Volume 405, Number 3, July III 2003
|Page(s)||833 - 849|
|Section||Cosmology (including clusters of galaxies)|
|Published online||30 June 2003|
A deep 6.7 m survey in the SSA13 field with ISO *
Institute of Space and Astronautical Science (ISAS), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan
2 Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
3 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
4 Astronomical Institute, Graduate School of Science, Tohoku University, Aramaki, Aoba, Sendai 980-8578, Japan
5 Max-Planck Institut fur Extraterrestrische Physik, 85740 Garching, Germany
6 Gunma Astronomical Observatory, 6860-86 Nakayama, Takayama, Agatsuma, Gunma 377-0702, Japan
7 Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
Corresponding author: Y. Sato, firstname.lastname@example.org
Accepted: 18 April 2003
We present results of a deep mid-infrared survey in the SSA13 field with the Infrared Space Observatory (ISO). In order to probe the near-infrared light at high redshifts, we surveyed the field with the broad band LW2 (5–8.5 μm) filter of the mid-infrared camera ISOCAM. Adopting a highly redundant imaging strategy for the 23 h observation and carefully treating gradual changes in the detector responsivity caused by a very high rate of cosmic ray impacts, we succeeded in reaching an 80% completeness limit of 16 μJy in the central 7 arcmin2 region. Utilizing the signal-to-noise ratio map, we detected 65 sources down to 6 μJy in the 16 arcmin2 field. Integral galaxy number counts at 6.7 μm are then derived, reaching deg-2 at the faint limit with a slope of -1.6 between 13 μJy and 130 μJy. Integrating individual sources in this flux range, the resolved fraction of the extragalactic background light at 6.7 μm is estimated to be 0.56 nW m-2 sr-1. These results, which reach a flux limit three times fainter than those in the Hubble Deep Fields, are in fairly good agreement with a model prediction by Franceschini et al. (1997). Finally, we discuss the relation of distant massive E/S0 galaxies to the faint 6.7 μm galaxy population.
Key words: Galaxy: evolution / infrared: galaxies / cosmology: observations / surveys / galaxies: photometry / methods: data analysis
© ESO, 2003
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