Low-redshift analogues of cosmic noon galaxies as laboratories for clumpy star formation

Abstract

It has been established that a significant fraction of star formation at high-redshift occurs in clumpy galaxies. The properties of clumps and their formation mechanisms, however, remain highly debated. In this work we analyze a sample of 18 Supercompact Ultraviolet Luminous Galaxies observed with the OSIRIS spectrograph at the Keck Telescope, targeting their Pa-alpha emission. These galaxies, although at z~0.1-0.2, share many similar properties with star-forming galaxies at cosmic noon. We find a total of 84 star-forming clumps with typical sizes of a few hundred parsecs. The star-forming clumps exhibit low values of velocity shear (~12 km/s) and high velocity dispersion (~70 km/s). The dynamical masses of the clumps are typically higher than gas masses inferred from the measured star-formation rates of each clump. We also artificially redshift our data to emulate observations at z=2.2 and allow for a direct comparison with other galaxies at higher redshift. Our results indicate that, due to the effects of clump clustering and low-resolution observations, high-z clumps appear larger at greater cosmological distances. This underscores the importance of using low-redshift observations to anchor studies at earlier epochs. Finally, our results support the idea of growing clump sizes in star-forming galaxies as a function of redshift, although not to scales of kpc as found by other works without the benefits of adaptive optics or gravitational lensing.