2026A&A...705A.236M

Aims. We present the redshift evolution of radial color gradients (in rest-frame U - V and V - J) for galaxies in the range 0.5 < z < 2.5 and investigate their origin and the dependence on stellar mass.
Methods. We selected ≈10 200 galaxies with stellar masses M_★ > 10^9.5 M_⊙ from publicly available JWST/NIRCam-selected catalogs. Using 2D Sérsic profile fits to account for point spread function broadening, we performed a spatially resolved spectral energy distribution fitting on HST and JWST/NIRCam photometry to retrieve accurate rest-frame U - V and V - J color gradients within 2 R_e, F444W_.
Results. The generally negative V - J color gradients of star-forming galaxies strongly depend on mass and redshift. For massive star-forming galaxies (M_★ > 10^10.5 M_⊙) at z > 1.5, the V - J colors are ≈0.5 mag redder within the effective radius than outside on average. At all redshifts and throughout the entire stellar mass range, the V - J gradients strongly correlate with global attenuation (A_V), which suggests that they predominantly trace dust attenuation gradients. Edge-on galaxies are redder and have stronger gradients at all z, although the correlation weakens at higher z. The U - V and V - J color gradients in the quiescent galaxy population, in contrast, are weakly negative (from ≈ - 0.1 to ≈ - 0.2 mag) but significant, and they depend little or not at all on stellar mass, redshift, or axis ratio. The implication is that quiescent galaxies must be largely transparent, with low A_V, and their color gradients are mostly attributable to stellar population gradients.