J/A+A/705/A114 Lyman-alpha damping wings in z∼6-13 galaxies (Mason+, 2026)
Constraints on the z∼6-13 intergalactic medium from JWST spectroscopy of
Lyman-alpha damping wings in galaxies.
Mason C.A., Chen Z., Stark D.P., Lu T.-Y., Topping M., Tang M.
<Astron. Astrophys. 705, A114 (2026)>
=2026A&A...705A.114M 2026A&A...705A.114M (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Redshifts ; Photometry, ultraviolet
Keywords: galaxies: high-redshift - cosmology: reionization - IGM
Abstract:
JWST provides a unique dataset for studying the earliest stages of
reionisation at z>9, promising insights into the first galaxies. Many
JWST/NIRSpec prism spectra of z>5 galaxies have revealed smooth
Lyman-alpha breaks, implying damping wing scattering by neutral
hydrogen.
We investigate what current prism spectra imply about the
intergalactic medium (IGM) at z>6 and how best to use NIRSpec spectra
to recover IGM properties. We use a sample of 99 z∼5.5-13 galaxies
with high S/N prism spectra in the public archive, including 12 at
z>10.
We analyse these spectra using damping wing sightlines from
inhomogeneous reionising IGM simulations, mapping between the distance
of a source from the neutral IGM and the average IGM neutral fraction.
We marginalise over absorption by local neutral hydrogen around the
galaxies and Lyman-alpha emission.
We observe a decline in the median and variance of flux around the
Lyα break with increasing redshift, consistent with an
increasingly neutral IGM, as ionized regions become smaller and rarer.
At z≳9 the spectra become consistent with an almost fully neutral
IGM. We find S/N > 15 per pixel is required to robustly estimate IGM
properties from prism spectra. We fit a sub-sample of high S/N spectra
and infer mean IGM neutral fractions of X{bar}HI=0.33-0.27+0.18,
0.64-0.23+0.17 (>0.70 excluding GNz11) at z~=6.5, 9.3. We also
investigate local HI absorption, finding a median column density of
log10NHI~=1020.8cm-2, comparable to z∼3 Lyman-break galaxies, with
no significant redshift evolution z≳5.5. We find galaxies showing the
highest column density absorption are more likely to be in close
associations of sources (≲500pkpc), implying absorption is enhanced
in massive dark matter halos. Future deep prism and grating
spectroscopy of z>9 sources will provide tighter constraints on the
earliest stages of reionisation, key for understanding the onset of
star formation.
Description:
This catalog contains the source list used in our analysis of the
Lyman-alpha damping wings measured in JWST/NIRSpec spectra of galaxies
at z=5.5-13. The table includes identifiers, sky coordinates,
spectroscopic redshifts, and absolute UV magnitudes.
The data were obtained in the CEERS, JADES, and UNCOVER surveys.
Redshifts were measured from rest-optical emission lines or the
Lyman-alpha break. Absolute magnitudes were derived assuming standard
cosmology.
This work is based on observations made with the NASA/ESA/CSA James
Webb Space Telescope. We select our sample from public JWST NIRSpec
data from CEERS (GO-1345, DDT-2750, Finkelstein et al.
2022ApJ...940L..55F 2022ApJ...940L..55F; Arrabal Haro et al. 2023ApJ...951L..22A 2023ApJ...951L..22A), UNCOVER
(GO-2561, Bezanson et al. 2024ApJ...974...92B 2024ApJ...974...92B) and JADES GOODS-S
(GTO-1210, GO-3215, Eisenstein et al. 2023arXiv230602465E 2023arXiv230602465E,
2023arXiv231012340E 2023arXiv231012340E).
Reduction of NIRSpec spectra used in this work are described by Tang
et al. (2023MNRAS.526.1657T 2023MNRAS.526.1657T, 2024ApJ...975..208T 2024ApJ...975..208T); Chen et al.
(2024MNRAS.528.7052C 2024MNRAS.528.7052C) using the JWST data reduction pipeline.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablef1.dat 69 99 Source catalog
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Byte-by-byte Description of file: tablef1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- ID Source identifier
21- 31 F11.7 deg RAdeg Right Ascension (J2000)
33- 43 F11.7 deg DEdeg Declination (J2000)
45- 50 F6.3 --- zsp Spectroscopic redshift
52- 57 F6.2 mag UVMAG Absolute UV magnitude, corrected for magnification
59- 62 F4.2 mag e_UVMAG Lower uncertainty on MUV (1σ)
64- 67 F4.2 mag E_UVMAG Upper uncertainty on MUV (1σ)
69 I1 --- Flag [1/2]? Optional flag (1)
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Note (1): Optional flag as follows:
1 = SNR>15 subset
2 = Lyman-break-only redshifts subset
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Acknowledgements:
Charlotte Mason, charlotte.mason(at)nbi.ku.dk
(End) Patricia Vannier [CDS] 17-Nov-2025