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Far-Infrared [C II] Properties of Low-Metallicity Galaxies

Published online by Cambridge University Press:  14 August 2015

K. Mochizuki ,
T. Onaka  and
T. Nakagawa
K. Mochizuki
Affiliation:
Department of Astronomy, University of Texas Austin, TX 78712, USA
T. Onaka
Affiliation:
Department of Astronomy, University of Tokyo Bunkyou, Tokyo 113, Japan
T. Nakagawa
Affiliation:
The Institute of Space and Astronautical Science 3-1-1 Yoshinodai, Kanagawa 229, Japan

Extract

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The line flux ratio of the [C II] 158 μm fine-structure (2P3/2 → 2P3/2) emission to CO rotational emission is a probe of the intensity of the interstellar UV radiation in galaxies. The largest values for the [C II]/CO (J = 1-0) line ratios are found in starburst galaxies, none of which, however, show values larger than 6 ×103 (Stacey et al. 1991). The exception ([CII]/CO ≃ 2 × 104) are galaxies of Magellanic type which have low metallicity, an intense interstellar UV field, and irregular morphology (Table 1).

Mochizuki et al. (1994) showed that the two conditions, a low metallicity and an intense UV field are expected to result in the large [C II]/CO ratios in the Magellanic types. These conditions are likely to be common in more massive galaxies as well, but at an early epoch in their evolution. This suggests that bright [C II] emission can be a good indicator of young galaxies. However, the metal-poor galaxies previously observed in the [C II] line were exclusively Magellanic types. Observations of different types of dwarf galaxies are necessary to help us understand the physical conditions in the interstellar medium of low-metallicity systems.

Type
II. Joint Discussions
Information
Highlights of Astronomy , Volume 11 , Issue 1: Highlights of Astronomy. As presented at the XXIIIrd General Assembly of the IAU (Part A), 1997 , 1998 , pp. 123 - 124
Copyright
Copyright © Kluwer 1998

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