EDP Sciences
Free access
Volume 382, Number 2, February I 2002
Page(s) 600 - 609
Section Diffuse matter in space
DOI http://dx.doi.org/10.1051/0004-6361:20011626

A&A 382, 600-609 (2002)
DOI: 10.1051/0004-6361:20011626

Diffuse far-infrared [ $\ion{C}{ii}$] line emission from high Galactic latitude

S. Makiuti1, H. Shibai2, T. Nakagawa1, H. Okuda3, K. Okumura4, H. Matsuhara1, N. Hiromoto5 and Y. Doi6

1  The Institute of Space and Astronautical Science (ISAS), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan
2  Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
3  Gunma Astronomical Observatory, 6860-86 Nakayama, Takayama, Agatsuma Gunma, 377-0702, Japan
4  Communications Reserch Laboratory, 4-2-1 Nukui-kitamachi, Koganei, Tokyo 184-8795, Japan
5  Kansai Advanced Research Center, Communications Research Laboratory, 588-2 Iwaoka, Nishi-ku, Kobe 651-2492, Japan
6  College of Arts and Sciences, University of Tokyo, Komaba 3-8-1, Meguro, Tokyo 153-8902, Japan

(Received 23 July 2001 / Accepted 30 October 2001 )

The Far-Infrared Line Mapper (FILM) onboard the Infrared Telescope in Space (IRTS) made a survey for the far-infrared [ $\ion{C}{ii}$] 158 $\mu$m line emission with high sensitivity and moderate spatial resolution. We have found that diffuse [ $\ion{C}{ii}$] line emission extends to high Galactic latitude regions. The [ $\ion{C}{ii}$] line intensity at $\vert b\vert \sim 60^{\circ}$ ranges from $2\times10^{-7}$ to $1.5\times10^{-6}$  $\mbox{erg cm}^{-2}~\mbox{ s}^{-1}~\mbox{sr}^{-1}$. Comparisons of the distribution of the [ $\ion{C}{ii}$] line emission with those of the $\ion{H}{i}$ column density and far-infrared radiation show some correlations, but the [ $\ion{C}{ii}$] line emission differs from the far-IR and HI emission at high Galactic latitudes. These differences suggest that the [ $\ion{C}{ii}$] line primarily comes from ionized gas in the high-latitude regions. The intensities of the [ $\ion{C}{ii}$] line emission on the southern side ( $b < 0^{\circ}$) of the Galactic plane are systematically larger than those on the northern side ( $b > 0^{\circ}$). We infer from this difference that there is a displacement of the Sun with respect to the center of interstellar medium from which the [ $\ion{C}{ii}$] line comes. When an exponential distribution is assumed for the [ $\ion{C}{ii}$] emitting gas, it is expected that the Sun is located at the distance of about 17% of the scale height above the center of the gas. This is consistent with the previously reported displacement of the Sun from the Galactic plane.

Key words: lnfrared: ISM -- ISM: lines and bands -- ISM: structure -- Galaxy: general

Offprint request: S. Makiuti, makiuti@ir.isas.ac.jp

© ESO 2002