Spectral Line Survey toward a Molecular Cloud in IC10

TL;DR

This study conducted a spectral line survey of the low-metallicity galaxy IC10, revealing its molecular composition and chemical characteristics, which are similar to those in the Large Magellanic Cloud, highlighting effects of low metallicity on molecular abundances.

Contribution

First detection of several molecular lines in IC10 and comparison of its chemical composition with other low-metallicity environments.

Findings

Detected multiple molecular lines including CS, SO, CCH, HCN, HCO+, and HNC.

Nitrogen-bearing molecules are underabundant compared to the Milky Way.

CCH is relatively abundant, CH3OH is deficient, indicating effects of low metallicity.

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 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.