Alma Resolves The Molecular Gas In A Young Low-Metallicity Starburst Galaxy At Z.=1.7

Abstract We present Atacama Large Millimeter/submillimeter Array observations of CO lines and dust continuum emission of the source RCSGA 032727–132609, a young z = 1.7 low-metallicity starburst galaxy. The CO(3–2) and CO(6–5) lines and continuum at rest-frame 450 μ m are detected and show a resolved structure in the image plane. We use the corresponding lensing model to obtain a source plane reconstruction of the detected emissions revealing an intrinsic flux density of μ Jy and intrinsic CO luminosities and . We used the resolved properties in the source plane to obtain molecular gas and star formation rate surface densities of and , respectively. The intrinsic properties of RCSGA 032727–132609 show an enhanced star formation activity compared to local spiral galaxies with similar molecular gas densities, supporting the ongoing merger–starburst phase scenario. RCSGA 032727–132609 also appears to be a low-density starburst galaxy similar to local blue compact dwarf galaxies, which have been suggested as local analogs to high-redshift low-metallicity starburst systems. Finally, the CO excitation level in the galaxy is consistent with having the peak at , with a higher excitation concentrated in the star-forming clumps.