Carbon recombination lines near 327 MHz I. "Diffuse" C II regions in the galactic disk

Roshi, D. Anish ; Kantharia, N. G. ; Anantharamaiah, K. R. (2002) Carbon recombination lines near 327 MHz I. "Diffuse" C II regions in the galactic disk Astronomy & Astrophysics, 391 . pp. 1097-1113. ISSN 0004-6361

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In earlier papers (Roshi & Anantharamaiah 2000, 2001a), we presented extensive surveys (angular resolution - 2°× 2° and 2° 6') of radio recombination lines (RRLs) near 327 MHz in the longitude range l =332°→ 89° using the Ooty Radio Telescope. These surveys have detected carbon lines mostly between l = 358°→ 20° and in a few positions at other longitudes. This paper presents the observed carbon line parameters in the high-resolution survey and a study of the galactic distribution and angular extent of the line emission observed in the surveys. The carbon lines detected in the surveys arise in "diffuse" C II regions. The l-ν diagram and radial distribution constructed from our carbon line data shows similarity with that obtained from hydrogen recombination lines at 3 cm from H II regions indicating that the distribution of the diffuse C II regions in the inner Galaxy resembles the distribution of the star-forming regions. We estimated the [C II] 158 µm emission from diffuse C II regions and find that upto 95% of the total observed [C II] 158µ m emission can arise in diffuse C II regions if the temperature of the latter 80 K. Our high-resolution survey data shows that the carbon line emitting regions have structures on angular scale ~6'. Analysis of the dual-resolution observations toward a 2 wide field centered at l =13° .9 and toward the longitude range l = 1°.75 to 6°.75 shows the presence of narrow ( ΔV≤15 km s-1) carbon line emitting regions extending over several degrees in l and b. The physical size perpendicular to the line-of-sight of an individual diffuse C II region in these directions is >200 pc.

Item Type:Article
Source:Copyright of this article belongs to European Southern Observatory.
Keywords:Galaxy: General; ISM: General; ISM: Structure; Radio Lines: ISM; Infrared: ISM
ID Code:28006
Deposited On:15 Dec 2010 12:36
Last Modified:17 May 2016 11:12

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