Low-redshift Analogs 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 α 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 ^−1 ) and high velocity dispersion (∼70 km s ^−1 ). The dynamical masses of the clumps are typically higher than the gas masses inferred from the measured star formation rate 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 the scales of kiloparsecs as found by other works without the benefits of adaptive optics or gravitational lensing.

Keywords

• Star forming regions
• High-redshift galaxies
• Starburst galaxies
• Galaxies
• Lyman-break galaxies