Metal-poor star formation at z > 6 with JWST: new insight into hard radiation fields and nitrogen enrichment on 20 pc scales

ABSTRACT Nearly a decade ago, we began to see indications that reionization-era galaxies power hard radiation fields rarely seen at lower redshift. Most striking were detections of nebular C iv emission in what appeared to be typical low-mass galaxies, requiring an ample supply of 48 eV photons to triply ionize carbon. We have obtained deep JWST/NIRSpec R = 1000 spectroscopy of the two z > 6 C iv-emitting galaxies known prior to JWST. Here, we present a rest-UV to optical spectrum of one of these two systems, the multiply-imaged z = 6.1 lensed galaxy RXCJ2248-ID. NIRCam imaging reveals two compact (<22 pc) clumps separated by 220 pc, with one comprising a dense concentration of massive stars…

• NS
  National Science Foundation

  Awards: 2109066, AST-2109066, 2020750
• NA
  National Aeronautics and Space Administration

  Awards: 5-03127, 80NSSC23K0467, NAS 5-03127
• ST
  Space Telescope Science Institute

  Awards: 5-03127, NAS 5-03127
• US
  United States-Israel Binational Science Foundation

  Awards: 2109066, 2020750
• NS
  Nuclear Safety and Security Commission
• IS
  Israel Science Foundation

  Award: 864/23
• SA
  Science and Technology Facilities Council

  Awards: ST/V00087X/1, ST/S004831/1