Speaker
Description
The evolution of galaxy sizes allows us to constrain galaxy formation models. Crucially, JWST now provides the ability to observe the build-up of galaxies at the Epoch of Reionisation (EoR) in the rest-frame optical, granting the ability to observe the impacts of the first episode(s) of star formation on galaxy sizes. We analyse the sizes of H$\alpha$-selected star-forming galaxies at z = 6.1 from the JWST Emission Line Survey (JELS) in both broadband F444W and narrowband F466N & F470N NIRCam images at $\sim$ 4.4 - 4.7 $\mu$m. By modelling with GALFIT, we find a size-mass relationship that is $\approx$ -0.4 dex offset from the van der Wel et al. (2014) equivalent at z = 2.75, but with a similar power-law slope. By combining our results with the literature, we infer that the half-light radii, r$_{e}$, of $M_{*} = 10^{9.25}$ M$_{\odot}$ star-forming galaxies increases by $\sim$ 0.7 kpc/Gyr between the EoR and Cosmic Noon, but only ∼0.2 kpc/Gyr between z = 2.75 and z = 0.25. For the same stellar mass, we find an average r$_{e}$ = 0.77 $\pm$ 0.19 kpc at z = 6.1, which is in excellent agreement with galaxy evolution models. We find a ratio between the sizes of the galaxy and its star-forming region of 1.19 $\pm$ 0.11. This suggests star-forming galaxies must have already gone through a period of significant star formation to form these stellar disks.
