Deep far infrared ISOPHOT survey in "Selected Area 57" - I. Observations and source counts

M.J.D. Linden-Vornle, Hans Ulrik Nørgaard-Nielsen, H.E. Jørgensen, Lene Hansen, M. Haas, U. Klaas, P. Abraham, D. Lemke, Ib Lundgaard Rasmussen, H.W. Schnopper

Research output: Contribution to journalJournal articleResearchpeer-review


We present here the results of a deep survey in a 0.4 deg(2) blank field in Selected Area 57 conducted with the ISOPHOT instrument aboard ESAs Infrared Space Observatory (ISO1) at both 60 mu m and 90 mu m. The resulting sky maps have a spatial resolution of 15 x 23 arcsrc(2) per pixel which is much higher than the 90 x 90 arcsec(2) pixels of the IRAS All Sky Survey. We describe the main instrumental effects encountered in our data, outline our data reduction and analysis scheme and present astrometry and photometry of the detected point sources. With a formal signal to noise ratio of 6.75 we have source detection limits of 90 mJy at 60 mu m and 50 mJy at 90 mu m To these limits we find cumulated number densities of 5+/-3.5 deg(-2) at 60 mu m and 14.8+/-5.0 deg(-2) at 90 mu m. These number densities of sources are found to be lower than previously reported results from ISO but the data do not allow us to discriminate between no-evolution scenarios and various evolutionary models.
Original languageEnglish
JournalAstronomy & Astrophysics
Issue number1
Pages (from-to)51-64
Publication statusPublished - 2000


  • galaxies : starburst
  • infrared : galaxies
  • galaxies : evolution

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