A Nitrogen-rich AGN Powering a Large Ionizing Bubble at z = 8.63

Abstract We report the detection of Ly α in CANUCS-LRD-z8.6, a recently discovered active galactic nucleus (AGN) at z = 8.63 by R. Tripodi et al. (2025), in new NIRSpec/MSA G140H/F070LP observations. We detect broad Ly α emission (FWHM = 1540 ± 260 km s −1 ) near the systemic velocity, which suggests a large ionizing bubble, considering that the Universe is almost fully neutral at the redshift. Through Ly α line-shape modeling assuming a Strömgren sphere, we find a large bubble radius, R b = 1 . 5 − 0.2 + 0.3 pMpc, and a moderately high Ly α escape fraction, f esc = 11% ± 3%. The intrinsic line width is inferred to be broad (2200 ± 280 km s −1 ), likely originating in the broad-line region. Existing data indicate that CANUCS-LRD-z8.6 is within a mild overdensity, δ = 1 . 8 − 0.6 + 3.0 , suggesting that other galaxies in its proximity might have contributed to the formation of the bubble. The high N IV ] λ 1488 /C IV λ 1548 and N IV ] λ 1488 /O III ] λ 1661 line ratios measured in existing NIRSpec/PRISM data indicate nitrogen enrichment in this metal-poor, low-luminosity AGN. The spectroscopic features are overall similar to those of other nitrogen-rich galaxies discovered in the literature, such as GN-z11 and GHZ2/GLASSz12. This suggests that CANUCS-LRD-z8.6 may represent one of the evolutionary phases of those nitrogen-rich galaxies.