Molecular Gas in the Low Metallicity , Star Forming Dwarf Ic

We present a complete survey of CO (1 → 0) emission in the Local Group dwarf irregular IC 10. The survey, conducted with the BIMA interferometer, covers the stellar disk and a large fraction of the extended H I envelope with the sensitivity and resolution necessary to detect individual giant molecular clouds (GMCs) at the distance of IC 10 (950 kpc). We find 16 clouds with a total CO luminosity of 1 × 10 6 K km s −1 pc 2 , equivalent to 4 × 10 6 M ⊙ of molecular gas using the Galactic CO-to-H 2 conversion factor. Observations with the ARO 12m find that BIMA may resolve out as much as 50% of the CO emission, and we estimate the total CO luminosity as ∼ 2.2 × 10 6 K km s −1 pc 2. We measure the properties of 14 GMCs from high resolution OVRO data. These clouds are very similar to Galactic GMCs in their sizes, line widths, luminosities, and CO-to-H 2 conversion factors despite the low metallicity of IC 10 (Z ≈ 1/5Z ⊙). Comparing the BIMA survey to the atomic gas and stellar content of IC 10 we find that most of the CO emission is coincident with high surface density H I. IC 10 displays a much higher star formation rate per unit molecular (H 2) or total (H I + H 2) gas than most galaxies. This could be a real difference or may be an evolutionary effect — the star formation rate may have been higher in the recent past.