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Distribution of Phases of the ISM - and how to see them
1.) Definition of Phases – thermal plus non-thermal 2.) ISM Questions? 3.)Theory and Observations for answers 4.)Summary points
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Definition of Phases 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 Molecular clouds CO, low J molecules Bright SF regions [C II], [O I], [C I], H2 , high J molecules T ~ 300 K More Phases! “Dark” molecular gas - GMCs H2 but no CO [CII], IR Short lived/Transient phases (shocks, shears, turbulence) [CII], OI, H2
![Definition of Phases Diffuse ionized gas [N II], T ~ 8000 K. Warm neutral gas [C II], [O I], T ~ 8000K.](http://slideplayer.com./slide/13174067/79/images/2/Definition+of+Phases+Diffuse+ionized+gas+%5BN+II%5D%2C+T+%7E+8000+K.+Warm+neutral+gas+%5BC+II%5D%2C+%5BO+I%5D%2C+T+%7E+8000K..jpg "Cold neutral gas [C II], [O I], T ~ 100 K. Molecular clouds [C II], [O I], [C I], T ~ 100 K. Molecular clouds CO, low J molecules. Bright SF regions [C II], [O I], [C I], H2 , high J molecules T ~ 300 K. More Phases! Dark molecular gas - GMCs H2 but no CO. [CII], IR. Short lived/Transient phases (shocks, shears, turbulence) [CII], OI, H2.")
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ISM Questions? 1.)What dominates the [CII] emission?
2.)What is the ISM engine? Where is the CNM/WNM? R and z? Constrains role of SN in Pth, fV, shock processing 3.)What is the porosity of ISM for ionizing photons? 4.)Formation/destruction processes and lifetimes of GMCs? 5.)How much mass is in C+/H2 regions (with no CO)? 6.)What is the roll of turbulence in heating, density, and topology?
![ISM Questions 1.)What dominates the [CII] emission](http://slideplayer.com./slide/13174067/79/images/3/ISM+Questions+1.%29What+dominates+the+%5BCII%5D+emission.jpg "2.)What is the ISM engine Where is the CNM/WNM R and z Constrains role of SN in Pth, fV, shock processing. 3.)What is the porosity of ISM for ionizing photons 4.)Formation/destruction processes and lifetimes of GMCs 5.)How much mass is in C+/H2 regions (with no CO) 6.)What is the roll of turbulence in heating, density, and topology")
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Bennett et al 1994, COBE FIRAS 7o beam
Wright et al. 1991 Line log L [C II] 158 mm [N II] 121 mm [N II] 205 mm [C I] mm [C I] mm What produces the [CII] emission? WIM – Heiles 1994 CNM – Bennett et al. 1994 GMC – Stacey et al. 1985; Shibai et al. 1991 Cubick et al 2008 [CII]
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Bennett et al 1994, COBE FIRAS 7o beam Diffuse ionized gas
[CII] [CII] T = K Cygnus X [CII] from [NII] [NII] Inferred ne Steiman-Cameron et al. 2008
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nG = n2L T Ionization: FUV, X-ray, C.R. Heating: P.E., C.R., X-ray/EUV
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 = nT WNM stable CNM stable unstable nG = n2L T T = n = 0.35 cm-3 WNM T = n = 33 cm CNM
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C II Cooling/H (CNM) > 10 CII Cooling/H (WNM)
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.
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CNM Cloud Distribution
Estimate the CNM contribution to the [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 regions and f(R). Expected for TI: Does CNM/WNM as Pth ? Does WNM at Pth >> Pmax ? Dynamical Processes t < ttcooling WNM at Pth >> Pmax ? CNM at Pth << Pmin ? 158 mm 63 mm Kulkarni & Heiles 1987
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For CNM/WNM and Pth: CII maps, NII maps, HI maps, CO maps
Galactic: STO, SOFIA, Herschel, MOPRA 1)Compare position, velocity, line width in CII and NII - Get CII in WIM and subtract from total 2)Compare position, velocity in CII and HI maps - Get CII in HI gas 3)CO maps: MOPRA -Get CII in CNM 4)CII cooling/H -> Pth STO – heterodyne on balloon flight CII, NII mapping region -20o > l > -55o; -0.5o < b < 0.5o 1)For theory need FUV : COBE, WISE, SOFIA
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For CNM/WNM and Pth: CII maps, OI maps , NII maps, HI maps CO, H2
Extragalactic: SOFIA, Herschel, Spitzer CARMA, ALMA 1)Compare position, velocity in CII, OI, NII CO, H2 - Get CII in high n, H2 gas Kaufman et al, 2006 2)Estimate CII emission from NII maps Wolfire, Hollenbach, Neufeld, 2009 in prep Oberst et al. 2006 3)CII cooling/H -> Pth But HI is CNM + WNM ! 1)For theory need FUV : Herschel dust continuum
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For CNM/WNM and Pth: CII maps, OI maps , NII maps, HI maps CO, H2
Wolfire, Hollenbach, Neufeld 2009 For CNM/WNM and Pth: CII maps, OI maps , NII maps, HI maps CO, H2 STO beam averaged I Extragalactic: SOFIA, Herschel, Spitzer CARMA, ALMA 1)Compare position, velocity in CII, OI, NII CO, H2 - Get CII in high n, H2 gas Kaufman et al, 2006 2)Estimate CII emission from NII maps Wolfire, Hollenbach, Neufeld, 2009 in prep Oberst et al. 2006 NII 205 Oberst et al 06 RCW49 3)CII cooling/H -> Pth But HI is CNM + WNM ! Carina 1)For theory need FUV : Herschel dust continuum
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For CNM/WNM and Pth: CII maps, OI maps , NII maps, HI maps CO, H2
Wolfire, Hollenbach, Neufeld 2009 For CNM/WNM and Pth: CII maps, OI maps , NII maps, HI maps CO, H2 STO beam averaged I Extragalactic: SOFIA, Herschel, Spitzer CARMA, ALMA 1)Compare position, velocity in CII, OI, NII CO, H2 - Get CII in high n, H2 gas Kaufman et al, 2006 2)Estimate CII emission from NII maps Wolfire, Hollenbach, Neufeld, 2009 in prep Oberst et al. 2006 NII 205 Oberst et al 06 RCW49 3)CII cooling/H -> Pth But HI is CNM + WNM ! Carina 1)For theory need FUV : Herschel dust continuum
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Are There Phases in the ISM?
Vazquez-Semadeni 2009 50% of gas mass in unstable Ts ??? Really 25% of WNM in unstable Ts or 15% of total mass. In plane dominated by TI. Out of plane by dynamical processes. Numerical Simulations No or weak TI: Vazquez-Semadini et al. 2000, Gazol et al. 2001, Gazol 2005 Significant TI: Piontek and Ostriker 2005, Audit and Hennebelle 2005 Hennebelle and Audit 2007 Koyama and Ostriker 2009 Heiles & Troland 2003, ApJ, 586, 1067
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= tcool/tshock >> 1 Turb << 1 TI ~ 0.3 WNM ~ 0.1 CNM
Model resolution Size of region Heating/Cooling Type and amplitude of turbulence 11 km/s 4 km/s 9 km/s Gazol et al 05 Koyama & Ostriker 09 Vturb(L) ~ La Pth(L) = Pturb(L) = tcool/tshock >> 1 Turb << 1 TI ~ WNM ~ 0.1 CNM T n Thermal Pressure Dominates in the CNM/WNM interface and for fairly large regions in WNM!
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<Tspin> = < n > = TCNM / fCNM < k > < n >
Wolfire et al. 2003 <Tspin> 400 K 10 % < fCNM < 25 % Dickey et al. 2009
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NII maps, CO maps: Ionization sources and porosity of ISM
GMC destruction Galactic and Extragalactic: SOFIA, STO, Herschel, Spitzer, CARMA, ALMA RCW Whitney et al IRAC composite map NII: Trace absorption of ionizing photons Measure the photoionization of GMCs NGC Rand, Wood, & Benjamin 2008 Lyman alpha greyscale and Spitzer IRS slits
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Ntot - NHI - NCO = N Dark Gas
Dark Gas: H2 but no CO NH2 Ntot - NHI - NCO = N Dark Gas IRAS IR Continuum Leroy, Bolatto et al.2007 ~ 30 times more H2 SMC Grenier et al ~ 30% more H2 - Star Formation and Schmidt Law Krumholz et al H2 formation Wolfire et al Dark Gas Herschel, SOFIA: IR Continuum, CII CARMA, ALMA: CO IRAM, APEX: CF+ Neufeld et al. 2006, 2009.
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Shears, Turbulence, and Shocks
Cooling is dominated by H2 and [C II]. 0.05 pc 45’’ in width D v - 40/km/s/pc 2006, IAUS 237 Herschel: [C II] and Velocity profile Wide spread H2 emission in galaxies from PDRs? Roussel et al. 2007 Herschel, SOFIA: CII, OI PDRs or Shocks? High n, low FUV indicates shocks Total cooling output = Radiative + Mechanical input
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GMC Formation/Destruction/Lifetimes
Are GMCs short lived and transient? Hartmann et al. 2001 Or long lived stable structures? Scoville and Wilson 2004 Formation: CNM cloud map and CO map Photodissociated by OB stars? Williams and McKee 1997 Shredded by shear? Koda et al. 2009 Destruction: NII, CO maps M51 CO Map using CARMA Koda et al. 2009
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Summary - CII from STO, SOFIA, Herschel
1)Velocity resolved observations map the CNM in emission 2)Get CNM/WNM distributions to test global ISM models 3)Map the Pth in the ISM and test TI or turbulence 4)Test models of GMC formation from cold gas 5)Test models of GMC destruction (neutral outflows) - NII from STO, SOFIA, Herschel 1)Test models of GMC destruction (photoionized outflows) -CII, OI, CI, CO 1)Trace energy flow into the gas (photon or mechanical) -CII, HI, CO, IR 1)Search for dark gas components
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