SPECTRAL LINE SURVEY TOWARD A MOLECULAR CLOUD IN IC10

Abstract

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 the 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 13 CO lines, while the c -C 3 H 2 , CH 3 OH, CN, C 18 O, and N 2 H + lines are not detected. The spectral intensity pattern is found to be similar to those observed toward molecular clouds in the Large Magellanic Cloud (LMC), 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 CH 3 OH may be deficient. These characteristic trends for CCH and CH 3 OH are also seen in the LMC, and seem to originate from photodissociation regions more extended in the peripheries of molecular clouds due to the lower metallicity condition.