Abstract
Radial colour gradients within galaxies arise from gradients of stellar age, metallicity, and dust reddening. Large samples of colour gradients from wide-area imaging surveys can be used to constrain galaxy formation models. Here we measured colour gradients for low-redshift galaxies using photometry from the 9 th DESI Legacy Imaging Survey (LS), which reaches r ∼ 24 over ∼14,000 deg 2 . We investigate empirical relationships between colour gradients, M*, and sSFR. We compared our results with the prediction of the Illustris TNG-100 simulation using SDSS mock images.