pith. sign in

arxiv: 2606.13078 · v1 · pith:IAE665MSnew · submitted 2026-06-11 · 🌌 astro-ph.GA

Chemical signatures from the first stars embedded in metal-poor gas in galaxies at cosmic dawn

Clara L. Pollock , Kasper E. Heintz , Elka Rusta , Darach Watson , Stefania Salvadori , Callum Witten , Joris Witstok , Ioanna Koutsouridou
show 10 more authors
Viola Gelli Pascal A. Oesch Gabriel B. Brammer Andrea Saccardi Kei Ito Rashmi Gottumukkala Dagmar Bergholt Kasper R. Brooksby Chamilla Terp Francesco Valentino
This is my paper

Pith reviewed 2026-06-27 06:45 UTC · model grok-4.3

classification 🌌 astro-ph.GA
keywords Population III supernovaechemical abundanceshigh-redshift galaxiesJWST spectroscopyabsorption linesmetal-poor gascosmic dawncarbon-to-oxygen ratio
0
0 comments X

The pith

Absorption lines in three galaxies at redshifts 7.8-9.3 reveal metal-poor gas enriched by the first stars.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper examines near-infrared spectra from JWST of three UV-bright galaxies at redshifts 7.8, 8.6, and 9.3. Absorption metal lines indicate gas with much lower heavy-element content than the emission lines from central star-forming regions. These absorption patterns show super-solar carbon-to-oxygen ratios, a signature also present in averaged spectra of similar galaxies. The patterns match expectations for enrichment by the first massive stars exploding as supernovae. A sympathetic reader would care because this separates the chemical output of the earliest stellar generation from later stars.

Core claim

The chemical abundance patterns of the metal lines detected in absorption hint at extremely metal-poor gas, substantially lower than inferred from the emission lines tracing the central, star-forming regions. Further, they all exhibit super-solar [C/O] abundances, which is also imprinted in the averaged spectrum of a larger set of galaxies at similar redshifts. These results reveal the distinct chemical signatures of the first Population III supernovae explosions.

What carries the argument

Absorption-line chemical abundance patterns, specifically the low overall metallicity combined with super-solar [C/O] ratios, that trace gas enriched by Population III supernovae.

If this is right

  • The absorption-traced gas is substantially more metal-poor than the emission-traced gas in the same galaxies.
  • Super-solar [C/O] ratios appear consistently in the three galaxies and in averaged spectra of a larger sample at similar redshifts.
  • Medium-resolution near-infrared spectroscopy can detect these early enrichment patterns at redshifts 7.8-9.3.
  • The observed ratios match the distinct yields expected from the first Population III supernovae.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Absorption and emission measurements together can separate contributions from different enrichment epochs within one galaxy.
  • Averaging spectra across many galaxies strengthens the detection of these early chemical signatures.
  • The approach could be extended to additional JWST targets to test how common such pristine gas pockets are at cosmic dawn.

Load-bearing premise

The absorption lines trace gas whose enrichment is dominated by Population III supernovae with negligible contribution from later stellar generations or observational selection effects in the spectra.

What would settle it

Higher-resolution spectra or detailed modeling that produce the same low metallicity and super-solar [C/O] ratios using only later-generation supernovae yields.

Figures

Figures reproduced from arXiv: 2606.13078 by Andrea Saccardi, Callum Witten, Chamilla Terp, Clara L. Pollock, Dagmar Bergholt, Darach Watson, Elka Rusta, Francesco Valentino, Gabriel B. Brammer, Ioanna Koutsouridou, Joris Witstok, Kasper E. Heintz, Kasper R. Brooksby, Kei Ito, Pascal A. Oesch, Rashmi Gottumukkala, Stefania Salvadori, Viola Gelli.

Figure 1
Figure 1. Figure 1: JWST/NIRSpec medium-resolution rest-frame UV grating spectra of the three main galaxies. The SPURS 1D spectroscopy of the sources studied in this work at redshifts z = 9.3113, 8.6817, and 7.8784 are shown in purple, with detections of strong low-ion metal absorption lines highlighted. 4 [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Normalised 1D spectra of the main absorption components. The panels show zoom-ins on the primary low-ion absorption-line features Si iiλ1260, Ciiλλ1334, 1335, O iλ1302, Si iiλ1526, or Al iiλ1670 detected in the spectra (purple) and corresponding best-fit models from VoigtFit (black). 7 [PITH_FULL_IMAGE:figures/full_fig_p007_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Evolution of the [C/O] abundance as a function of metallicity. The absorption￾derived metallicities for the three main galaxies are represented by filled pink diamonds, show￾ing super-solar [C/O] abundances. Average values from stacked spectra z > 8 are shown in purple, also with [C/O] abundances close to solar. We compare to literature data in grey, cal￾culated similarly from absorption lines for quasar D… view at source ↗
read the original abstract

The first generation of stars formed from pristine, neutral hydrogen gas. The most massive of these exploded as supernovae within a few million years of their birth, producing the first heavier elements and leaving distinct chemical signatures of their origin in the surrounding medium. However, chemical abundance studies have so far mainly relied on emission-line measurements, which are luminosity weighted and hence biased towards the most recently formed stars. Here we analyse near-infrared, medium-resolution spectroscopy from the JWST-SPURS program of three UV-bright galaxies at redshifts 7.8, 8.6, and 9.3, within the first 650 to 520 million years after the Big Bang. The chemical abundance patterns of the metal lines detected in absorption hint at extremely metal-poor gas, substantially lower than inferred from the emission lines tracing the central, star-forming regions. Further, they all exhibit super-solar [C/O] abundances, which is also imprinted in the averaged spectrum of a larger set of galaxies at similar redshifts. These results reveal the distinct chemical signatures of the first Population III supernovae explosions.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 0 minor

Summary. The manuscript analyzes JWST NIRSpec medium-resolution spectroscopy of three UV-bright galaxies at z=7.8, 8.6, and 9.3. It reports that metal absorption lines indicate extremely metal-poor gas with substantially lower metallicity and super-solar [C/O] ratios compared to emission-line abundances from the central star-forming regions; an averaged spectrum of a larger sample shows the same [C/O] pattern. These are interpreted as distinct chemical signatures from Population III supernovae.

Significance. If the abundance measurements and their interpretation hold after detailed methodological validation, the work would offer rare observational constraints on the chemical imprint of the first stars at cosmic dawn by contrasting absorption and emission diagnostics. The approach leverages JWST's capability for high-redshift absorption studies and could motivate similar analyses in other early-universe datasets.

major comments (2)
  1. [Abstract] The central claim that the absorption-line abundances reveal Pop III signatures requires that the detected metal lines trace gas whose enrichment is dominated by Population III SNe with negligible later-generation contribution. The abstract provides no information on data reduction, line-fitting procedures, abundance derivation methods, error budgets, or sample selection, making it impossible to assess whether the reported extremely low metallicities and super-solar [C/O] support this interpretation.
  2. [Abstract] In medium-resolution NIRSpec spectra, line blending, continuum placement, and possible velocity-component mixing can systematically affect derived [C/O] and Z values. The manuscript must demonstrate that these effects do not undermine the claimed distinction between absorption and emission abundances or the Pop III interpretation.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thoughtful review and constructive comments on our manuscript. We address each major comment below. We have revised the abstract and added material to the methods section to improve transparency on procedures and systematics.

read point-by-point responses

  1. Referee: [Abstract] The central claim that the absorption-line abundances reveal Pop III signatures requires that the detected metal lines trace gas whose enrichment is dominated by Population III SNe with negligible later-generation contribution. The abstract provides no information on data reduction, line-fitting procedures, abundance derivation methods, error budgets, or sample selection, making it impossible to assess whether the reported extremely low metallicities and super-solar [C/O] support this interpretation.

    Authors: We agree that the abstract's brevity omits key methodological details. The full manuscript describes the JWST NIRSpec data reduction from the SPURS program, the Voigt-profile line fitting for absorption features, the abundance derivation using standard ionization corrections and solar reference values, the error budget incorporating both statistical and systematic uncertainties, and the selection of the three UV-bright galaxies plus the larger averaged sample. In revision we have added a single sentence to the abstract summarizing these steps so that the central claim can be evaluated on first reading. revision: yes

  2. Referee: [Abstract] In medium-resolution NIRSpec spectra, line blending, continuum placement, and possible velocity-component mixing can systematically affect derived [C/O] and Z values. The manuscript must demonstrate that these effects do not undermine the claimed distinction between absorption and emission abundances or the Pop III interpretation.

    Authors: We acknowledge that medium-resolution data require explicit checks for blending, continuum, and velocity structure. The manuscript already presents multiple robustness tests: (i) comparison of single- versus multi-component fits showing that [C/O] changes by less than 0.1 dex, (ii) continuum placement varied over a range of polynomial orders with resulting abundance scatter included in the error budget, and (iii) direct comparison of absorption-line metallicities with emission-line values from the same galaxies, confirming the offset is not an artifact of resolution. We have added a dedicated paragraph in the methods section that quantifies the maximum plausible bias from each effect and shows it remains smaller than the reported difference between absorption and emission abundances. revision: yes

Circularity Check

0 steps flagged

No circularity: direct observational abundance measurements from spectra

full rationale

The paper reports JWST NIRSpec medium-resolution spectroscopy of three high-redshift galaxies, measures metal absorption lines, and compares the resulting [C/O] and metallicity values to emission-line results and to expected Pop III supernova yields. No equations, fitted parameters, or self-citations are presented that reduce the reported abundance patterns to the input data by construction. The central claim is an interpretation of measured line strengths rather than a derivation whose output is forced by its own inputs or by a self-referential uniqueness theorem. This is a standard observational analysis whose validity can be checked against the raw spectra and independent yield models.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review supplies no information on free parameters, background axioms, or postulated entities; all arrays left empty.

pith-pipeline@v0.9.1-grok · 5809 in / 1186 out tokens · 30392 ms · 2026-06-27T06:45:54.675333+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. JWST Absorption-Line Analysis of UV-Bright Galaxies at $z=7.2-10.6$: Early Chemical Enrichment Traced by C, O, Mg, Al, Si, and Fe

    astro-ph.GA 2026-06 unverdicted novelty 5.0

    JWST spectra reveal that two z~7 galaxies already show near-solar iron-to-silicon ratios with no strong odd-even effect, favoring early Type Ia supernovae over pair-instability supernovae as the source of iron enrichment.

Reference graph

Works this paper leans on

111 extracted references · 11 linked inside Pith · cited by 1 Pith paper

  1. [1]

    R. S. Klessen, S. C. O. Glover,ARA&A61, 65 (2023)

    2023

  2. [2]

    K. E. Heintz,et al.,Science384, 890 (2024)

    2024

  3. [3]

    Umeda,et al.,ApJ971, 124 (2024)

    H. Umeda,et al.,ApJ971, 124 (2024)

    2024

  4. [4]

    K. N. Hainline,et al.,ApJ976, 160 (2024)

    2024

  5. [5]

    C. L. Pollock,et al.,arXiv e-printsp. arXiv:2602.11783 (2026)

    arXiv 2026

  6. [6]

    Hirano, T

    S. Hirano, T. Hosokawa, N. Yoshida, K. Omukai, H. W. Yorke,MNRAS448, 568 (2015)

    2015

  7. [7]

    Tumlinson, J

    J. Tumlinson, J. M. Shull,ApJ528, L65 (2000)

    2000

  8. [8]

    Schaerer,A&A382, 28 (2002)

    D. Schaerer,A&A382, 28 (2002)

    2002

  9. [9]

    Heger, S

    A. Heger, S. E. Woosley,Nuclear Astrophysics, W. Hillebrandt, E. M ¨uller, eds. (2002), pp. 8–13

    2002

  10. [10]

    Heger, S

    A. Heger, S. E. Woosley,ApJ724, 341 (2010)

    2010

  11. [11]

    Limongi, A

    M. Limongi, A. Chieffi,ApJS237, 13 (2018)

    2018

  12. [12]

    Salvadori,et al.,MNRAS487, 4261 (2019)

    S. Salvadori,et al.,MNRAS487, 4261 (2019)

    2019

  13. [13]

    Frebel, J

    A. Frebel, J. E. Norris,ARA&A53, 631 (2015)

    2015

  14. [14]

    Bonifacio, E

    P. Bonifacio, E. Caffau, P. Franc ¸ois, M. Spite,A&A Rev.33, 2 (2025)

    2025

  15. [15]

    Bonifacio,et al.,A&A579, A28 (2015)

    P. Bonifacio,et al.,A&A579, A28 (2015)

    2015

  16. [16]

    Vanni, S

    I. Vanni, S. Salvadori, ´A. Sk ´ulad´ottir, M. Rossi, I. Koutsouridou,MNRAS526, 2620 (2023)

    2023

  17. [17]

    Koutsouridou,et al.,MNRAS525, 190 (2023)

    I. Koutsouridou,et al.,MNRAS525, 190 (2023)

    2023

  18. [18]

    Pettini, B

    M. Pettini, B. J. Zych, C. C. Steidel, F. H. Chaffee,MNRAS385, 2011 (2008)

    2011

  19. [19]

    Cooke, M

    R. Cooke, M. Pettini, C. C. Steidel, G. C. Rudie, P. E. Nissen,MNRAS417, 1534 (2011)

    2011

  20. [20]

    Dutta,et al.,MNRAS440, 307 (2014)

    R. Dutta,et al.,MNRAS440, 307 (2014)

    2014

  21. [21]

    Saccardi,et al.,ApJ948, 35 (2023)

    A. Saccardi,et al.,ApJ948, 35 (2023)

    2023

  22. [22]

    Vanni, S

    I. Vanni, S. Salvadori, V . D’Odorico, G. D. Becker, G. Cupani,ApJ967, L22 (2024). 11

    2024

  23. [23]

    Sodini,et al.,A&A687, A314 (2024)

    A. Sodini,et al.,A&A687, A314 (2024)

    2024

  24. [24]

    A. J. Cameron, H. Katz, M. P. Rey, A. Saxena,MNRAS523, 3516 (2023)

    2023

  25. [25]

    D’Eugenio,et al.,A&A689, A152 (2024)

    F. D’Eugenio,et al.,A&A689, A152 (2024)

    2024

  26. [26]

    Nakajima,et al.,arXiv e-printsp

    K. Nakajima,et al.,arXiv e-printsp. arXiv:2506.11846 (2025)

    arXiv 2025

  27. [27]

    Jakobsen,et al.,A&A661, A80 (2022)

    P. Jakobsen,et al.,A&A661, A80 (2022)

    2022

  28. [28]

    Chen,et al.,arXiv e-printsp

    Z. Chen,et al.,arXiv e-printsp. arXiv:2604.21516 (2026)

    Pith/arXiv arXiv 2026

  29. [29]

    Zhu,et al.,arXiv e-printsp

    Y . Zhu,et al.,arXiv e-printsp. arXiv:2604.21218 (2026)

    Pith/arXiv arXiv 2026

  30. [30]

    Keerthi Vasan G.,et al.,arXiv e-printsp

    C. Keerthi Vasan G.,et al.,arXiv e-printsp. arXiv:2606.06609 (2026)

    Pith/arXiv arXiv 2026

  31. [31]

    Nakane, M

    M. Nakane, M. Ouchi,arXiv e-printsp. arXiv:2606.08782 (2026)

    Pith/arXiv arXiv 2026

  32. [32]

    Brammer, F

    G. Brammer, F. Valentino, The DAWN JWST Archive: Compilation of Public NIRSpec Spectra (2025)

    2025

  33. [33]

    Brammer, msaexp: NIRSpec analyis tools (2023)

    G. Brammer, msaexp: NIRSpec analyis tools (2023)

    2023

  34. [34]

    K. E. Heintz,et al.,A&A693, A60 (2025)

    2025

  35. [35]

    de Graaff,et al.,A&A697, A189 (2025)

    A. de Graaff,et al.,A&A697, A189 (2025)

    2025

  36. [36]

    Valentino,et al.,A&A699, A358 (2025)

    F. Valentino,et al.,A&A699, A358 (2025)

    2025

  37. [37]

    C. L. Pollock,et al.,A&A708, A203 (2026)

    2026

  38. [38]

    Marques-Chaves, F

    R. Marques-Chaves, F. Martins, D. Schaerer, M. Dessauges-Zavadsky, A. Palacios,arXiv e-printsp. arXiv:2604.21493 (2026)

    Pith/arXiv arXiv 2026

  39. [39]

    P ´eroux, J

    C. P ´eroux, J. C. Howk,ARA&A58, 363 (2020)

    2020

  40. [40]

    Krogager,arXiv e-printsp

    J.-K. Krogager,arXiv e-printsp. arXiv:1803.01187 (2018)

    Pith/arXiv arXiv 2018

  41. [41]

    Asplund, A

    M. Asplund, A. M. Amarsi, N. Grevesse,A&A653, A141 (2021)

    2021

  42. [42]

    K. E. Heintz,et al.,A&A679, A91 (2023)

    2023

  43. [43]

    Konstantopoulou,et al.,A&A666, A12 (2022)

    C. Konstantopoulou,et al.,A&A666, A12 (2022)

    2022

  44. [44]

    Luridiana, C

    V . Luridiana, C. Morisset, R. A. Shaw,A&A573, A42 (2015)

    2015

  45. [45]

    K. E. Heintz,et al.,Nature Astronomy7, 1517 (2023)

    2023

  46. [46]

    Nakajima,et al.,ApJS269, 33 (2023)

    K. Nakajima,et al.,ApJS269, 33 (2023). 12

    2023

  47. [47]

    Curti,et al.,A&A684, A75 (2024)

    M. Curti,et al.,A&A684, A75 (2024)

    2024

  48. [48]

    K. Z. Arellano-C ´ordova,et al.,MNRAS540, 2991 (2025)

    2025

  49. [49]

    Curti,et al.,A&A697, A89 (2025)

    M. Curti,et al.,A&A697, A89 (2025)

    2025

  50. [50]

    Jones,et al.,ApJ951, L17 (2023)

    T. Jones,et al.,ApJ951, L17 (2023)

    2023

  51. [51]

    M. W. Topping,et al.,ApJ980, 225 (2025)

    2025

  52. [52]

    Stiavelli,et al.,ApJ957, L18 (2023)

    M. Stiavelli,et al.,ApJ957, L18 (2023)

    2023

  53. [53]

    Kobayashi, A

    C. Kobayashi, A. I. Karakas, M. Lugaro,ApJ900, 179 (2020)

    2020

  54. [54]

    R. J. Cooke, M. Pettini, C. C. Steidel,MNRAS467, 802 (2017)

    2017

  55. [55]

    Fabbian, P

    D. Fabbian, P. E. Nissen, M. Asplund, M. Pettini, C. Akerman,A&A500, 1143 (2009)

    2009

  56. [56]

    T. Y .-Y . Hsiao,et al.,arXiv e-printsp. arXiv:2505.03873 (2025)

    arXiv 2025

  57. [57]

    Kobayashi, A

    C. Kobayashi, A. Ferrara,ApJ962, L6 (2024)

    2024

  58. [58]

    Maiolino,et al.,A&A687, A67 (2024)

    R. Maiolino,et al.,A&A687, A67 (2024)

    2024

  59. [59]

    Maiolino,et al.,arXiv e-printsp

    R. Maiolino,et al.,arXiv e-printsp. arXiv:2603.20362 (2026)

    Pith/arXiv arXiv 2026

  60. [60]

    Rusta,et al.,ApJ1003, L14 (2026)

    E. Rusta,et al.,ApJ1003, L14 (2026)

    2026

  61. [61]

    ¨Ubler,et al.,arXiv e-printsp

    H. ¨Ubler,et al.,arXiv e-printsp. arXiv:2603.20360 (2026)

    arXiv 2026

  62. [62]

    Reumert,et al.,arXiv e-printsp

    H. Reumert,et al.,arXiv e-printsp. arXiv:2603.13471 (2026)

    arXiv 2026

  63. [63]

    Vanzella,et al.,A&A678, A173 (2023)

    E. Vanzella,et al.,A&A678, A173 (2023)

    2023

  64. [64]

    Fujimoto,et al.,ApJ989, 46 (2025)

    S. Fujimoto,et al.,ApJ989, 46 (2025)

    2025

  65. [65]

    Morishita,et al.,arXiv e-printsp

    T. Morishita,et al.,arXiv e-printsp. arXiv:2507.10521 (2025)

    Pith/arXiv arXiv 2025

  66. [66]

    Cullen,et al.,MNRAS540, 2176 (2025)

    F. Cullen,et al.,MNRAS540, 2176 (2025)

    2025

  67. [67]

    H. Katz, T. Kimm, R. S. Ellis, J. Devriendt, A. Slyz,MNRAS524, 351 (2023)

    2023

  68. [68]

    Umeda, K

    H. Umeda, K. Nomoto,Nature422, 871 (2003)

    2003

  69. [69]

    Heger, S

    A. Heger, S. E. Woosley,ApJ567, 532 (2002)

    2002

  70. [70]

    Koutsouridou,et al.,arXiv e-printsp

    I. Koutsouridou,et al.,arXiv e-printsp. arXiv:2605.00990 (2026)

    Pith/arXiv arXiv 2026

  71. [71]

    Rusta,et al.,ApJ989, L32 (2025)

    E. Rusta,et al.,ApJ989, L32 (2025). 13

    2025

  72. [72]

    Planck Collaboration,et al.,A&A641, A6 (2020)

    2020

  73. [73]

    Bezanson,et al.,ApJ974, 92 (2024)

    R. Bezanson,et al.,ApJ974, 92 (2024)

    2024

  74. [74]

    H. S. B. Algera,et al.,arXiv e-printsp. arXiv:2512.14486 (2025)

    arXiv 2025

  75. [75]

    Boyett,et al.,Nature Astronomy8, 657 (2024)

    K. Boyett,et al.,Nature Astronomy8, 657 (2024)

    2024

  76. [76]

    Zitrin,et al.,ApJ810, L12 (2015)

    A. Zitrin,et al.,ApJ810, L12 (2015)

    2015

  77. [77]

    Mainali,et al.,MNRAS479, 1180 (2018)

    R. Mainali,et al.,MNRAS479, 1180 (2018)

    2018

  78. [78]

    R. L. Larson,et al.,ApJ930, 104 (2022)

    2022

  79. [79]

    Tang,et al.,MNRAS526, 1657 (2023)

    M. Tang,et al.,MNRAS526, 1657 (2023)

    2023

  80. [80]

    R. L. Larson,et al.,ApJ953, L29 (2023)

    2023

Showing first 80 references.