Effects of dust abundance on the far-infrared colours of blue compact
  dwarf galaxies
  We investigate the FIR properties of a sample of BCDs observed by AKARI. By
utilizing the data at wavelengths of $\lambda =65 \mu$m, 90 $\mu$m, and 140
$\mu$m, we find that the FIR colours of the BCDs are located at the natural
high-temperature extension of those of the Milky Way and the Magellanic Clouds.
This implies that the optical properties of dust in BCDs are similar to those
in the Milky Way. Indeed, we explain the FIR colours by assuming the same grain
optical properties, which may be appropriate for amorphous dust grains, and the
same size distribution as those adopted for the Milky Way dust. Since both
interstellar radiation field and dust optical depth affect the dust
temperature, it is difficult to distinguish which of these two physical
properties is responsible for the change of FIR colours. Then, in order to
examine if the dust optical depth plays an important role in determining the
dust temperature, we investigate the correlation between FIR colour (dust
temperature) and dust-to-gas ratio. We find that the dust temperature tends to
be high as the dust-to-gas ratio decreases but that this trend cannot be
explained by the effect of dust optical depth. Rather, it indicates a
correlation between dust-to-gas ratio and interstellar radiation field.
Although the metallicity may also play a role in this correlation, we suggest
that the dust optical depth could regulate the star formation activities, which
govern the interstellar radiation field. We also mention the importance of
submillimetre data in tracing the emission from highly shielded low-temperature
dust.
