Resolving star formation processes at 10-100s pc resolution in distant galaxies with JWST/NIRCam

Adélaïde Claeyssens – CRAL, Lyon

Distant galaxies present a very irregular morphology dominated by compact stellar sub-structures called “clumps”. The physical properties of these star-forming systems remain relatively unexplored and their role in galaxy formation and evolution is not clear. The first detections of UV-bright clumps from z=10 to z=1 indicate that these star-forming clumps could be a major mode of star formation and galaxy assembly. However, resolving structures at 10-100s pc scales in high redshift galaxies (z>1) is hardly achievable with current telescopes even with space-based observations. Combining the unprecedented sensitivity and spatial resolution of JWST with the natural gravitational lens telescopes is the only way to reach hundred/sub-hundred pc resolutions in hundreds of galaxies, necessary to resolve individual star-forming systems and star clusters at UV-optical wavelengths.

I present the first results on resolved high-redshift stellar structures observed in JWST/NIRCam observations of strongly lensed galaxies from multiple galaxy cluster fields (SMACS0723, WHL0137, Abell2744, AbellS1063). The optical rest-frame, probed with the JWST, enables us to measure physical properties of >2000 clumpy structures (age, mass, extinction). We derive effective radii and stellar mass overlapping with massive star clusters in the local universe. The properties of these compact structures enable us to trace the star formation history with galaxies and study the processes of stellar clumps and star clusters formation and evolution and galactic bulge growth across redshift. These studies show the potential of JWST observations for understanding the conditions under which galaxies assembly and evolve across the cosmic time and allow us to study for the first time the formation and the role of star clusters in rapidly evolving galaxies.