Extending the limits of globule detection ISOPHOT serendipity survey observations of interstellar clouds II

L. V. Tóth, Cs Kiss, M. Juvela, M. Stickel, U. Lisenfeld, S. Hotzel

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Small isolated clouds were discovered by the ISOPHOT 170 μm Serendipity Survey (ISOSS) as faint I170 < 13 MJy sr-1 FIR sources. One of them is ISOSS J20246+6540, a cold (Td ≈ 14.5 K) pointlike ISOSS source without an IRAS pointsource counterpart. In the Digitized Sky Survey B band it is seen as a 3 inches size bipolar nebulosity with an average excess DSS blue band surface brightness of 8% of the background's photographical density. The CO column density distribution determined by multi-isotopic, multi-level CO measurements with the IRAM-30 m telescope agrees well with the optical appearance. An average hydrogen column density of ≈ 1021 cm-2 was derived from both the FIR and CO data. Using a kinematic distance estimate of 400 pc the NLTE modelling of the CO, HCO+, and CS measurements gives a peak density of ≈104 cm-3. The multiwavelength data characterise ISOSS 20246+6540 as a representative of a class of globules which has not been discovered so far due to their small angular size and low 100 μm brightness. A significant overabundance of 13CO is found X(13CO) ≥ 150 × X(C18O). This is likely due to isotope selective chemical processes.

Original languageEnglish
Pages (from-to)663-667
Number of pages5
JournalAstronomy and Astrophysics
Issue number2
Publication statusPublished - Nov 2002



  • Dust, extinction
  • ISM: clouds
  • ISM: molecules
  • Infrared: ISM
  • Surveys

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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