1. 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

2. 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

3. Interstellar medium: 3-phase structure

4. 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

5. Best Targets Best Instrument The Gratings
1) LMXB GS , 4U ,
4U , 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

6. 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

7. 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

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

9. GS 1826-238: + dust ... and molecules ?
85 % FeI in dust
GS : + 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

10. Contributions to interstellar oxygen

11. Analysis extended to several sight-lines
Towards
Mrk 509

12. How is oxygen distributed ?
References:
Crab nebula → Kaastra et al. (2009)
GS → Pinto et al. (2010) I
4U → 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 %

13. Abundances confirm the metallicity gradient
GS → 6-7 kpc vs. G. center
4U → 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)

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

15. 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

16. 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 = km s-1
V2 = + 50 km s-1
V3 = 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 !!!