant with respect to Solar composition Over-abundances almost agree Metallicity gradient (measured with stars)

Abundances confirm the metallicity gradient Towards Mrk 509 References: Crab nebula → Kaastra et al. (2009) GS 1826-238 → Pinto et al. (2010) I 4U 1820-303 → Costantini et al. in prep All sources → Pinto et al. II in prep Abundances increase (differently) towards the Galactic Center Typical error bar

Conclusion and future Chemical analysis: abundances Structural analysis: phases & ratios Evolutionary effects: metallicity gradient Future: ASTRO-H, IXO, Lab. Data + UV data ! → distinguish better the compounds → mapping ISM → investigate the evolution of our Galaxy

Wonderful COS/HST UV data of Mrk 509 big Campaign Mrk 509 COS/HST data (J. Kriss group at STSCI) Wonderful COS/HST UV data of Mrk 509 big Campaign 3 ISM warm gas with different velocities V1 = - 7 km s-1 V2 = + 50 km s-1 V3 = - 310 km s-1 Si1 IV = 17.6 m-2 Si2 IV = 17.5 m-2 Si3 IV = 17.2 m-2 Si IV Si IV Configuration Si IV 2p63s-2p63p Preliminary !!!