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Jet Propulsion Laboratory
The Distribution of [CII] 158um emission in the Milky Way revealed by Herschel HIFI Jorge L. Pineda GOTC+ team: William D. Langer, Paul Goldsmith, Thangasamy Velusamy, Di Li, Karen Willacy, and Harold Yorke Jet Propulsion Laboratory September 2011
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[CII] Tracks Interstellar Cloud Evolution
Diffuse, atomic gas: H, C+ Transition clouds: H->H2, C+-> C0->CO Photon Dominated Regions (PDRs) H2, C+, C0,CO,13CO, etc HI H0 C+HI + H2 [CII] traces the physical conditions of the gas in all these cloud evolution stages. [CII] is the brightest far-infrared line. CO H2 got C+? Bill Langer (JPL), MW2011, September 20, 2011
![[CII] Tracks Interstellar Cloud Evolution](http://slideplayer.com./slide/9239300/27/images/2/%5BCII%5D+Tracks+Interstellar+Cloud+Evolution.jpg "Diffuse, atomic gas: H, C+ Transition clouds: H->H2, C+-> C0->CO. Photon Dominated Regions (PDRs) H2, C+, C0,CO,13CO, etc. HI H0. C+HI + H2. [CII] traces the physical conditions of the gas in all these cloud evolution stages. [CII] is the brightest far-infrared line. CO H2. got C+ Bill Langer (JPL), MW2011, September 20,")
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COBE & BICE to Herschel HIFI
CII - strongest Galactic far-IR line COBE 7o beam & ΔV ~ 103 km/s BICE 15’ beam & ΔV ~ 175 km/s COBE - widespread distribution of CII in the Galactic plane BICE - inner Galaxy distribution. 3kpc arm Molecular Ring? PDR/HII? Local ISM Nearby arms HIFI CII far-IR dust 350o < l < 30o & |b| < 3o Herschel HIFI has the spectral (<0.5 km/s) and spatial resolution (12”) to study individual clouds. BICE and IRAS
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Galactic Observation of Terahertz C+ (GOT C+)
Galactic Plane Survey - systematic volume weighted sample of 500 l.o.s. in the disk l (0o – 360o) at b = 0o, +/- 0.5o & 1o Observations completed 11 LOS 6 LOS 7 LOS 10 LOS Galactic Central Region: CII strip maps at 360 positions in on the fly (OTF) mapping mode.
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Galactic Observation of Terahertz C+ (GOT C+)
1.0 Sampling every degree in galactic longitude in the inner galaxy Sampling every 2 degrees in galactic longitude in the outer galaxy 0.5 Galactic Latitude (b) 0.0 Galactic Longitude (l) -0.5 -1.0
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HI Data from: SGPS, VGPS, and CGPS
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HI HI+CO Data from: Mopra and CSO
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HI HI+CO CII+HI CII+HI+CO Diffuse Cold Dense Warm Dense
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200 km/s b=0.0° HI LSR Velocity HI -200 km/s -180° longitude 180°
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200 km/s b=0.0° HI LSR Velocity HI -200 km/s -180° longitude 180°
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HI+CO HI HI+CO b=0.0° -180° longitude 180° 200 km/s -200 km/s
LSR Velocity HI HI+CO -200 km/s -180° longitude 180°
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HI+CO HI HI+CO b=0.0° -180° longitude 180° 200 km/s -200 km/s
LSR Velocity HI HI+CO -200 km/s -180° longitude 180°
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HI+CO+CII HI HI+CO HI+CII CII+CO+HI b=0.0° -180° longitude 180°
200 km/s b=0.0° HI+CO+CII LSR Velocity HI HI+CO HI+CII CII+CO+HI -200 km/s -180° longitude 180°
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HI+CO+CII HI HI+CO HI+CII CII+CO+HI b=0.0° -180° longitude 180°
200 km/s b=0.0° HI+CO+CII LSR Velocity HI HI+CO HI+CII CII+CO+HI -200 km/s -180° longitude 180°
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CO
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CO CO+13CO
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High-Column Density/PDRs
CO+13CO CII CII+CO CII+CO+13CO Cold Dense Diffuse Low-Column Density High-Column Density/PDRs
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200 km/s b=0.0° CO LSR Velocity CO -200 km/s -180° longitude 180°
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200 km/s b=0.0° CO LSR Velocity CO -200 km/s -180° longitude 180°
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CO+13CO CO CO+13CO b=0.0° -180° longitude 180° 200 km/s -200 km/s
LSR Velocity CO CO+13CO -200 km/s -180° longitude 180°
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CO+13CO CO CO+13CO b=0.0° -180° longitude 180° 200 km/s -200 km/s
LSR Velocity CO CO+13CO -200 km/s -180° longitude 180°
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CO+13CO+CII CO CO+13CO CII CO+CII CO+13CO+CII b=0.0° -180° longitude
200 km/s b=0.0° CO+13CO+CII LSR Velocity CO CO+13CO CII CO+CII CO+13CO+CII -200 km/s -180° longitude 180°
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CO+13CO+CII CO CO+13CO CII CO+CII CO+13CO+CII b=0.0° -180° longitude
200 km/s b=0.0° CO+13CO+CII LSR Velocity CO CO+13CO CII CO+CII CO+13CO+CII -200 km/s -180° longitude 180°
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CO+13CO+CII CO CO+13CO CII CO+CII CO+13CO+CII CII+HI
200 km/s b=0.0° CO+13CO+CII LSR Velocity CII+HI Langer et al. 2010,2011, Bill Langer’s talk tomorrow HI+CII+CO Velusamy et al. 2010, Velusamy’s poster #31 CII+CO+13CO Pineda et al. 2010 CO CO+13CO CII CO+CII CO+13CO+CII -200 km/s -180° longitude 180°
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Application: Disentangling the WNM and CNM in the Galaxy
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Disentangling the WNM and CNM in the Galaxy
The neutral interstellar medium gas is the dominant component of the ISM in galaxies. This gas consist in two components in rough thermal pressure equilibrium (Wolfire et al. 1995): the cold neutral medium (nh ~40cm-3; T=100K; CNM) and the warm neutral medium (nh ~0.5cm-3; 8000K; WNM). HI 21cm observations are only sensitive to the total column density of the gas making it impossible to disentangle the CNM and WNM gas from just from the HI emission in the galaxy. The [CII] emission traces the diffuse neutral gas but is sensitive to density and temperature. We can use GOTC+ [CII] observations along with HI to separate the CNM and WNM components in the Galaxy.
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Disentangling the WNM and CNM in the Galaxy
The [CII] intensity is proportional to density and temperature as 𝐼CII∝ nh*exp(-91.3K/Tkin) For T = 100K , and a typical HI column density of 1021 cm-2, the GOTC+ survey is sensitive to a HI gas with nh > 50 cm-3. We use the GOT C+ survey to separate the CNM and WNM components from the HI position velocity map of the Galaxy.
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CNM Column Density WNM Column Density
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CNM Column Density WNM Column Density WNM Velocity Range CNM Velocity Range
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Disentangling the WNM and CNM in the Galaxy
LSR Velocity 200 km/s HI, WNM [CII] HI, CNM b=0.0° -200 km/s -180° longitude +180°
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Total Column density and Velocity Range vs galactic longitude: b=0.0
WNM Column Density CNM Column Density Total Velocity Range Velocity Range WNM Velocity Range CNM Velocity Range
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Total Column density and Velocity Range vs galactic longitude: b=+/-0
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Total Column density and Velocity Range vs galactic longitude : b=+/-1.0
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-180° < l < 180° longitude
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-60° < l < 60°
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-30° < l < 30°
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Disentangling the WNM and CNM in the Galaxy
20% of HI mass is in the CNM (nh ~40 cm-3; T=100K) and 80% in the WNM (nh ~0.5cm-3; T=8000K) The cold neutral medium mass increases up to about 30% in the inner galaxy. 16% of the area in the galaxy is populated by cold neutral medium clouds and 84% by warm neutral medium clouds.
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Fraction of the Column density and Velocity range in CNM and WNM : b=0.0
Column Density Fraction CNM Column Density Fraction Velocity Range WNM Velocity Range Fraction CNM Velocity Range Fraction
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Fraction of the Column density and Velocity range in CNM and WNM : b=+/-0.5
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Fraction of the Column density and Velocity range in CNM and WNM : b=+/-1.0
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