Resolving Star Formation on Subkiloparsec Scales in the High-redshift Galaxy SDP.11 Using Gravitational Lensing Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA

• Published in: The Astrophysical journal 2018-11, Vol.867 (2)
• Main Authors: Lamarche, C., Verma, A., Vishwas, A., Stacey, G. J., Brisbin, D., Ferkinhoff, C., Nikola, T., Higdon, S. J. U., Higdon, J., Tecza, M.
• Format: Article
• Language: English
• Subjects: galaxies: evolution; galaxies: high-redshift; galaxies: ISM; galaxies: star formation; H II regions; photon-dominated region (PDR)
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aae394

We investigate the properties of the interstellar medium, star formation, and the current-day stellar population in the strongly lensed star-forming galaxy H-ATLAS J091043.1-000321 (SDP.11), at z = 1.7830, using new Herschel and Atacama Large Millimeter/submillimeter Array (ALMA) observations of far-infrared fine-structure lines of carbon, oxygen, and nitrogen. We report detections of the [O iii] 52 m, [N iii] 57 m, and [O i] 63 m lines from Herschel/PACS, and present high-resolution imaging of the [C ii] 158 m line, and underlying continuum, using ALMA. We resolve the [C ii] line emission into two spatially offset Einstein rings, tracing the red and blue velocity components of the line, in the ALMA/Band 9 observations at 0 2 resolution. The values seen in the [C ii]/far-infrared (FIR) ratio map, as low as ∼0.02% at the peak of the dust continuum, are similar to those of local ULIRGs, suggesting an intense starburst in this source. This is consistent with the high intrinsic FIR luminosity (∼3 × 1012 L ), ∼16 Myr gas depletion timescale, and 8 Myr timescale since the last starburst episode, estimated from the hardness of the UV radiation field. By applying gravitational lensing models to the visibilities in the uv-plane, we find that the lensing magnification factor varies by a factor of two across SDP.11, affecting the observed line profiles. After correcting for the effects of differential lensing, a symmetric line profile is recovered, suggesting that the starburst present here may not be the result of a major merger, as is the case for local ULIRGs, but instead could be powered by star formation activity spread across a 3-5 kpc rotating disk.