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Astron. Astrophys. 346, 383-391 (1999)

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A deep 12 micron survey with ISO *

D.L. Clements 1, F-X. Desert 1,2, A. Franceschini 3, W.T. Reach1,4, A.C. Baker 5, J.K. Davies 6 and C. Cesarsky 5

1 Institut d'Astrophysique Spatiale, Batiment 121, Universite Paris XI, F-91405 Orsay Cedex, France
2 Laboratoire d'Astrophysique, Observatoire de Grenoble, B.P. 53, 414 rue de la piscine, F-38041 Grenoble Cedex 9, France
3 Dipartimento di Astronomia, Universita' di Padova, Padova, Italy
4 IPAC, Caltech, MS 100-22, Pasadena, CA 91125, USA
5 Service d'Astrophysique, Orme des Merisiers, Bat. 709, CEA/Saclay, F-91191 Gif-sur-Yvette Cedex, France
6 JACH, 660 N. Aokoku Place, University Park, Hawaii, HI 96720, USA

Received 3 September 1998 / Accepted 19 January 1999

Abstract

We present the first results of a study of faint 12 µm sources detected with the Infrared Space Observatory (ISO) in four deep, high galactic latitude fields. The sample includes 50 such sources in an area of 0.1 square degrees down to a 5[FORMULA] flux limit of [FORMULA]Jy. From optical identifications based on the US Naval Observatory (USNO) catalogue and analysis of the optical/IR colours and Digital Sky Survey (DSS) images, we conclude that 37 of these objects are galaxies and 13 are stars. We derive galaxy number counts and compare them with existing IRAS counts at 12 µm, and with models of the 12 µm source population. In particular, we find evidence for significant evolution in the galaxy population, with the no-evolution case excluded at the 3.5[FORMULA] level. The stellar population is well matched by existing models. Two of the objects detected at 12 µm are associated with known galaxies. One of these is an IRAS galaxy at z=0.11 with a luminosity of [FORMULA].

Key words: surveys – galaxies: evolution – infrared: galaxies – infrared: stars

* 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 Kingdon) and with the participation of ISAS and NASA

Send offprint requests to: D.L. Clements, Department of Physics and Astronomy, Cardiff University, PO Box 913, Cardiff CF2 3YB, UK

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© European Southern Observatory (ESO) 1999

Online publication: May 21, 1999
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