We present the first results on the spatial distribution of star formation in 454 star-forming galaxies at $4.8<z<6.5$ using H-Alpha emission-line maps and F444W imaging tracing the stellar continuum from JWST FRESCO NIRCam Slitless Spectroscopy. Star-forming galaxies with stellar masses 6.8≤log(M*/M_)$<11.1$ have positive H-Alpha equivalent width profiles, providing direct evidence for the inside-out growth of galaxies just after the epoch of reionisation. GALFIT is used to calculate half-light radii, Reff and central surface densities within 1 kiloparsec, Σ1kpc. At a fixed stellar mass of log(M*/M_)=9.5, Σ1kpc, Hα is 1.04±0.05 times higher than Σ1kpc, C, Reff, Hα is 1.18±0.03 times larger than Reff, C and both Reff measurements are less than 1 kiloparsec. These measurements suggest the rapid build-up of compact bulges just after the epoch of reionisation. By comparing to work done at lower redshifts with HST WFC3 Slitless Spectroscopy as part of the 3D-HST ($z=1$) and CLEAR ($z=0.5$) surveys, we find that Reff(z) evolves at the same pace for Hα and the continuum, but Σ1kpc(z) evolves faster for Hα. As a function of the Hubble parameter, Reff, HαReff, C=1.1h(z) and Σ1kpc,HαΣ1kpc,C=h(z)1.3. These functions suggest that the inside-out growth of the disk dominates the inside-out growth of the bulge towards lower redshifts. This is supported by the redshift evolution in EW(Hα) profiles, where there is rapid increase in EW(Hα) with radius within the half-light radius at $z=5.3$ but only significantly increasing EW(Hα) with radius in the outer disk at $z=0.5$.
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Matharu et al. (2024) studied this question.