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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…

Instrumentation and Methods for Astrophysics · Physics 2026-01-01 Cody Carr , Renyue Cen , Brian Fleming , Sophia Flury , Stephan McCandliss , Sally Oey , Allison Strom

The fraction of ionizing photons escaping from galaxies, $f_{esc}$, is at the same time a crucial parameter in modelling reionization and a very poorly known quantity, especially at high redshift. Recent observations are starting to…

The fraction of ionizing photons that escape from young star-forming galaxies is one of the largest uncertainties in determining the role of galaxies in cosmic reionization. Yet traditional techniques for measuring this fraction are…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-15 Tucker Jones , Richard S. Ellis , Matthew A. Schenker , Daniel P. Stark

We calculate the hydrogen and helium-ionizing radiation escaping star-forming molecular clouds, as a function of the star cluster mass and compactness, using a set of high-resolution radiation-magneto-hydrodynamic simulations of star…

Astrophysics of Galaxies · Physics 2020-01-29 Chong-Chong He , Massimo Ricotti , Sam Geen

We study the reionization of the Universe due to haloes that host galaxies undergoing bursts of star formation. By comparing the recent results from the James Webb Space Telescope (JWST) with the cosmological hydrodynamical simulation EAGLE…

Astrophysics of Galaxies · Physics 2026-05-06 Nachiket Joshi , Mahavir Sharma

A thorough analysis of well studied giant HII regions on galactic discs for which we know the ionizing stellar population, the gas metallicity and the Wolf-Rayet population, leads to photoionization models which can only match all observed…

Astrophysics · Physics 2007-05-23 M. Castellanos , A. I. Diaz , G. Tenorio-Tagle

In this work we investigate the properties of the sources that reionized the intergalactic medium (IGM) in the high-redshift Universe. Using a semi-analytical model aimed at reproducing galaxies and black holes in the first 1.5 Gyr of the…

Using our cosmological radiative transfer code, we study the implications of the updated QSO emissivity and star formation history for the escape fraction (f_esc) of hydrogen ionizing photons from galaxies. We estimate the f_esc that is…

Cosmology and Nongalactic Astrophysics · Physics 2016-09-13 Vikram Khaire , Raghunathan Srianand , Tirthankar Roy Choudhury , Prakash Gaikwad

We use a large sample of galaxies at z~3 to establish a relationship between reddening, neutral gas covering fraction (fcov(HI)), and the escape of ionizing photons at high redshift. Our sample includes 933 galaxies at z~3, 121 of which…

Astrophysics of Galaxies · Physics 2016-09-21 Naveen A. Reddy , Charles C. Steidel , Max Pettini , Milan Bogosavljevic , Alice Shapley

We study the observed cosmic ionizing background as a constraint on the nature of the sources responsible for the reionization of the Universe. In earlier work, we showed that extrapolations of the Ultra-Violet Luminosity Function (LF) of…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-18 Fabio Fontanot , Stefano Cristiani , Christoph Pfrommer , Guido Cupani , Eros Vanzella

Recent observations show that the measured rates of star formation in the early universe are insufficient to produce re-ionization, and therefore, another source of ionizing photons is required. In this \emph{Letter}, we examine the…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Michael A. Dopita , Lawrence M. Krauss , Ralph S. Sutherland , Chiaki Kobayashi , Charles H. Lineweaver

Star-forming galaxies in the early universe provide us with perhaps the most natural way of explaining the reionization of the universe. Current observational results are sufficiently comprehensive, as to allow us to approximately calculate…

Astrophysics of Galaxies · Physics 2016-01-27 Rychard J. Bouwens

The protagonists of cosmic reionization remain elusive. Faint star-forming galaxies are leading candidates because they are numerous and may have significant ionizing photon escape fractions ($f_{esc}$). Here we update this picture via an…

Astrophysics of Galaxies · Physics 2020-04-07 Rohan P. Naidu , Sandro Tacchella , Charlotte A. Mason , Sownak Bose , Pascal A. Oesch , Charlie Conroy

The cosmic ultraviolet (UV) ionizing background impacts the formation of dwarf galaxies in the low-redshift universe (z=3) by suppressing gas infall into galactic halos with circular velocities up to v(circ)=75 km/s. Using a…

Astrophysics · Physics 2008-11-26 Mark Dijkstra , Zoltan Haiman , Martin J. Rees , David H. Weinberg

The escape fraction of Lyman continuum photons (fesc(LyC)) is the last key unknown in our understanding of cosmic reionization. Directly estimating the escape fraction (fesc) of ionizing photons in the epoch of reionization (EoR) is…

The end of the Cosmic Dark Age marked the onset of reionization, driven by extreme-UV photons from the first galaxies. Direct detection of such photons has remained challenging due to strong intergalactic attenuation. Here, we report the…

In this paper, we address which sources contributed most of the reionizing photons. Our argument assumes that the reionization ended around z ~ 6 and that it was a relatively quick process, i.e., that there was a non-negligible fraction of…

Astrophysics · Physics 2009-11-10 Haojing Yan , Rogier A. Windhorst

One of the most crucial yet poorly constrained parameters in modelling the ionizing emissivity is the escape fraction of photons from star-forming galaxies. Several theoretical and observational studies have been conducted over the past few…

Cosmology and Nongalactic Astrophysics · Physics 2023-05-24 Sourav Mitra , Atrideb Chatterjee

High-resolution numerical simulations including feedback and aimed at calculating the escape fraction (fesc) of hydrogen-ionizing photons often assume stellar radiation based on single-stellar population synthesis models. However, strong…

Astrophysics of Galaxies · Physics 2020-09-30 Amy Secunda , Renyue Cen , Taysun Kimm , Ylva Gotberg , Selma E. de Mink

Newly formed stars have a profound impact on their environment by depositing energy and momentum into the surrounding gas. However, only a fraction of the stellar feedback is retained in the cloud and observational constraints are needed to…