All Figures

Figure 1: The distribution by types of the (R< 20.5) ISO-ESS galaxies, derived from the optical spectral classification (de Lapparent et al. 2003). The dominant population is Sb-Sbc spirals, confirming that ellipticals are rarely detected at 12 m. Note, however, that among the 104 galaxies detected at m in the area common to both surveys, only 77 have ESS spectroscopic information (hence redshift and spectral type), leaving room for the discovery of new populations and signatures of evolution.

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In the text

Figure 2: Cumulative 12 m galaxy counts observed with the LW10 filter from the ISO-ESS survey, plotted as full squares with error bars. The other ISOCAM 15 m surveys are also plotted: the compilation by Elbaz et al. (1999) as a solid line contour, which covers the Lockman Hole (Rodighiero et al. 2004), the Marano field (Aussel et al. 1999), and the HDF North and South fields (Altieri et al. 1999) to various depths; the number-counts from the ELAIS survey (La Franca et al. 2004) are shown as a dotted line. The 15 m flux densities are corrected to 12 m, see text for details.

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In the text

Figure 3: The ISO-ESS 12 m differential counts normalised to the Euclidean case, plotted as filled squares (note that is positive). The other 15 m surveys are also shown: ELAIS-S1 (Pozzi et al. 2003, triangles); through the cluster-lens A2390 (Altieri et al. 1999, 6-pointed open star), HDF North (Aussel et al. 1999, crosses); HDF South (asterisks), Marano FIRBACK Ultra Deep field (open squares), Marano Ultra Deep ROSAT field (points), Marano Deep field (open circles), all published in Elbaz et al. (1999); Lockman Deep field (4-pointed open star), Lockman Shallow field (3-pointed heavy cross), both from Rodighiero et al. (2004). See text for the details of the correction from 15 m to 12 m.

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In the text

	Figure 4: Example of the strong evolution in the SEDs predicted by PÉGASE.3 for a star forming galaxy spiral Sc at various ages (increasing upwards), in the wavelength interval 1000 Å to 1 cm. (See more details in Fioc et al. 2007.)
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In the text

Figure 5: The predictions of 12 m cumulative galaxy counts (heavy line) calculated from model 1 of normal galaxies ( left) and model 2 with 9% of ULIRGs ( right): see Table 1, Cols. 7 and 8. They are compared to the observed 12 m cumulative counts from the ISO-ESS survey (black squares). The models with the cosmological k-correction only (no evolution correction: heavy dashed line) and the models with only the elemental comoving volume effect (dotted line) are also plotted for comparison. The faint counts from the 15 m surveys are shown with the same line coding as in Fig. 2.

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In the text

Figure 6: The predictions of Euclidean-normalised differential 12 m galaxy counts, calculated with model 1 (normal, left) and model 2 (including ULIRGs, right) using PÉGASE.3 (solid line), are compared to the observed differential counts at 12 m from the ISO-ESS survey (black squares). The cases without evolution (only cosmological k-correction) are shown with a dashed line, the case without k+e corrections (only the comoving volume effect) with a dotted line. The symbol coding for the 15 m surveys is the same as in Fig. 3.

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In the text

Figure 7: Cumulative 24 m faint galaxy counts (solid line) predicted by model 1 (normal, left) and model 2 (with ULIRGs, right) using PÉGASE.3 (the same models as for the interpretation of the ISO 12 m counts), are compared to the Spitzer/MIPS/24 m observations by Papovich et al. (2004). The luminosity function is from IRAS/25 m (Shupe et al. 1998). As in previous figures, the dashed line is for counts taking into account only the k-correction and volume expansion effect, while the dotted line corresponds to the comoving volume correction only (no k+e correction).

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In the text

Figure 8: The differential 24 m faint galaxy counts computed with PÉGASE.3 (solid line) for model 1 with only normal galaxies ( left) and model 2 with ULIRGs ( right), both compared to the SPITZER/MIPS/24 m observations of Papovich et al. (2004). The other symbols are identical to the previous figure. For the 24 m filter, the k-correction line (dashed line, left) appears below the comoving volume line because the k-correction is negative, as shown by the SEDs displayed in Fig. 4.

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In the text

Figure 9: Histories of the cosmic star-formation rate density (global and by types) derived from models of galaxy populations that fit optical and IR faint galaxy counts. The total SFR(z) (heavy solid line) summed on all types is shown. The three (thin lines) correspond to: 1) the major SFR at high reshifts (z>4) is from E/SO galaxies, it induces the bulk of stars at early epochs 2) the intermediate SFR is from early spirals (Sa-Sbc), dominant from z=0.6 to 4; it also fits the slope of the I-selected CFRS observations (empty circles), up to z=1 before incompletness. 3) the weakest SFR is from Sc-Im galaxy types (late-type spirals and irregulars), dominant at where late galaxies are numerous and, still gas-rich, forming stars (see also Rocca-Volmerange 1999).

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In the text