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Infrared Cooling Lines of the ISM

Infrared Cooling Lines of the ISM. 1.) Galactic [C II] 158 m m emission - [N II], [C I]. 2.) Component Emission Diffuse ionized gas [N II], T ~ 8000 K Warm neutral gas [C II], [O I], T ~ 8000K Cold neutral gas [C II], [O I], T ~ 100 K

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Infrared Cooling Lines of the ISM

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  1. Infrared Cooling Lines of the ISM 1.) Galactic [C II] 158 mm emission - [N II], [C I] 2.) Component Emission Diffuse ionized gas [N II], T ~ 8000 K Warm neutral gas [C II], [O I], T ~ 8000K Cold neutral gas [C II], [O I], T ~ 100 K Molecular clouds [C II], [O I], [C I], T ~ 100 K Bright SF regions [C II], [O I], [C I], H2 , T ~ 300 K 3.)Turbulence structure and heating [C II], H2, [O I] 4.)Summary of Line Intensities and Future Directions

  2. ISM Questions? 1.)What dominates the [CII] emission? 2.)Where is the CNM/WNM? R and z? Constrains role of SN in Pth, fV, shock processing Constrains MHD simulations of Galactic disk 3.)How much mass is in C+/H2 regions (with no CO)? 4.)What is the heating rate in diffuse gas and PDRs? 5.)What is the molecular cloud structure – penetration of UV 6.)What is the roll of turbulence in heating, density, and topology.

  3. Bennett et al 1994, COBE FIRAS 7o beam Wright et al. 1991 Line log L [C II] 158 mm 7.7 [N II] 121 mm 6.9 [N II] 205 mm 6.7 [C I] 370 mm 5.5 [C I] 610 mm 5.3 What produces the [CII] emission? WIM – Heiles 1994 CNM – Bennett et al. 1994 GMC – Stacey et al. 1985; Shibai et al. 1991 [CII]

  4. Bennett et al 1994, COBE FIRAS 7o beam Diffuse ionized gas [CII] SOFIA gets ne Pth in resolved H II regions Petuchowski & Bennett 1993 Observed Ratio Predicted Inferred ne

  5. Bennett et al 1994, COBE FIRAS 7o beam Diffuse ionized gas [CII] [CII] [CII] from [NII] Cygnus X Petuchowski & Bennett 1993 Observed Ratio [NII] Inferred ne Steiman-Cameron et al. 2008

  6. Wolfire, McKee, Hollenbach, & Tielens (2003) Ionization: FUV, X-ray, C.R. Heating: P.E., C.R., X-ray/EUV Cooling: [CII], [OI], Lya, e- recombination WNM stable = nT CNM stable unstable nG = n2L T T = 7860 n = 0.35 cm-3 WNM T = 85 n = 33 cm-3 CNM

  7. Wolfire, McKee, Hollenbach, & Tielens (2003) = nT Pmax Pmin Grain photoelectric 158 mm C II Cooling/H (CNM) > 10 CII Cooling/H (WNM) 63 mm C II emission isolates the CNM clouds! Previously seen only in absorption.

  8. CNM Cloud Distribution Estimate the CNM contribution to Galactic [C II] emission. With H I get CNM/WNM mass distribution. If SNR dominate the topology then MCNM > MWNM If SNR are small MCNM < MWNM With HI get the thermal pressure in clouds. Compare Pth in arm and interarm Does Pth drive gas into cold phases through thermal instability? Grain photoelectric 158 mm 63 mm Kulkarni & Heiles 1987

  9. CNM Cloud Distribution CNM height above Galactic plane tests hydrodynamic models Grain photoelectric 158 mm 63 mm Piontek & Ostriker 2007

  10. e Heating: Photoelectric Cooling: C+ 158 mm O 63 mm Diagnostics: C+ 158 mm O 63 mm, 145 mm Si+ 35 mm, Fe+ 26 mm Dust Continuum PAH 3.3, 6.2, 7.7, 8.6 11.2 mm

  11. Dark Gas Heating: Photoelectric Cooling: C+ 158 mm C 609 mm Diagnostics: C+ 158 mm C 609 mm, 370 mm H2 vibration-rotation UV: H2 v=6-4 Q(1) 1.6 mm Coll: H2 0-0 S(2) 12.3 mm PAH

  12. Dark Gas Heating: Photoelectric Cooling: CO Diagnostics: CO

  13. Dark Gas Diffuse Cloud SOFIA Observes all the dominant coolants! Dark Gas: Column density, [CII] ~ FUV, n FUV,eff ~ 30 x ISRF Need Map of GMC Is [CII] high? Evenly distributed? One or two bright spots? Wolfire, Hollenbach, & McKee 2008

  14. Tielens et al. 1993 Orion Bar PAHs Allers et al. 2005 TEXES Observations H2 S(1), S(2), S(4) 2’’ and 4 km/s CO H2 1-0 H2 0-0 and upper J CO lines are too hot! 400 - 1000 K H2 0-0 has low critical densities High spatial resolution to isolate temp regions High spectral resolution to distinguish shocks/thermal Heating rate x 3 in atomic gas Heating rate 1/2 in molecular gas Reduced UV extinction by 3 Increased CR ionization by 20

  15. More PDR Tests! [O I] 63 mm absorption profile [O I] 145 mm line plus [C II] + [O I] 63 mm provides diagnostics [C II] penetration into molecular cloud provides cloud topology M 17 SW [C II] M 17 Spitzer IRAC 1988 10 arcmin

  16. Turbulent Dissipation in Shear Layers 0.05 pc 45’’ in width D v - 40/km/s/pc 2006, IAUS 237 Cooling is dominated by H2 and [C II]. Additional tests of turbulence: [CII]/FIR dispersion in clouds Juvela, Padoan, Jimenez 2003 [O I] 63 mm emission components?

  17. SOFIA Spectral Resolution (km/s) vs. Wavelength GREAT ISM Cooling Lines N II 205 mm CASIMIR C II 158 mm H2 S(6) EXES OI 63 mm Km/s FIFI-LS SAFIRE FLITECAM FORCAST HAWC HIPO Wavelength (µm)

  18. CNM Clouds Size at 10 kpc [C II] [O I] RG=8.5 kpc RG=8.5 kpc 3 pc 1 – 2 arcmin 4x10-10 W/m2/sr 4x10-11 W/m2/sr 3x10-18 W/m2 (17’’) 4x10-20 W/m2 (7’’) dv 3 km/s RG=3 kpc RG= 3 kpc 2x10-9 W/m2/sr 3x10-10 W/m2/sr 1x10-17 W/m2 (17’’) 3x10-19 W/m2 (7’’) Wolfire et al. 2003 GREAT Sensitivity In plane and out of plane [CII] observations possible ? in thin slice. Spectral resolution 1 km/s. STO, Herschel also possible O I in diffuse gas not possible unless there are shock components [CII]

  19. Molecular Clouds - Dark Gas Size at 10 kpc [C II] [O I] <FUV> 35 x ISRF <FUV> 35 x ISRF 30 pc 10 – 20 arcmin 1x10-7 W/m2/sr 4x10-8 W/m2/sr 3x10-16 W/m2 (17’’) 4x10-17 W/m2 (7’’) dv 5 km/s Wolfire et al. 2008 [C II] GREAT Sensitivity [O I] Map [CII] and [OI] from GMC Spectral resolution 1-2 km/s. Needs fast mapping.

  20. Molecular Clouds - Bright PDRs Size [C II] [O I] H2 0-0S(1) FUV = 103 x ISRF FUV = 103 x ISRF FUV = 103 x ISRF 5 pc 20 – 30 arcmin 5x10-7 W/m2/sr 3x10-6 W/m2/sr 1x10-7 W/m2/sr 2x10-15 W/m2 (17’’) 1x10-14 W/m2 (7’’) 2x10-17 W/m2 dv 5 km/s Kaufman et al. 2006 – face on Need spatial and spectral resolution EXES GREAT H2 0-0S(1)

  21. Turbulence - Shear Size [C II] H2 0-0S(0) 0.05 pc 15’’ arcsec 9x10-9 W/m2/sr 4x10-9 W/m2/sr 5x10-17 W/m2 (17’’) 1x10-18 W/m2 (4’’) dv 2-3 km/s Falgarone et al. 2007 Turbulence – Structure[CII]/FIR in CNM Turbulence – Shocks [OI] ? EXES GREAT [CII] H2 0-0S(0)

  22. The End!

  23. Grenier et al. 2005, Science, 307, 1292 IRAS Ntot - NHI - NCO = N Dark Gas IRAS 100 mm Dark Gas: Not HI Not CO Ntot - NHI - NCO = N Dark Gas EGRET g rays

  24. Heiles & Troland 2003, ApJ, 586, 1067

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