15 micron Infrared Space Observatory observations of the 1415+52 Canada-France Redshift Survey field: The cosmic star formation rate as derived from deep ultraviolet, optical, mid-infrared, and radio photometry

The Canada-France Redshift Survey 1452+52 field has been deeply imaged with the Infrared Space Observatory using ISOCAM through the LW3 filter (12-18 mu m). Careful data analysis and comparison with deep optical and radio dat a have allowed us to generate a catalog of 78 15 mu m sources with both rad io and optical identifications. They are redder and lie at higher redshift than I-band selected galaxies, with most of them being star-forming galaxie s. We have considered the galaxies detected at radio and 15 mu m wavelength s, which potentially include all strong and heavily extincted starbursts, u p to z = 1. Spectral energy distributions (SEDs) for each of the sources ha ve been derived using deep radio, mid-IR, near-IR, optical, and UV photomet ry. The sources were then spectrally classified by comparing with SEDs of w ell-known nearby galaxies. By deriving their far-IR luminosities by interpo lation, we can estimate their star formation rate (SFR) in a way that does not depend sensitively on the extinction. Between 35% and 85% of the star f ormation at z I 1 is related to IR emission, and the global extinction is i n the range A(v) = 0.5-0.85. While heavily extincted starbursts with SFRs i n excess of 100 M. yr(-1) constitute less than 1% of all galaxies, they con tribute about 18% of the SFR density out to z = 1. Their morphologies range from S0 to Sab, and more than a third are interacting systems. The SFR der ived by far-IR fluxes is likely to be similar to 2.9 times higher than thos e previously estimated from UV fluxes. The derived stellar mass formed sinc e the redshift of 1 could be too high when compared with the present-day st ellar mass density. This might be due to an initial mass function in distan t star-forming galaxies different from the solar neighborhood one or an und erestimate of the local stellar mass density.