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Astron. Astrophys. 329, 249-264 (1998)

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Clump mass spectra of molecular clouds

C. Kramer 1, J. Stutzki 2, R. Röhrig 2 and U. Corneliussen 2

1 Instituto de Radioastronoma Milimétrica (IRAM), Avenida Divina Pastora 7, Núcleo Central, E-18012 Granada, Spain
2 I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln, Germany

Received 30 October 1996 / Accepted 21 July 1997


We present clump mass spectra of the seven molecular clouds L1457, MCLD [FORMULA], NGC 1499 SW, Orion B South, S140, M17 SW, and NGC 7538, which were derived by a Gaussian clump decomposition algorithm from large scale isotopomeric CO maps.

We discuss in detail the reliability of the mass spectra derived by studying their dependence on the control parameters of the decomposition algorithm.

All clump mass spectra found are consistent with a power law, [FORMULA], with [FORMULA] between 1.6 and 1.8. Due to the different resolution of the observations and the different distances of the clouds, the clump masses range from several [FORMULA] M [FORMULA] in NGC 7538 down to [FORMULA] M [FORMULA], less than the mass of Jupiter, in the nearby cloud L1457. The large dynamic range covered by the observations is reflected by the high number of clumps found in each cloud, which lie between 100 and 1300. The spectral index of the clump mass distributions thus is independent of the wide range of physical properties of the clouds studied. In particular, there are no indications of a turnover of the clump mass power law index at a characteristic clump mass such as the Jeans mass, below which the clumps become gravitationally unbound. This is particularly emphasized by the clump properties in L1457 most of which are clearly substellar and which are far from being gravitationally bound objects.

Key words: interstellar medium: clouds – structure – molecules

Present address: I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany

Send offprint requests to: C. Kramer, (kramer@ph1.uni-koeln.de)

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© European Southern Observatory (ESO) 1998

Online publication: November 24, 1997