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We present the algorithm and main results of our semi-numerical simulation, islandFAST, which is developed from the 21cmFAST and designed for the late stage of reionization. The islandFAST predicts the evolution and size distribution of the…

Cosmology and Nongalactic Astrophysics · Physics 2017-08-09 Yidong Xu , Bin Yue , Xuelei Chen

We explore the impact of incorporating physically motivated ionisation and recombination rates on the history and topology of cosmic reionisation, by incorporating inputs from small-volume hydrodynamic simulations into a semi-numerical…

Cosmology and Nongalactic Astrophysics · Physics 2016-02-08 Sultan Hassan , Romeel Davé , Kristian Finlator , Mario G. Santos

The large-scale structure of the ionization field during the epoch of reionization (EoR) can be modeled by the excursion set theory. While the growth of ionized regions during the early stage are described by the "bubble model", the…

Cosmology and Nongalactic Astrophysics · Physics 2018-08-22 Yidong Xu , Bin Yue , Xuelei Chen

During the epoch of reionization (EoR), the first generation of luminous sources in our Universe emitted ionizing photons that almost completely ionized the gas in the intergalactic medium (IGM). The growth of ionized bubbles and the…

Astrophysics of Galaxies · Physics 2025-11-26 Sambit K. Giri , Koki Kakiichi , Michele Bianco , P. Daniel Meerburg

Semi-numeric methods have made it possible to efficiently model the epoch of reionisation (EoR). While most implementations involve a reduction to a simple three-parameter model, we introduce a new mass-dependent ionising efficiency…

Cosmology and Nongalactic Astrophysics · Physics 2018-03-12 Daegene Koh , John H. Wise

We study the evolution of the hydrogen ionization field during the epoch of reionization (EoR) using semi-numerical simulations. By calculating the Minkowski functionals (MFs) of the 21cm brightness temperature field, which provides a…

Cosmology and Nongalactic Astrophysics · Physics 2019-11-14 Zhaoting Chen , Yidong Xu , Yougang Wang , Xuelei Chen

We present the prospects of extracting information about the Epoch of Reionization by identifying the remaining neutral regions, referred to as islands, in tomographic observations of the redshifted 21-cm signal. Using simulated data sets…

Astrophysics of Galaxies · Physics 2019-09-23 Sambit K. Giri , Garrelt Mellema , Thomas Aldheimer , Keri L. Dixon , Ilian T. Iliev

Accuracy in the topology and statistics of a simulated Epoch of Reionization (EoR) are vital to draw connections between observations and physical processes. While full radiative transfer models produce the most accurate reionization…

Cosmology and Nongalactic Astrophysics · Physics 2023-08-09 James E. Davies , Simeon Bird , Simon Mutch , Yueying Ni , Yu Feng , Rupert Croft , Tiziana Di Matteo , J. Stuart B. Wyithe

The reionization process is expected to be prolonged by the small-scale absorbers (SSAs) of ionizing photons, which have been seen as Lyman-limit systems in quasar absorption line observations. We use a set of semi-numerical simulations to…

Cosmology and Nongalactic Astrophysics · Physics 2022-03-09 Peng-Ju Wu , Yidong Xu , Xin Zhang , Xuelei Chen

In a semi-numerical model of reionization, the evolution of ionization fraction is simulated approximately by the ionizing photon to baryon ratio criterion. In this paper we incorporate a semi-analytical model of galaxy formation based on…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 Jie Zhou , Qi Guo , Gaochao Liu , Bin Yue , Yidong Xu , Xuelei Chen

The recent low value of Planck (2016) integrated optical depth to Thomson scattering suggests that the reionization occurred fairly suddenly, disfavoring extended reionization scenarios. This will have a significant impact on the 21cm power…

Cosmology and Nongalactic Astrophysics · Physics 2017-03-27 Sultan Hassan , Romeel Dave , Kristian Finlator , Mario G. Santos

By depleting the ionizing photon budget available to expand cosmic HII regions, recombining systems (or Lyman limit systems) can have a large impact during (and following) cosmic reionization. Unfortunately, directly resolving such…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-18 Emanuele Sobacchi , Andrei Mesinger

We compare the predictions of four different algorithms for the distribution of ionized gas during the Epoch of Reionization. These algorithms are all used to run a 100 Mpc/h simulation of reionization with the same initial conditions. Two…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-18 Oliver Zahn , Andrei Mesinger , Matthew McQuinn , Hy Trac , Renyue Cen , Lars E. Hernquist

Most astrophysical plasmas entail a balance between ionization and recombination. We present new results from the powerful R-matrix method which yields in an ab initio manner: (I) self-consistent photoionization and recombination cross…

Astrophysics · Physics 2007-05-23 Sultana N. Nahar

We present an efficient method to generate large simulations of the Epoch of Reionization (EoR) without the need for a full 3-dimensional radiative transfer code. Large dark-matter-only simulations are post-processed to produce maps of the…

The 21cm signal of neutral hydrogen contains a wealth of information about the poorly constrained era of cosmological history, the Epoch of Reionization (EoR). Recently, AI models trained on EoR simulations have gained significant attention…

Cosmology and Nongalactic Astrophysics · Physics 2026-05-08 Jasper Solt , Jonathan C. Pober , Stephen H. Bach

In recent years there has been considerable progress in our understanding of the nature and properties of the reionization process. In particular, the numerical simulations of this epoch have made a qualitative leap forward, reaching…

The first generation of redshifted 21 cm detection experiments, carried out with arrays like LOFAR, MWA and GMRT, will have a very low signal-to-noise ratio per resolution element (\sim 0.2). In addition, whereas the variance of the…

We have used semi-numerical simulations of reionization to study the behaviour of the power spectrum of the EoR 21-cm signal in redshift space. We have considered two models of reionization, one which has homogeneous recombination (HR) and…

Cosmology and Nongalactic Astrophysics · Physics 2013-09-05 Suman Majumdar , Somnath Bharadwaj , T. Roy Choudhury

In this paper we investigate the nature and distribution of large neutral regions during the late epoch of reionization. In the "bubble model" of reionization, the mass distribution of large ionized regions ("bubbles") during the early…

Cosmology and Nongalactic Astrophysics · Physics 2014-01-17 Yidong Xu , Bin Yue , Meng Su , Zuhui Fan , Xuelei Chen
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