A multifrequency study of star formation in the blue compact dwarf galaxy IZw 36

Search for the [CII] 158 micron emission toward the blue compact dwarf galaxy I Zw 36

“…In order to obtain the [C ii]/CO line ratio, we selected an object previously detected in the CO J = 1−0 emission: I Zw 36 (Mrk 209; UGCA 281). This nearby ( 4.6 Mpc; e.g., Viallefond & Thuan 1983) galaxy has a lower metallicity (12 + log[O/H] = 7.9 in interstellar oxygen abundance; Viallefond & Thuan 1983) than the irregulars previously observed in the [C ii] emission. The comparison of I Zw 36 with the irregulars enables us to investigate the effect of galactic morphology on the C + -CO chemical balance in the low-metallicity environments.…”

“…3), which has a similar size to the optical area of the galaxy. Thus, the proposed high density does not conflict with the presence of a diffuse H i halo (Viallefond & Thuan 1983) extended to a diameter of 150 , where the gas density is possibly lower.…”

“…The [C ii]/CO line ratios for NGC 4449 and NGC 1569 are from Lord et al (1995). The references for the oxygen abundance are as follows: the inner Galaxy, Deharveng et al (2000); the LMC, Russell & Dopita (1990); NGC 4449 and IC 10, Hidalgo-Gámez & Olofsson (1998) based on observations of McCall et al (1985) and Lequeux et al (1979); NGC 1569, Kobulnicky & Skillman (1997); I Zw 36, Viallefond & Thuan (1983). The radial variation of metallicity in our Galaxy is taken into account; the lower and upper limits in the figure correspond to the abundances at the Galactocentric distance of the Sun and the extrapolation of the relation between the abundance and the Galactocentric distance to the Galactic center, respectively.…”

“…This method can underestimate the extinction by up to 1 mag (Donas et al 1987) because of oversimplified assumptions on the distribution of H i gas (Donas & Deharveng 1984). By comparison the extinction based on a line ratio toward the dominant H ii region (for a smaller aperture of 10 ×20 ) in I Zw 36 is 1.4 mag at λ = 1909Å (Viallefond & Thuan 1983). Accordingly, we calculated ratios also for G 0 = 10 1.5 as well as G 0 = 10 0.5 (Fig.…”

Formation and Evolution of Galaxies and Large Structures in the Universe

“…These latter are of particular interest , because they are characterized by the occurrence of very intense stellar activities at the present time , blue colours , high hydrogen cont ent s and low metal abundan ces . However , a few objects like IZW 18 (Lequeux and , 1980 ) and IZW 36 (Viallefond and Thuan , 1982) seem not to obey the above schematizat ion , as they posses both low metalli cities and low hydrogen to total ma ss ratios at the same time .…”