Astron. Astrophys. 359, 51-64 (2000)

Deep far infrared ISOPHOT survey in "Selected Area 57"

I. Observations and source counts

M.J.D. Linden-Vornle ^1,2, H.U. Norgaard-Nielsen ², H.E. Jorgensen ¹, L. Hansen ¹, M. Haas ³, U. Klaas ³, P. Ábrahám ³, D. Lemke ³, I. Lundgaard Rasmussen ² and H.W. Schnopper <sup>4

1</sup> Niels Bohr Institute for Astronomy, Physics and Geophysics, Astronomical Observatory, Juliane Maries Vej 30, 2100 Kobenhavn O, Denmark
² Danish Space Research Institute, Juliane Maries Vej 30, 2100 Kobenhavn O, Denmark
³ Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany
⁴ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

Received 29 October 1999 / Accepted 26 April 2000

Abstract

We present here the results of a deep survey in a 0.4 deg² blank field in Selected Area 57 conducted with the ISOPHOT instrument aboard ESAs Infrared Space Observatory (ISO ¹) at both 60 µm and 90 µm. The resulting sky maps have a spatial resolution of 15 23 arcsrc² per pixel which is much higher than the 90 90 arcsec² 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 µm and 50 mJy at 90 µm. To these limits we find cumulated number densities of 5 deg^-2 at 60 µm and 14.8 deg^-2 at 90 µm. 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.

Key words: infrared: galaxies galaxies: evolution galaxies: starburst

Send offprint requests to: M.J.D. Linden-Vornle (michael@astro.ku.dk)

SIMBAD Objects

Contents

• 1. Introduction
• 2. The ISOPHOT observations
  • 2.1. Non-linearity effects
  • 2.2. Responsivity drift of the individual C100 pixels
  • 2.3. Glitches affecting the data stream
  • 2.4. Chopper dependent signal offset
• 3. Data reduction
  • 3.1. Source extraction
  • 3.2. Flux calibration
  • 3.3. Analysis of the ISOPHOT Lockman Hole data
• 4. Discussion
• 5. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: June 30, 2000
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