C II line formation in ISM (trac #239)

[cloudy-bot]

reported by: @CloudyLex

Goldsmith.P12Collisional-Excitation-of-the-CII-Fine-Structure
Collisional Excitation of the [CII] Fine Structure Transition in Interstellar Clouds (article)
Author
{Goldsmith}, P.~F. and {Langer}, W.~D. and {Pineda}, J.~L. and {Velusamy}, T.
Journal
ArXiv e-prints
Year
2012
Month
September
Keywords
Astrophysics - Galaxy Astrophysics
Abstract
We analyze the collisional excitation of the 158 micron (1900.5 
GHz) fine structure transition of ionized carbon (C+) in terms of 
line intensities produced by simple cloud models. The single C+ 
fine structure transition is a very important coolant of the atomic 
interstellar medium and of photon dominated regions in which carbon
 is partially or completely in ionized form. The [CII] line is 
widely used as a tracer of star formation in the Milky Way and 
other galaxies. Excitation of the [CII] fine structure transition 
can be via collisions with hydrogen molecules, atoms, and 
electrons. Velocity-resolved observations of [CII] have become 
possible with the HIFI instrument on Herschel and the GREAT 
instrument on SOFIA. Analysis of these observations is complicated 
by the fact that it is difficult to determine the optical depth of 
the [CII] line due to the relative weakness and blending of the 
components of the analogous transition of 13C$+. We discuss the 
excitation and radiative transition of the [CII] line, deriving 
analytic results for several limiting cases and carry out numerical 
solutions using a large velocity gradient model for a more 
inclusive analysis. We show that for antenna temperatures up to 1/3 
of the brightness temperature of the gas kinetic temperature, the 
antenna temperature is linearly proportional to the column density 
of C+ irrespective of the optical depth of the transition, which 
can be referred to as the effectively optically thin (EOT) 
approximation. We review the critical densities for excitation of 
the [CII] line by various collision partners. We briefly analyze C+
 absorption and conclude with a discussion of C+ cooling and how 
the considerations for line intensities affect the behavior of this 
important coolant of the ISM.

Adsnote
Provided by the SAO/NASA Astrophysics Data System
Adsurl
http://adsabs.harvard.edu/abs/2012arXiv1209.4536G
Archiveprefix
arXiv
Date-Added
2012-09-21 18:09:47 +0000
Date-Modified
2012-09-21 18:09:47 +0000
Eprint
1209.4536
Primaryclass
astro-ph.GA
Local Files
~/Dropbox/bibliography/Goldsmith.P12Collisional-Excitation-of-the-CII-Fine-Structure.pdf
Remote URLs

Migrated from https://www.nublado.org/ticket/239

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    "status": "new",
    "changetime": "2019-02-04T13:07:06Z",
    "_ts": "1549285626580696",
    "description": "{{{\nGoldsmith.P12Collisional-Excitation-of-the-CII-Fine-Structure\nCollisional Excitation of the [CII] Fine Structure Transition in Interstellar Clouds (article)\nAuthor\n{Goldsmith}, P.~F. and {Langer}, W.~D. and {Pineda}, J.~L. and {Velusamy}, T.\nJournal\nArXiv e-prints\nYear\n2012\nMonth\nSeptember\nKeywords\nAstrophysics - Galaxy Astrophysics\nAbstract\nWe analyze the collisional excitation of the 158 micron (1900.5 \nGHz) fine structure transition of ionized carbon (C+) in terms of \nline intensities produced by simple cloud models. The single C+ \nfine structure transition is a very important coolant of the atomic \ninterstellar medium and of photon dominated regions in which carbon\n is partially or completely in ionized form. The [CII] line is \nwidely used as a tracer of star formation in the Milky Way and \nother galaxies. Excitation of the [CII] fine structure transition \ncan be via collisions with hydrogen molecules, atoms, and \nelectrons. Velocity-resolved observations of [CII] have become \npossible with the HIFI instrument on Herschel and the GREAT \ninstrument on SOFIA. Analysis of these observations is complicated \nby the fact that it is difficult to determine the optical depth of \nthe [CII] line due to the relative weakness and blending of the \ncomponents of the analogous transition of 13C$+. We discuss the \nexcitation and radiative transition of the [CII] line, deriving \nanalytic results for several limiting cases and carry out numerical \nsolutions using a large velocity gradient model for a more \ninclusive analysis. We show that for antenna temperatures up to 1/3 \nof the brightness temperature of the gas kinetic temperature, the \nantenna temperature is linearly proportional to the column density \nof C+ irrespective of the optical depth of the transition, which \ncan be referred to as the effectively optically thin (EOT) \napproximation. We review the critical densities for excitation of \nthe [CII] line by various collision partners. We briefly analyze C+\n absorption and conclude with a discussion of C+ cooling and how \nthe considerations for line intensities affect the behavior of this \nimportant coolant of the ISM.\n\nAdsnote\nProvided by the SAO/NASA Astrophysics Data System\nAdsurl\nhttp://adsabs.harvard.edu/abs/2012arXiv1209.4536G\nArchiveprefix\narXiv\nDate-Added\n2012-09-21 18:09:47 +0000\nDate-Modified\n2012-09-21 18:09:47 +0000\nEprint\n1209.4536\nPrimaryclass\nastro-ph.GA\nLocal Files\n~/Dropbox/bibliography/Goldsmith.P12Collisional-Excitation-of-the-CII-Fine-Structure.pdf\nRemote URLs\n}}}",
    "reporter": "gary",
    "cc": "",
    "resolution": "",
    "time": "2012-09-21T18:12:44Z",
    "component": "atomic/molecular data base",
    "summary": "C II line formation in ISM",
    "priority": "good to do",
    "keywords": "",
    "version": "trunk",
    "milestone": "no milestone",
    "owner": "nobody",
    "type": "physics"
}

[cloudy-bot]

@CloudyLex commented:

check our treatment, compare predictions with their examples

[cloudy-bot]

@peter-van-hoof-noaccount changed milestone from "" to "no milestone"