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The Epoch of Reionization marks the last major phase transition in the early Universe, during which the majority of neutral hydrogen once filling the intergalactic medium was ionized by the first galaxies. The James Webb Space Telescope is…

Astrophysics of Galaxies · Physics 2025-07-01 Cody Carr , Renyue Cen , Sophia Flury , Sally Oey , Stephan McCandliss , Allison Strom

Measurements of the ionisation state of the intergalactic medium (IGM) can probe the sources of the extragalactic ionising background. We provide new measurements of the ionising emissivity of galaxies using measurements of the ionising…

Astrophysics of Galaxies · Physics 2025-07-04 Christopher Cain , Anson D'Aloisio , Julian B. Munoz

Reionization is thought to have occurred in the redshift range of $6 < z < 9$, which is now being probed by both deep galaxy surveys and CMB observations. Using halo abundance matching over the redshift range $5<z<8$ and assuming smooth,…

Astrophysics of Galaxies · Physics 2016-05-04 Guochao Sun , Steven R. Furlanetto

We present a Bayesian inference on the neutral hydrogen fraction of the intergalactic medium (IGM), $x_{\textrm{HI}}$, at $z \sim$ 6-8 using the properties of Lyman break galaxies during the Epoch of Reionization. We use large samples of…

We compute the escape of ionizing radiation from galaxies in the redshift interval z=4-10, i.e., during and after the epoch of reionization, using a high-resolution set of galaxies, formed in fully cosmological simulations. The simulations…

Cosmology and Nongalactic Astrophysics · Physics 2010-02-02 Alexei O. Razoumov , Jesper Sommer-Larsen

The reionization of the Universe is one of the most important topics of present day astrophysical research. The most plausible candidates for the reionization process are star-forming galaxies, which according to the predictions of the…

The rapid decline in the number of strong Lyman Alpha (Lya) emitting galaxies at z > 6 provides evidence for neutral hydrogen in the IGM, but is difficult to explain with plausible models for reionization. We demonstrate that the observed…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-18 Mark Dijkstra , Stuart Wyithe , Zoltan Haiman , Andrei Mesinger , Laura Pentericci

The escaping ionising efficiency from galaxies, $f_{\rm esc}\xi_{\rm ion}$, is a crucial ingredient for understanding their contribution to hydrogen reionisation, but both of its components, $f_{\rm{esc}}$ and $\xi_{\rm{ion}}$, are…

Astrophysics of Galaxies · Physics 2024-09-16 Sarah E. I. Bosman , Frederick B. Davies

The escape fraction of Lyman-continuum (LyC) photons ($f_{esc}$) is a key parameter for determining the sources of cosmic reionization at $z\geq 6$. At these redshifts, owing to the opacity of the intergalactic medium, the LyC emission…

High redshift star-forming galaxies are likely responsible for the reionization of the Universe, yet direct detection of their escaping ionizing (Lyman continuum) photons has proven to be extremely challenging. In this study, we search for…

We use a large set of hydrodynamical simulations, combined with measurements of the Lyman alpha opacity of the IGM taken from the literature, to obtain robust estimates for the photoionization rate per hydrogen atom at z=5 and 6. We find…

Astrophysics · Physics 2009-11-13 James S. Bolton , Martin G. Haehnelt

Proto-galaxies forming in low-mass dark matter haloes are thought to provide the majority of ionizing photons needed to reionize the Universe, due to their high escape fractions of ionizing photons. We study how the escape fraction in…

Cosmology and Nongalactic Astrophysics · Physics 2015-07-09 Jan-Pieter Paardekooper , Sadegh Khochfar , Claudio Dalla Vecchia

We present the escape fraction of hydrogen ionizing photons (f_esc) from a sample of 34 high-resolution cosmological zoom-in simulations of galaxies at z>5 in the Feedback in Realistic Environments project, post-processed with a Monte Carlo…

We measure escape fractions, $f_{\rm esc}$, of ionizing radiation from galaxies in the SPHINX suite of cosmological radiation-hydrodynamical simulations of reionization, resolving halos with $M_{\rm vir} \gtrapprox 7.5 \times 10^7 \…

We use a three-dimensional radiation transfer code to calculate the steady-state escape fraction of ionizing photons from disk galaxies as a function of redshift and galaxy mass. The gaseous disks are assumed to be isothermal (with a sound…

Astrophysics · Physics 2009-10-31 Kenneth Wood , Abraham Loeb

An estimate for the number of ionizing photons per baryon as a function of redshift is computed based on the plausible extrapolation of the observed galaxy UV luminosity function and the latest results on the properties of the escape…

Astrophysics · Physics 2008-11-26 Nickolay Y. Gnedin

Star-forming galaxies are considered the likeliest source of the H I ionizing Lyman Continuum (LyC) photons that reionized the intergalactic medium at high redshifts. However, above z >~ 6, the neutral intergalactic medium prevents direct…

A population of early star-forming galaxies is the leading candidate for the re-ionization of the universe. It is still unclear what conditions and physical processes would enable a significant fraction of the ionizing photons to escape…

Astrophysics of Galaxies · Physics 2015-09-16 Rachael Alexandroff , Timothy Heckman , Sanchayeeta Borthakur , Roderik Overzier , Claus Leitherer

The rapidly declining population of bright quasars at z~3 appears to make an increasingly small contribution to the ionising background at the HI Lyman limit. It is then generally though that massive stars in (pre-)galactic systems may…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-11 Francesco Haardt , Ruben Salvaterra

Ionizing photons must have escaped from high-redshift galaxies, but the neutral high-redshift intergalactic medium makes it unlikely to directly detect these photons during the Epoch of Reionization. Indirect methods of studying ionizing…

Astrophysics of Galaxies · Physics 2022-08-17 Thomas Seive , John Chisholm , Floriane Leclercq , Gregory Zeimann