Volume 383, Number 2, FebruaryIV 2002
|Page(s)||591 - 597|
|Section||Interstellar and circumstellar matter|
|Published online||15 February 2002|
Gravitationally bound cores in a molecular cirrus cloud
Radioastronomisches Institut der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
3 I. Physikalisches Institut der Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
4 Harvard-Smithonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA
Corresponding author: A. Heithausen, firstname.lastname@example.org
Accepted: 18 December 2001
Using MAMBO at the IRAM 30 m telescope we have observed a dense core in the cirrus cloud MCLD 123.5+24.9 in the dust continuum emission at 250 GHz. The core is detected as an elongated filament with an extent of , corresponding to 0.18 pc0.03 pc at an adopted distance of 150 pc. We find a close correlation between the continuum emission and previously observed C18O (10) line emission. Using standard dust models we derive hydrogen column densities of up to 1022 cm-2. The total mass for the filament is about 0.66 . We also present observations of the HC3N (32), (43), and (109) emission lines obtained with the MPIfR 100 m and the IRAM 30 m telescopes. The distribution is very different from the dust continuum and the C18O (10) line emission. HC3N is concentrated in two distinct clumps located at the ends of the filament seen in the other tracers. Based on a LVG analysis of the HC3N transitions we derive column densities of cm-2/kms-1 and volume densities of cm-3. We find that the HC3N clumps have masses of 0.13 and 0.19 . Our data demonstrate that the cirrus cloud cores are gravitationally bound, and that they show chemical structure indicating different evolutionary stages within the cloud.
Key words: stars: formation / ISM: abundances / ISM: clouds / ISM: individual objects: MCLD 123.5+24.9 / ISM: molecules / ISM: dust
© ESO, 2002
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