A Census of Sub-kiloparsec Resolution Metallicity Gradients in
  Star-forming Galaxies at Cosmic Noon from HST Slitless Spectroscopy
  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 $z\in[1.2, 2.3]$. 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 $\Delta\log({\rm O/H})/\Delta r~
[\mathrm{dex~kpc^{-1}}] = \left(-0.020\pm0.007\right) +
\left(-0.016\pm0.008\right) \log(M_\ast/10^{9.4} M_\odot)$ with the intrinsic
scatter being $\sigma=0.060\pm0.006$ 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 $M_\ast\lesssim10^9 M_\odot$.
