Galaxy populations from Deep ISO Surveys

I discuss some of the main extra-galactic field surveys which have been undertaken by the Infrared Space Observatory (ISO). I review the findings from the source counts analysies and then examine some of the more recent detailed investigations into the explicit nature of the populations that make up these source counts. Depending on how you count them, ISO (Kessler et al. 1996) undertook around fifteen independent field surveys to explore the extra-galactic populations. These surveys primarily used the ISO-PHOT (Lemke et al. (1996)) and ISO-CAM (Cesarsky et al. (1996)) instruments. As shown in Table 1 and illustrated in Figure 1 these surveys explored the full extent of ISO's parameter space in terms of wavelength, area and depth. This is an attempt to collect together some of the findings of these surveys. I will group the surveys by wavelength, since the populations explored at different wavelengths are expected to be somewhat different. 1.1 Mid IR surveys 6.7-15µm Surveys in this wavelength regime tend to pick up emission from hotter sources such as AGN or luminous starbursts, they also pick up " cirrus " emission from normal galaxies. While these bands are located far from the peak of the typical starbursts spectral energy distribution it has been noted that the PAH features which do fall in these bands can be used as a good measure of star-formation activity. Surveys in these bands are the HDF surveys in the North and South; CFRS; ELAIS; the ISOCAM guaranteed time Extra Galactic Surveys, the Comet fields, the Japanese Lockman and Selected Area surveys and the CAM parallel mode survey.