RELICS: Small-scale Star Formation in Lensed Galaxies at z=6-10

Detailed observations of star-forming galaxies at high redshift are critical to understanding the formation and evolution of the earliest galaxies. Gravitational lensing provides an important boost, allowing observations at physical scales unreachable in unlensed galaxies. We present three lensed galaxies from the RELICS survey at z (phot) = 6-10, including the most highly magnified galaxy at z (phot) similar to 6 (WHL 0137-zD1, dubbed the Sunrise Arc), the brightest known lensed galaxy at z (phot) similar to 6 (MACS 0308-zD1), and the only spatially resolved galaxy currently known at z (phot) similar to 10 (SPT 0615-JD). The Sunrise Arc contains seven star-forming clumps with delensed radii as small as 3 pc, the smallest spatial scales yet observed in a z > 6 galaxy, while SPT 0615-JD contains features measuring a few tens of parsecs. MACS 0308-zD1 contains an r similar to 30 pc clump with a star formation rate (SFR) of similar to 3 M (circle dot) yr(-1), giving it an SFR surface density of sigma(SFR) similar to 10(3) M (circle dot) yr(-1) kpc(-2). These galaxies provide a unique window into small-scale star formation during the epoch of reionization. They will be excellent targets for future observations with JWST, including one approved program targeting the Sunrise Arc.

Automated summary

Detailed observations of highly magnified and spatially resolved lensed galaxies at high redshift provide valuable insights into the formation and evolution of early galaxies. Three lensed galaxies at z=6-10, including the Sunrise Arc (WHL 0137-zD1), MACS 0308-zD1, and SPT 0615-JD, offer unique opportunities to study star formation at small spatial scales during the epoch of reionization. These galaxies exhibit unprecedented features, such as 3 pc star-forming clumps and a star formation rate surface density of 10(3) M (circle dot) yr(-1) kpc(-2). Future observations with JWST, including a program targeting the Sunrise Arc, will further enhance our understanding of the earliest galaxies.