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H. Aussel (IfA), D.M. Alexander (PSU)
We present a reanalysis of the identifications of the Faint Source Catalog at 12 microns. We selected our sample above a flux of 0.2~Jy and at galactic latitudes |b| \ge 5o. Our aim is to build a local luminosity function. With respect to previous work, we introduce several improvements~: 1) the sample is directly selected at 12~microns, in order to avoid introducing some incompleteness due to the relative sensitivites with the other bands. 2) No selection according to the IRAS colors was performed. This enable us to retain in our sample, galaxies with little emission at longer wavelength. 3) A special care was given to IRAS photometry, with cross checks obtained from ISOCAM observations.
Our original sample consist in about 81000 objects, mainly galactic stars (80000) and galaxies (1000). In order to discriminate between the two, we have carefully taken into account IRAS position error ellipses, and possible counterparts in the Simbad, Tycho-2 and 2MASS databases. We have built for stars empirical relations between optical/NIR and MIR that prove extremely useful to identify the correct counterpart. These have been tested against stellar atmosphere models, and can be used to predict the mid-infrared flux of a star with a reasonable accuracy (10%). They are also a powerful tool to select stars with excess in the infrared. Our final observed extragalactic number counts agrees with the ones modeled by Xu et al. (1999), but are significantly lower than the ones derived by Rush et al (1992).
This research was supported by the JCMT fellowship and European TMR grants.
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The author(s) of this abstract have provided an email address for comments about the abstract: aussel@ifa.hawaii.edu