The Size and Shape Evolution of Galaxies using the James Webb Space Telescope

Abstract

In this dissertation, the results of a size and structural analysis of 1395 galaxies at 0.5 < z < 8 with stellar masses log ( M_star /M_solar )> 9.5 within the JWST CEERS field overlapping with the HST CANDELS EGS observations are presented. The light profile fitting software GALFIT is used to fit single Sersic models to the rest-frame optical profile of the galaxies within a mass selected sample. The primary result indicates that when observed at their rest-frame optical wavelength, galaxies become progressively smaller, evolving as ~ (1 + z)^(-0.71 +/- 0.19) since z ~ 8. The majority of massive galaxies at high redshifts possess low Sersic indices and thus do not feature steep, concentrated light profiles. Additionally, an exploration into the evolution of the size-stellar mass relationship is conducted, revealing a correlation where more massive systems are larger up to z ~ 6. However, this relationship becomes less clear at z > 3, with galaxies being of similar sizes regardless of their star formation rates, and varying less with mass. The analysis demonstrates that galaxies are more compact at redder wavelengths, independent of sSFR or stellar mass up to z ~ 3. Furthermore, it is shown that the size evolution of galaxies continues up to z ~ 8, emphasising that the process or causes for this evolution are active at early times. These results, and possible galaxy evolution processes at early epochs are discussed.

Date of Award	1 Aug 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Christopher Conselice (Supervisor) & Rowan Smith (Supervisor)