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

## Abstract

GN-z11 was photometrically selected as a luminous star-forming galaxy candidate at redshift z > 10 on the basis of Hubble Space Telescope imaging data1. Follow-up Hubble Space Telescope near-infrared grism observations detected a continuum break that was explained as the Lyα 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] λ1907, C iii] λ1909 doublet and O iii] λ1666 at z = 10.957 ± 0.001 (when the Universe was only ~420 Myr old, or ~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.

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## Data availability

The Keck MOSFIRE data of this work are publicly available from the Keck Observatory Archive (https://www2.keck.hawaii.edu/koa/public/koa.php). Source data are provided with this paper. Other data of this study are available from the corresponding authors upon reasonable request.

## Code availability

The Keck MOSFIRE data were reduced using a publicly available data reduction pipeline (https://github.com/Keck-DataReductionPipelines/MosfireDRP).

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## Acknowledgements

We acknowledge support from the National Science Foundation of China (11721303, 11890693, 11991052), the National Key R&D Program of China (2016YFA0400702, 2016YFA0400703) and the Chinese Academy of Sciences (CAS) through a China–Chile Joint Research Fund (1503) administered by the CAS South America Center for Astronomy. N.K. acknowledges support from JSPS grant 15H03645. We thank P. Oesch and C. Steidel for discussions on observations and data reduction. We thank A. Feltre, K. Nakajima and T. Nanayakkara for providing data shown in Fig. 3. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The observatory was made possible by the financial support of the W. M. Keck Foundation. We wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

## Author information

Authors

### Contributions

L.J. designed the programme, carried out the Keck observations, analysed the data and prepared the manuscript. N.K. designed the programme and carried out the observations. S.W. and G.W. reduced the images. L.C.H. helped to prepare the manuscript. K.I. and Y.L. assisted with the observations. All authors helped with the scientific interpretations and commented on the manuscript.

### Corresponding authors

Correspondence to Linhua Jiang or Nobunari Kashikawa.

## Ethics declarations

### Competing interests

The authors declare no competing interests.

Peer review information Nature Astronomy thanks Fergus Cullen, Norbert Pirzkal and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

## Extended data

### Extended Data Fig. 1 Detection of the [C III] and C III] emission lines from the first half of the K-band data.

Detection of the [C III] λ1907 and C III] λ1909 emission lines. Same as Fig. 2, but for the first half of the K-band data.

### Extended Data Fig. 2 Detection of the [C III] and C III] emission lines from the second half of the K-band data.

Detection of the [C III] λ1907 and C III] λ1909 emission lines. Same as Fig. 2, but for the second half of the K-band data.

### Extended Data Fig. 3 Detection of the O III] emission line.

Detection of the O III] λ1666 emission line. a, Part of the K-band 2D spectrum with the line (enclosed by the yellow circle) detected at 3.3σ significance. The two negative signals enclosed by the blue circles are the same pattern shown in Fig. 2. b, A smoothed version of the 2D spectrum to better illustrate the line detection; a Gaussian filter with a size of 2.5 pixels is used. c, Extracted 1D spectrum. The grey area represents the 1σ uncertainty region. The hatched areas indicate regions affected by OH skylines. The emission line is shown in green, with the vermillion solid profile being the best-fit Gaussian. d, Same as (c), but from the smoothed 2D spectrum (b).

### Extended Data Fig. 4 SED modelling of GN-z11.

SED modelling of GN-z11. a, SED modelling result using a fixed redshift z = 3.558, that is, the emission line at 22823 Å is assumed to be [O III] λ5007. The red points with 1σ error bars are the observed photometric data points. The downward arrows indicate the 2σ detection upper limits. The horizontal errors indicate the wavelength ranges of the filters. The light blue spectrum represents the best model. The dark blue crosses represent the photometric points predicted by the model. They are inconsistent with the observed values. For comparison, the grey spectrum represents the best model using a fixed redshift z = 10.957. The model photometry (black crosses) is well consistent with the observed photometry. b, Same as (a), but for a fixed redshift z = 5.124, that is, the emission line at 22823 Å is assumed to be [O II] λ3727. The best model is also inconsistent with the observed photometry.

## Source data

### Source Data Fig. 1

Source data for Fig. 1.

### Source Data Fig. 2

Source data for Fig. 2.

## Rights and permissions

Reprints and Permissions

Jiang, L., Kashikawa, N., Wang, S. et al. Evidence for GN-z11 as a luminous galaxy at redshift 10.957. Nat Astron 5, 256–261 (2021). https://doi.org/10.1038/s41550-020-01275-y

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