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 ALMA observations of far-infrared fine-structure lines of carbon , oxygen and nitrogen .
We report detections of the [ O iii ] 52 \micron , [ N iii ] 57 \micron , and [ O i ] 63 \micron lines from Herschel/PACS , and present high-resolution imaging of the [ C ii ] 158 \micron 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 \farcs 2 resolution .
The values seen in the [ C ii ] /FIR ratio map , as low as \sim 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 ( \sim 3 \times 10 ^ { 12 } L _ { \odot } ) , \sim 16 Myr gas depletion timescale , and \lesssim 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 .