2019ApJ...879...52S

We present ∼1'' resolution (∼2 kpc in the source plane) observations of the CO (1-0), CO (3-2), Hα, and [N II] lines in the strongly lensed z = 2.26 star-forming galaxy SDSS J0901+1814. We use these observations to constrain the lensing potential of a foreground group of galaxies, and our source-plane reconstructions indicate that SDSS J0901+1814 is a nearly face-on (i ≃ 30°) massive disk with r_1/2 >= 4 kpc for its molecular gas. Using our new magnification factors (µ_tot ≃ 30), we find that SDSS J0901+1814 has a star formation rate (SFR) of 268_–61⁺⁶³M_☉yr^–1, M_gas=(1.6_–0.2^+0.3)×10¹¹(α_CO/4.6)M_☉, and M_*=(9.5_–2.8^+3.8)×10¹⁰M_☉, which places it on the star-forming galaxy "main sequence." We use our matched high angular resolution gas and SFR tracers (CO and Hα, respectively) to perform a spatially resolved (pixel-by-pixel) analysis of SDSS J0901+1814 in terms of the Schmidt-Kennicutt relation. After correcting for the large fraction of obscured star formation (SFR_Hα/SFR_TIR=0.054_–0.014^+0.015), we find that SDSS J0901+1814 is offset from "normal" star-forming galaxies to higher star formation efficiencies independent of assumptions for the CO-to-H₂ conversion factor. Our mean best-fit index for the Schmidt-Kennicutt relation for SDSS J0901+1814, evaluated with different CO lines and smoothing levels, is {bar}n=1.54±0.13; however, the index may be affected by gravitational lensing, and we find {bar}n=1.24±0.02 when analyzing the source-plane reconstructions. While the Schmidt-Kennicutt index largely appears unaffected by which of the two CO transitions we use to trace the molecular gas, the source-plane reconstructions and dynamical modeling suggest that the CO (1-0) emission is more spatially extended than the CO (3-2) emission.