S. Vejlgaard

University of Copenhagen

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P. Jakobsson

University of Iceland

K. E. Heintz

DAWN Center for Independent Living

N. R. Tanvir

University of Leicester

D. Watson

University of Copenhagen

Meghana Killi

University of Copenhagen

Abdurrouf

University of Brawijaya

Rohan P. Naidu

Kavli Institute for Particle Astrophysics and Cosmology

K. Wiersema

University of Washington

R. Salvaterra

Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano

M. de Pasquale

University of Messina

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University of Copenhagen

Kennedy Center

DAWN Center for Independent Living

National Institute for Astrophysics

Brera Astronomical Observatory

Technical University of Denmark

Space Telescope Science Institute

Centre National de la Recherche Scientifique

Center for Astrophysics Harvard & Smithsonian

Max Planck Institute for Astronomy

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Neutral fraction of hydrogen in the intergalactic medium surrounding high-redshift Gamma-Ray Burst 210905A

Monthly Notices of the Royal Astronomical Society (2024)

H. Fausey S. Vejlgaard A. J. van der Horst K. E. Heintz L. Izzo

The Epoch of Reionization (EoR) is a key period of cosmological history in which the intergalactic medium (IGM) underwent a major phase change from being neutral to almost completely ionized. Gamma-ray bursts (GRBs) are luminous and unique probes of their environments that can be used to study the timeline for the progression of the EoR. Here we present a detailed analysis of the ESO Very Large Telescope X-shooter spectrum of GRB 210905A, which resides at a redshift of z ~ 6.3. We focus on estimating the fraction of neutral hydrogen, xHI, on the line of sight to the host galaxy of GRB 210905A by fitting the shape of the Lyman-alpha damping wing of the afterglow spectrum. The X-shooter spectrum has a high signal to noise ratio, but the complex velocity structure of the host galaxy limits the precision of our conclusions. The statistically preferred model suggests a low neutral fraction with an 3-sigma upper limit of xHI < 0.15, indicating that the IGM around the GRB host galaxy is mostly ionized. We discuss complications in current analyses and potential avenues for future studies of the progression of the EoR and its evolution with redshift.

10.1093/mnras/stae2757

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Strong damped Lyman-α absorption in young star-forming galaxies at redshifts 9 to 11

Science (2024)

K. E. Heintz D. Watson Gabriel Brammer S. Vejlgaard Anne Hutter

Primordial neutral atomic gas, mostly composed of hydrogen, is the raw material for star formation in galaxies. However, there are few direct constraints on the amount of neutral atomic hydrogen (H i ) in galaxies at early cosmic times. We analyzed James Webb Space Telescope (JWST) near-infrared spectroscopy of distant galaxies, at redshifts ≳8. From a sample of 12 galaxies, we identified three that show strong damped Lyman-α absorption due to H i in their local surroundings. The galaxies are located at spectroscopic redshifts of 8.8, 10.2, and 11.4, corresponding to 400 to 600 million years after the Big Bang. They have H i column densities ≳10 22 cm −2 , which is an order of magnitude higher than expected for a fully neutral intergalactic medium, and constitute a gas-rich population of young star-forming galaxies.

10.1126/science.adj0343

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