Evidence for GN-z11 as a luminous galaxy at redshift 10.957

GN-z11 was photometrically selected as a luminous star-forming galaxy candidate at redshift z > 10 on the basis of Hubble Space Telescope imaging data(1). Follow-up Hubble Space Telescope near-infrared grism observations detected a continuum break that was explained as the Ly alpha break corresponding to z=11.09(-0.12)(+0.08) (ref.(2)). However, its accurate redshift remained unclear. Here we report a probable detection of three ultraviolet emission lines from GN-z11, which can be interpreted as the [C III] lambda 1907, C III] lambda 1909 doublet and O III] lambda 1666 at z = 10.957 +/- 0.001 (when the Universe was only similar to 420 Myr old, or similar to 3% of its current age). This is consistent with the redshift of the previous grism observations, supporting GN-z11 as the most distant galaxy known to date. Its ultraviolet lines probably originate from dense ionized gas that is rarely seen at low redshifts, and its strong [C III] and C III] emission is partly due to an active galactic nucleus or enhanced carbon abundance. GN-z11 is luminous and young, yet moderately massive, implying a rapid build-up of stellar mass in the past. Future facilities will be able to find the progenitors of such galaxies at higher redshift and probe the cosmic epoch at the beginning of reionization.

Automated summary

GN-z11, the most distant galaxy known to date, shows strong [C III] and C III] emission lines possibly originating from an active galactic nucleus or enhanced carbon abundance, indicating rapid build-up of stellar mass.