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A Deep 12 $\rm\mu m$ Survey with ISO

D.L. Clements 1, F-X. Désert , A. Franceschini , W.T. Reach , A.C. Baker , J.K. Davies , & C. Cesarsky 

1 Institut d'Astrophysique Spatiale, Orsay, France




We present the first results of a study of faint 12 micron 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 sigma flux limit of about 500 microJy. From optical identifications based on the USNO catalogue and analysis of the optical/IR colours and 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 microns, and with models of the 12 $\rm\mu m$ source population. In particular, we find evidence for significant evolution in the galaxy population, with the no-evolution case excluded at the 3.5 $\rm\sigma$ level, and that the stellar population is well matched by existing models. Two of the objects detected at 12 $\rm\mu m$ are associated with known galaxies. One of these is an IRAS galaxy at $\rm z = 0.11$ with a luminosity of $\rm 10^{11} L_{\odot}$.

next up previous contents index
Next: ISO imaging of Gamma-ray Up: Poster session F Cosmology Previous: Mid-infrared number counts and
"The Universe as seen by ISO", 20 - 23 October 1998, Paris: Abstract Book