Query : 2001ApJ...561..238H

2001ApJ...561..238H - Astrophys. J., 561, 238-243 (2001/November-1)

Neutral atomic carbon in intermediate-velocity clouds.


Abstract (from CDS):

Using the Heinrich-Hertz-Telescope we have detected for the first time the [C I] 3P13P0 line transition at 492 GHz of neutral atomic carbon from two intermediate-velocity clouds (IVCs): IVC 135+54-46 and the Draco Nebula. Both clouds are located at high Galactic altitudes, more than 200 pc above the Galactic plane. The width of the [C I] line is quantitatively comparable to that of the 12CO rather than to that of the 13CO line, as commonly found for Galactic plane clouds. This indicates that neutral atomic carbon within the diffuse medium at high Galactic altitudes fills a significantly larger volume in comparison to the situation in dark or denser cirrus clouds close to the Galactic plane. Moreover, our observations suggest that for IVCs cooling by the [C I] line is as important as or even more important than that by the low level CO lines. PDR models used to approximate the observed line intensity ratios indicate that the molecular gas in high-altitude IVCs is exposed to a weak interstellar radiation field while its density must be high.

Abstract Copyright:

Journal keyword(s): ISM: Abundances - ISM: Clouds - ISM: individual (IVC 135+54-46, Draco Nebula) - Radio Lines: ISM - Submillimeter

CDS comments: MCLD 123.5+24.9 = GAL 123.5+24.9

Simbad objects: 5

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Number of rows : 5
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 NAME Polaris Cirrus Cloud MoC 01 52 29.6 +87 40 31           ~ 76 0
2 LDN 1457 DNe 02 55.9 +19 35           ~ 84 1
3 HRK 135.3+54.5 Cld 11 51 39 +61 13.3           ~ 23 0
4 NAME Draco Nebula RNe 16 52 +61.0           ~ 51 0
5 HD 210121 * 22 08 11.9027578440 -03 31 52.765490316   7.84 7.68     B7II 171 0

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