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Image: SH 206, Adam Block, Mount Lemmon Sky Center, University of Arizona 2008

A Model For Narrow C+ Emission Discovered By Herschel

Marcus Hughes Williams College 2014 STSCI SASP Presentation

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(Pineda et al. 2013)

(Pineda et al. 2013)

Milky Way Schematic: R. Hurt, Courtesy NASA/JPL-Caltech

ESA

Inputs: •  Electron density •  Hydrogen density •  Star Spectral Type •  Gas kinetic temperature Outputs: •  Radius of HII and PDR •  Emission measure •  C+ intensity Assumptions: •  HII region is pure hydrogen •  Ratio of C to H •  Constant density •  Temperature regime •  Collision rate coefficients

(Wiesenfeld & Goldsmith 2014)

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HII PDR

Ioniz. Front

Dissoc. Front

C and C+

C2+ and C3+

H2 HI

CO and C+

1017 cm 0 cm 1017cm 1019 cm 1019 cm

4

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60

C+

Inte

nsity

(K k

m/s

)

Star Effective Temperature (103 K)

C+ Emission from O and B Main Sequence Stars

n = 103 cm-3

ne = 80 cm-3

Input SD and SLYC from Diaz-Miller, Franco, & Shore (1998)

<p> = 0.15 Tkinetic = 103 K

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150.6, -1.0: •  O6V type star at right velocity (Crampton & Fisher 1994)

•  Observed C+ intensity: 19.4 K km/s •  Predicted C+ intensity: 85 K km/ •  Predicted C+ Intensity with Dust: 20 K km/s

Example Regions: •  087.2, -0.5 •  109.8, +0.0 •  109.8, +2.0 •  150.6, -1.0 •  202.6, +2.0 •  207.2, -2.0 •  265.5, -2.0

Background Image: 1420 MHz Continuum

(Diaz-Miller, Franco, & Shore 1998)

Future Possibilities •  Predict emission measures

•  Compare to observed emission measures •  Compare to OH measures

•  An additional tracer of molecular gas •  Consider effects of dust more generally

•  Decreases region radius, decreases C+ intensity •  Apply model to narrower inner galaxy pointings •  Consider the variable density and temperature case

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Bibliography •  Balser, D.S., Bania, T.M., Rood, R. T., & Wilson, T.L. 1995,

ApJS, 100, 371 •  Crampton & Fisher 1974, Pub. Of the Dominion Astrophysical

Observatory, 14, 283 •  Diaz-Miller, R. I., Franco, J., & Shore, S. N. 1998, ApJ, 501,

192 •  Goldsmith, P.F., Langer, W.D., Pineda, J.L, & Velusamy, T.

2012, ApJS, 203,13 •  Langer, W.D., Velusamy, T., Pineda, J.L, Willacy, K., &

Goldsmith, P.F. 2014, A&A, 561, A122 •  Pineda, J.L, Langer, W.D., Veulsamy, T., & Goldsmith, P.F.

2013, A&A 554, A103 •  Wiesenfeld, L. & Goldsmith, P.F. 2014, ApJ, 780, 183 •  Special Thanks: Philip Engelke & Paul Goldsmith

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