The Rise and Fall of Star-Forming Clumps: Formation and Evolution of the Building Blocks of Galaxies Across Cosmic Time

Abstract

It is well established that many high-redshift star-forming galaxies host massive, clumpy regions of intense star formation. However, the physical mechanisms responsible for clump formation remain uncertain, largely due to the lack of observations directly linking clump properties to their formation processes.

In this dissertation, we investigate clump formation and evolution through three complementary studies. First, we test whether clump formation is associated with the accretion of metal-poor gas, which is expected to dilute a galaxy’s gas-phase metallicity. Using GNIRS spectroscopy from the Gemini-North telescope, we measure gas-phase metallicities for a small sample (<30) of clumpy and nonclumpy galaxies. We find that clumpy galaxies exhibit systematically lower metallicities relative to the mass–metallicity relation, consistent with clump formation driven by gas inflow.

The second study uses resolved imaging from the James Webb Space Telescope CANUCS extragalactic fields to characterize clump populations and their mass distributions. We show that the slope of the aggregated clump mass function is consistent with clumps forming in-situ, but varies with host galaxy mass, becoming flatter in more massive systems and steeper in lower-mass galaxies. We also find that the clump mass function flattens with clump age, likely suggesting mechanisms effecting clump evolution.

Finally, we combine spectroscopic and photometric data to extend our analysis to a larger sample of 300 star-forming galaxies. We find that clumpy galaxies with lower gas-phase metallicities tend to host younger, more actively star-forming clumps. Together, the results of this dissertation provide the first cohesive observational evidence linking gas accretion, clump formation, and clump evolution in high-redshift galaxies.