1999A&A...351L..37E

We present the results of the five mid-IR 15µm (12-18µm LW3 band) ISOCAM Guaranteed Time Extragalactic Surveys performed in the regions of the Lockman Hole and Marano Field. The roughly 1000 sources detected, 600 of which have a flux above the 80% completeness limit, guarantee a very high statistical significance for the integral and differential source counts from 0.1mJy up to ∼5mJy. By adding the ISOCAM surveys of the HDF-North and South (plus flanking fields) and the lensing cluster A2390 at low fluxes and IRAS at high fluxes, we cover four decades in flux from 50µJy to ∼0.3Jy. The slope of the differential counts is very steep (α=-3.0) in the flux range 0.4-4 mJy, hence much above the Euclidean expectation of α=-2.5. When compared with no-evolution models based on IRAS, our counts show a factor ∼10 excess at 400µJy, and a fast convergence, with α=-1.6 at lower fluxes.