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Issue A&A
Volume 454, Number 2, August I 2006
APEX Special Booklet
Page(s) L71 - L74
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20065387



A&A 454, L71-L74 (2006)
DOI: 10.1051/0004-6361:20065387

Letter

C $^\mathsf{18}$O (3-2) observations of the Cometary Globule CG 12: a cold core and a C $^\mathsf{18}$O hot spot

L. K. Haikala1, M. Juvela1, J. Harju1, K. Lehtinen1, K. Mattila1 and M. Dumke2

1  Observatory, PO Box 14, University of Helsinki, Finland
    e-mail: haikala@astro.helsinki.fi
2  European Southern Observatory, Casilla 19001, Santiago, Chile

(Received 7 April 2006 / Accepted 3 June 2006)

Abstract
The feasibility of observing the $\rm {C^{18}O}$ (3-2) spectral line in cold clouds with the APEX telescope has been tested. As the line at 329.330 GHz lies in the wing of a strong atmospheric H2O absorption it can be observed only at high altitude observatories. Using the three lowest rotational levels instead of only two helps to narrow down the physical properties of dark clouds and globules. The centres of two $\rm {C^{18}O}$ maxima in the high latitude low mass star forming region CG 12 were mapped in $\rm {C^{18}O}$ (3-2) and the data were analyzed together with spectral line data from the SEST. The $T_{\rm MB}$ (3-2)/ $T_{\rm MB}$ (2-1) ratio in the northern $\rm {C^{18}O}$ maximum, CG 12-N, is 0.8, and in the southern maximum, CG 12-S, ~2. CG 12-N is modelled as a 120´´ diameter (0.4 pc) cold core with a mass of 27 $M_\odot$. A small size maximum with a narrow, 0.8  $\rm {km\,s^{-1}}$, $\rm {C^{18}O}$ (3-2) spectral line with a peak temperature of $\mbox{\hbox {$T_{\rm MB}$\space }} \sim 11$ K was detected in CG 12-S. This maximum is modelled as a 60´´-80´´ diameter (~0.2 pc) hot ( $80~{\rm K} \lesssim \mbox{$T_{\rm ex}$ } \lesssim 200$ K) ~1.6 $M_\odot$ clump. The source lies on the axis of a highly collimated bipolar molecular outflow near its driving source. This is the first detection of such a compact, warm object in a low mass star forming region.


Key words: clouds -- ISM molecules -- ISM: structure -- radio lines -- ISM: individual objects: CG 12, NGC 5367



© ESO 2006


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