JADES NIRSpec Spectroscopy of GN-z11: Lyman-<i>α</i> emission and possible enhanced nitrogen abundance in a <i>z</i> = 10.60 luminous galaxy

Journal article

We present JADES JWST/NIRSpec spectroscopy of GN-z11, the most luminous candidate z>10 Lyman break galaxy in the GOODS-North field with MUV =-21.5. We derive a redshift of z = 10.603 (lower than previous determinations) based on multiple emission lines in our low and medium resolution spectra over 0.7- 5.3 μm. We significantly detect the continuum and measure a blue rest-UV spectral slope of β =-2.4. Remarkably, we see spatially extended Lyman-α in emission (despite the highly neutral intergalactic medium expected at this early epoch), offset 555 km s-1 redwards of the systemic redshift. From our measurements of collisionally excited lines of both low and high ionisation (including [O II] λ3727, [Ne III] λ3869, and C III] λ1909), we infer a high ionisation parameter (log U ∼-2). We detect the rarely seen N IV] λ1486 and N III] λ1748 lines in both our low and medium resolution spectra, with other high ionisation lines seen in the low resolution spectrum, such as He II (blended with O III]) and C IV (with a possible P-Cygni profile). Based on the observed rest-UV line ratios, we cannot conclusively rule out photoionisation from an active galactic nucleus (AGN), although the high C III]/He II and N III]/He II ratios are compatible with a star formation explanation. If the observed emission lines are powered by star formation, then the strong N III] λ1748 observed may imply an unusually high N/O abundance. Balmer emission lines (Hγ, Hδ) are also detected, and if powered by star formation rather than an AGN, we infer a star formation rate of ∼20-30 M⊙ yr-1 (depending on the initial mass function) and low dust attenuation. Our NIRSpec spectroscopy confirms that GN-z11 is a remarkable galaxy with extreme properties seen 430 Myr after the Big Bang

Authors: Bunker, AJ; Saxena, A; Cameron, AJ; Willott, CJ; Curtis-Lake, E

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: EDP Sciences
• Journal: Astronomy & Astrophysics
• Volume: 677
• Pages: A88-A88
• Publication date: 2023-07-12
• Acceptance date: 2023-05-16
• DOI: 10.1051/0004-6361/202346159
• EISSN: 1432-0746
• ISSN: 0004-6361
• Language: English
• Keywords: Doubly ionized oxygen; Redshift; Spectroscopy; Emission spectrum; Galaxy; Active galactic nucleus; Balmer series; Astrophysics; Spectral line; Astronomy; Physics