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Astron. Astrophys. 328, L9-L12

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Letter to the Editor

ISOCAM 7 micron deep survey of the Lockman Hole:
A mid-infrared search for primeval galaxies*

Y. Taniguchi1, L.L. Cowie2, Y. Sato1,3, D.B. Sanders2, K. Kawara4, R. Joseph2, H. Okuda5, C.G. Wynn-Williams2, T. Matsumoto5, K.C. Chambers2, K. Wakamatsu6, F.X. Désert7, Y. Sofue4, and H. Matsuhara8

1 Astronomical Institute, Tohoku University, Aoba, Sendai 980-77, Japan
2 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
3 ISO Science Operations Centre, Astrophysics Division of ESA, Villafranca, E-28080 Madrid, Spain
4 Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181, Japan
5 Institute of Space and Astronautical Science, Yoshinodai, Sagamihara, Kanagawa 229, Japan
6 Department of Technology, Gifu University, 1-1 Yanagido, Gifu 501-11, Japan
7 Institut d'Astrophysique Spatiale, F-91405 Orsay, France
8 Department of Physics, Nagoya University, Furo, Chikusa, Nagoya 464, Japan

Received 12 August 1997 / Accepted 11 September 1997


We present results of our 7 µm deep survey program made with ISOCAM, the infrared camera of ISO (Infrared Space Observatory). We have found 15 sources above a 5 $\sigma_{\rm rms}$ significance in a small selected area ($3^\prime \times
3^\prime$) in the Lockman HI hole. Among the 15 sources, 14 objects have also been observed in the near infrared (NIR: $\sim 2 \mu$m). The majority of the 7 µm sources (11 objects) have NIR counterparts most of which are considered to be galaxies with intermediate redshifts. It is, however, intriguing that two 7 µm sources have no NIR counterpart. These objects may be heavily reddened populations which have not been detected by existing optical and NIR deep surveys.

Key words: galaxies: infrared emission - active galactic nuclei: infrared emission

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of ISAS and NASA.

Send offprint requests to: Y. Taniguchi

© European Southern Observatory (ESO) 1997

Online publication: November 24, 1997
Last change: March 26, 1998