We present hitherto the largest sample of gas-phase metallicity radial gradients measured at sub-kiloparsec resolution in star-forming galaxies in the redshift range of $zin[1.2, 2.3]$. These measurements are enabled by the synergy of slitless spectroscopy from the Hubble Space Telescope near-infrared channels and the lensing magnification from foreground galaxy clusters. Our sample consists of 76 galaxies with stellar mass ranging from 10$^7$ to 10$^{10}$ $M_odot$, instantaneous star-formation rate in the range of [1, 100] $M_odot$/yr, and global metallicity [$frac{1}{12}$, 2] solar. At 2-$sigma$ confidence level, 15/76 galaxies in our sample show negative radial gradients, whereas 7/76 show inverted gradients. Combining ours and all other metallicity gradients obtained at similar resolution currently available in the literature, we measure a negative mass dependence of $Deltalog({rm O/H})/Delta r~ [mathrm{dex~kpc^{-1}}] = left(-0.020pm0.007right) + left(-0.016pm0.008right) log(M_ast/10^{9.4} M_odot)$ with the intrinsic scatter being $sigma=0.060pm0.006$ over four orders of magnitude in stellar mass. Our result is consistent with strong feedback, not secular processes, being the primary governor of the chemo-structural evolution of star-forming galaxies during the disk mass assembly at cosmic noon. We also find that the intrinsic scatter of metallicity gradients increases with decreasing stellar mass and increasing specific star-formation rate. This increase in the intrinsic scatter is likely caused by the combined effect of cold-mode gas accretion and merger-induced starbursts, with the latter more predominant in the dwarf mass regime of $M_astlesssim10^9 M_odot$.
Download