The AKARI/IRC mid-infrared all-sky survey^*

D. Ishihara^1,2, T. Onaka², H. Kataza³, A. Salama⁴, C. Alfageme^4**, A. Cassatella^4,5,6, N. Cox^4***, P. García-Lario⁴, C. Stephenson^4†, M. Cohen⁷, N. Fujishiro^3,8‡, H. Fujiwara², S. Hasegawa³, Y. Ita⁹, W. Kim^3,2§, H. Matsuhara³, H. Murakami³, T. G. Müller¹⁰, T. Nakagawa³, Y. Ohyama¹¹, S. Oyabu³, J. Pyo¹², I. Sakon², H. Shibai¹³, S. Takita³, T. Tanabé¹⁴, K. Uemizu³, M. Ueno³, F. Usui³, T. Wada³, H. Watarai¹⁵, I. Yamamura³ and C. Yamauchi³

¹ Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-860, Japan e-mail: ishihara@u.phys.nagoya-u.ac.jp
² Department of Astronomy, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
³ Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan
⁴ European Space Astronomy Center (ESAC), Villanueva de la Cañada, PO Box 78, 28691 Madrid, Spain
⁵ INAF, Istituto di Fisica dello Spazio Interplanetario, via del Fosso del Cavaliere 100, 00133 Roma, Italy
⁶ Dipartimento di Fisica, Universita' Roma Tre, via della Vasca Navale 100, 00146 Roma, Italy
⁷ Radio Astronomy Laboratory, University of California, Berkeley, USA
⁸ Department of Physics, Faculty of Science, University of Tokyo, 3-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0003, Japan
⁹ National Astronomical Observatory of Japan, Mitaka, Tokyo, 181-8588, Japan
¹⁰ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrae, 85748 Garching, Germany
¹¹ Academia Sinica, Institute of Astronomy and Astrophysics (ASIAA), Taipei 10617, Taiwan
¹² Korea Astronomy and Space Science Institute (KASI), 61-1, Hwaam-dong, Yuseong-gu, Daejeon, 305-348, Republic of Korea
¹³ Graduate School of Science, Osaka University, 1-1, Machikaneyama, Toyonaka, Osaka, 560-0043, Japan
¹⁴ Institute of Astronomy, Faculty of Science, University of Tokyo, Mitaka, Tokyo, 181-8588, Japan
¹⁵ Space Applications Mission Directorate, Japan Aerospace Exploration Agency (JAXA), 2-1-1, Sengen, Tsukuba, Ibaraki, 305-8505, Japan

Received: 6 December 2009
Accepted: 17 February 2010

Abstract

Context. AKARI is the first Japanese astronomical satellite dedicated to infrared astronomy. One of the main purposes of AKARI is the all-sky survey performed with six infrared bands between 9 μm and 200 μm during the period from 2006 May 6 to 2007 August 28. In this paper, we present the mid-infrared part (9 μm and 18 μm bands) of the survey carried out with one of the on-board instruments, the infrared camera (IRC).

Aims. We present unprecedented observational results of the 9 μm and 18 μm AKARI all-sky survey and detail the operation and data processing leading to the point source detection and measurements.

Methods. The raw data are processed to produce small images for every scan, and the point sources candidates are derived above the 5σ noise level per single scan. The celestial coordinates and fluxes of the events are determined statistically and the reliability of their detections is secured through multiple detections of the same source within milli-seconds, hours, and months from each other.

Results. The sky coverage is more than 90% for both bands. A total of 877 091 sources (851 189 for 9 μm, 195 893 for 18 μm) are confirmed and included in the current release of the point source catalog. The detection limit for point sources is 50 mJy and 90 mJy for the 9 μm and 18 μm bands, respectively. The position accuracy is estimated to be better than 2''. Uncertainties in the in-flight absolute flux calibration are estimated to be 3% for the 9 μm band and 4% for the 18 μm band. The coordinates and fluxes of detected sources in this survey are also compared with those of the IRAS survey and are found to be statistically consistent.