Spectral Line Survey toward a Molecular Cloud in IC10
  We have conducted a spectral line survey observation in the 3 mm band toward
the low-metallicity dwarf galaxy IC10 with the 45 m radio telescope of Nobeyama
Radio Observatory to explore its chemical composition at a molecular-cloud
scale (~80 pc). The CS, SO, CCH, HCN, HCO+, and HNC lines are detected for the
first time in this galaxy in addition to the CO and 13CO lines, while c-C3H2,
CH3OH, CN, C18O, and N2H+ lines are not detected. The spectral intensity
pattern is found to be similar to those observed toward molecular clouds in the
Large Magellanic Cloud, whose metallicity is as low as IC10. Nitrogen-bearing
species are deficient in comparison with the Galactic molecular clouds due to a
lower elemental abundance of nitrogen. CCH is abundant in comparison with
Galactic translucent clouds, whereas CH3OH may be deficient. These
characteristic trends for CCH and CH3OH are also seen in the LMC, and seem to
originate from photodissociation regions more extended in peripheries of
molecular clouds due to the lower metallicity condition.
