Modeling the ISM in the Milky Way Xilouris

Modeling the ISM in the Milky Way Xilouris Manolis National Observatory of Athens with: Angelos Misiriotis University of Crete ESF Workshop (Ghent) – 14 May 2007

Milky Way NGC 891 ESF Workshop (Ghent) – 14 May 2007

Optical/NIR extinction model - 9 free parameters Method: Scattered Intensities Kylafis & Bahcall, 1987, Ap. J, 317, 637 Stellar disk Bulge Dust Stars: Dust: ESF Workshop (Ghent) – 14 May 2007

FIR/Submm emission model - 6 free parameters Emitted energy by diffuse dust Stellar disk Bulge Dust Absorbed energy + Emitted energy by HII regions Energy balance FIR/Submm emission ESF Workshop (Ghent) – 14 May 2007

( ESF Workshop (Ghent) – 14 May 2007

THE FITTING PROCEDURE UGC 2048 (I-Band) Observation Model ESF Workshop (Ghent) – 14 May 2007

3 D Radiative Transfer modeling of spiral galaxies Xilouris et al. , 1999, A&A, 344, 868 ESF Workshop (Ghent) – 14 May 2007

) ESF Workshop (Ghent) – 14 May 2007

The COBE/DIRBE maps F. O. V. = 0. 7 sq. degrees Sensitivity : ~ 0. 1 MJy sr-1 @ 1. 2 μm 1. 1 MJy sr-1 @ 140μm Mollweide projection of COBE/DIRBE maps 1. 2 μm 240 μm ESF Workshop (Ghent) – 14 May 2007

Results of the RT model COBE Observations Misiriotis et al. , 2006, A&A, 459, 113 Models ESF Workshop (Ghent) – 14 May 2007

Vertical and Radial profiles ESF Workshop (Ghent) – 14 May 2007

Best fit model parameters Parameters for the dust Parameter Value Parameters for the stars Parameter 1. 2 μm 2. 2 μm ρw(0, 0) 1. 22× 10 -27 gr cm-3 ηdisk 5. 49× 10 -38 9. 94× 10 -38 erg s-1 cm-3 Hz-1 srad-1 hw 3. 3 kpc hs 2. 50 2. 20 kpc zw 0. 09 kpc zs 0. 16 0. 12 kpc ρc(0, 0) 1. 51× 10 -25 gr cm-3 ηbulge 2. 07 × 10 -38 2. 07× 10 -35 erg s-1 cm-3 Hz-1 srad-1 hc 5. 0 kpc Re 0. 68 0. 79 kpc zc 0. 1 kpc a/b 0. 61 0. 63 Tc(0, 0) 19. 2 K h. T 48 kpc z. T 500 kpc hdust≈2 hs zdust≈0. 6 zs Mc=7. 0× 107 M Mw=2. 2× 105 M ESF Workshop (Ghent) – 14 May 2007

Modeling the SED of the Milky Way (COBE/FIRAS) ESF Workshop (Ghent) – 14 May 2007

The B-V color excess for the sample of the Galactic Classical Cepheids (Fernie et al. 1995; x-axis) compared with the color excess along the same directions as derived from the model. Milky Way in the Optical bands ESF Workshop (Ghent) – 14 May 2007

Modeling the gas (H 2 and HI) in the Milky Way Parameters for the gas Parameter MH 2=1. 3× 109 M MHI=8. 2× 109 M Mdust=7. 0× 107 M } Mgas/Mdust=135 Value ρH 2(0, 0) 4. 06 cm-3 h. H 2 2. 57 kpc z. H 2 0. 08 kpc ρHI(0, 0) 0. 32 cm-3 h. HI 18. 24 kpc z. HI 0. 52 kpc Rt 2. 75 kpc

Star formation in the Milky Way <SFR>=2. 7 M /yr <ε>=2. 8% / 0. 1 Gyr The star formation rate (SFR) and the star formation rate density (ΣSFR) as a function of radius in the MW. Points correspond to different star formation estimates taken from the literature. The SFR was calculated using the strong correlation between SFR and L 100 found in Misiriotis et al. , 2004, A&A, 417, 39. Star formation rate density as a function of gas surface density in the MW disk. M yr-1 ESF Workshop (Ghent) – 14 May 2007

CONCLUSIONS Parameters for the dust and the stellar distributions in the MW are derived by applying a 3 D Radiative Transfer model to the COBE/DIRBE maps (1. 2μm… 240 μm). The conclusions follow the general trends found for distant spiral galaxies (Xilouris et al. , 1999; Bianchi 2007). The model predicts very accurately the observed (COBE/FIRAS) Submm SED of the MW. The model predicts, on average, the optical extinction observed for a sample of Cepheids. The SFR as a function of galactocentric distance calculated by the model is in good agreement with various indicators of SFR found in the literature. An “internal” Schmidt law is found for the MW which has exactly the same characteristics as the “external” Schmidt law found for external galaxies indicating a universal gas-SFR behavior not only on large scales (for the galaxy as a whole) but also on small scales (within an individual galaxy). ESF Workshop (Ghent) – 14 May 2007