Deep Galaxy survey at 6.75mu M with the ISO satellite
Elbaz, D.; Omont, A.; Eales, S.; Le Fèvre, O.; Lilly, S. J.; Flores, H.; Hammer, F.; Crampton, D.; Désert, F. X.; Césarsky, C.; Thuan, T.
France, United States, Canada, United Kingdom
Abstract
Deep 6.75mu m mid-IR ISOCAM observations were obtained from the Canada-France Redshift Survey (CFRS) 1415+52 field with the Infrared Space Observatory. The identification of the sources with optical counterparts is described in detail, and a classification scheme is devised which depends on the S/N of the detection and the inverse probability of chance coincidence. 83% of the 54 ISOCAM sources are identified with IAB <23.5 counterparts. The (I-K)AB colors, radio properties, spectrophotometric properties and frequency of nuclear activity of these counterparts differ on average from those of typical CFRS galaxies. CFRS spectra are available for 21 of the sources which have IAB <= 22.5 (including 7 stars). Most of the strongest sources are stars or AGN. Among the non-stellar counterparts with spectra, 40% are AGNs, and 53% are galaxies that display star formation activity and/or significant contributions of A stars. The ISOCAM sources also display an IR excess, even when compared with heavily-reddened local starburst galaxies. An upper limit of 30% of extragalactic ISO sources could be at z > 1 of the 44 S_{6.75microns } > 150mu Jy sources which are non-stellar (7 "spectroscopic" and 3 "photometric" stars excluded). Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the countries: France, Germany, the Netherlands and the United Kingdom) with the participation of ISAS and NASA.