Sharda, P.da Cunha, ElisabeteFederrath, ChristophSwinbank, A. M.Dye, S.2021-05-112021-05-110035-8711http://hdl.handle.net/1885/232646Using high-resolution (sub-kiloparsec scale) data obtained by ALMA, we analyse the star formation rate (SFR), gas content, and kinematics in SDP 81, a gravitationally lensed starburst galaxy at redshift 3. We estimate the SFR surface density (ΣSFR) in the brightest clump of this galaxy to be 357+135−85M⊙yr−1kpc−2, over an area of 0.07 ± 0.02 kpc2. Using the intensity-weighted velocity of CO (5–4), we measure the turbulent velocity dispersion in the plane of the sky and find σv, turb = 37 ± 5 km s−1 for the clump, in good agreement with previous estimates along the line of sight. Our measurements of the gas surface density, freefall time, and turbulent Mach number allow us to compare the theoretical SFR from various star formation models with that observed, revealing that the role of turbulence is crucial to explaining the observed SFR in this clump. While the Kennicutt–Schmidt (KS) relation predicts an SFR surface density of ΣSFR, KS = 52 ± 17 M⊙ yr−1 kpc−2, the single-freefall model by Krumholz, Dekel, and McKee (KDM) predicts ΣSFR, KDM = 106 ± 37 M⊙ yr−1 kpc−2. In contrast, the multifreefall (turbulence) model by Salim, Federrath, and Kewley (SFK) gives ΣSFR,SFK=491+139−194M⊙yr−1kpc−2. Although the SFK relation overestimates the SFR in this clump (possibly due to the negligence of magnetic fields), it provides the best prediction among the available models. Finally, we compare the star formation and gas properties of this galaxy to local star-forming regions and find that the SFK relation provides the best estimates of SFR in both local and high-redshift galaxies.PS acknowledges travel support from the International Programmes and Collaboration Division, Birla Institute of Technology and Science, Pilani, India.5 CF acknowledges funding provided by the Australian Research Council’s Discovery Projects (grants DP150104329 and DP170100603), the Australian National University Futures Scheme, and the Australia-Germany Joint Research Cooperation Scheme [Universities Australia-German Academic Exchange Service (DAAD)]. EdC gratefully acknowledges the Australian Research Council for funding support as the recipient of a Future Fellowship (FT150100079). SD is a Rutherford Fellow supported by the UK Science and Technology Facilities Council.application/pdfen-AUTurbulenceStars: formationgalaxies: high-redshiftgalaxies: starburstGalaxy: kinematics and dynamicsSubmillimetre: galaxies2018-04-0710.1093/mnras/sty8862020-11-23