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Astron. Astrophys. 364, 769-779 (2000)

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ISOPHOT Serendipity Survey observations of interstellar clouds *

I. Detection of the Coldest Cores in Chamaeleon

L.V. Tóth 1,2, S. Hotzel 1, O. Krause 1, K. Lehtinen 3, D. Lemke 1, K. Mattila 3, M. Stickel 1 and R.J. Laureijs 4

1 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
2 Loránd Eötvös University, Department of Astronomy, Pázmány Péter sétány 1/a, 1117 Budapest, Hungary
3 Helsinki University Observatory, P.O. Box 14, 00014 University of Helsinki, Finland
4 ISO Science Operations Centre, Astrophysics Division of ESA, Villafranca, P.O. Box 50727, 28080 Madrid, Spain

Received 24 May 2000 / Accepted 6 October 2000

Abstract

ISOPHOT Serendipity Survey (ISOSS) observations at 170 µm reveal cold dust clouds in the nearby star forming region Chamaeleon. The distribution of the ISOSS/IRAS based [FORMULA] colour temperature have been studied in a nearby low-mass star forming region. [FORMULA] separates the obscured and intercloud regions as seen from a comparison to optical extinction data. The interstellar medium in Chamaeleon-Musca appears to be cold with dust colour temperatures of [FORMULA] K for intercloud regions, and [FORMULA] K for obscured clouds. The cold clouds account for 3 % of the area. ISOSS found 9 very cold cores with colour temperatures as low as [FORMULA] K in an 11oee [FORMULA] 8oee sized region. All C18O cores of the Chamaeleon main clouds which were crossed by ISOSS slews were also detected. Of these 11 (73 %) are cold with [FORMULA] K, 6 (40 %) are associated with very cold cores. The very cold cores have high gas column densities, [FORMULA], and 7 out of 9 have low gas kinetic temperatures as indicated by [FORMULA] K. The physical parameters of the very cold cores agree with the results of radiative transfer calculations of a spherical model cloud heated from outside by one third of the the solar neighbourhood ISRF intensity. A check of the photometric calibration of ISOSS against ISOPHOT AOT PHT22 maps and DIRBE interpolated 170 µm values showed an agreement of [FORMULA] % and [FORMULA] %, respectively. We expect to discover in total more than 100 very cold cores in the Galaxy by ISOSS.

Key words: ISM: clouds – ISM: dust, extinction – ISM: individual objects: Chamaeleon clouds – ISM: molecules – infrared: ISM: continuum – surveys

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA. Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) are MPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena, Imperial College London.

Send offprint requests to: L.V. Tóth

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© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001
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