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 μm 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 {S}450μ {{m}}={23.5}-8.1+26.8 μJy and intrinsic CO luminosities {L}{CO(3-2)}{\prime }={2.90}-0.23+0.21 × {10}8 {{K}} {km} {{{s}}}-1 {{pc}}2 and {L}{CO(6-5)}{\prime }={8.0}-1.3+1.4× {10}7 {{K}} {km} {{{s}}}-1 {{pc}}2. We used the resolved properties in the source plane to obtain molecular gas and star formation rate surface densities of {{{Σ }}}{{H}2}={16.2}-3.5+5.8 {M}⊙ {{pc}}-2 and {{{Σ }}}{SFR}={0.54}-0.27+0.89 {M}⊙ {{yr}}-1 {{kpc}}-2, 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 J∼ 5, with a higher excitation concentrated in the star-forming clumps.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2017
- DOI:
- 10.3847/2041-8213/aa87af
- arXiv:
- arXiv:1708.07898
- Bibcode:
- 2017ApJ...846L..22G
- Keywords:
-
- galaxies: individual: RCSGA 032727–132609;
- gravitational lensing: strong;
- submillimeter: ISM;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 11 pages, 4 figures, accepted for publication in ApJL