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We present a method to construct semi-numerical ``simulations'', which can efficiently generate realizations of halo distributions and ionization maps at high redshifts. Our procedure combines an excursion-set approach with first-order…

Astrophysics · Physics 2009-11-13 Andrei Mesinger , Steven Furlanetto

Cosmological neutral hydrogen (HI) surveys provide a promising tomographic probe of the post-reionization era and of the standard model of cosmology. Simulations of this signal are crucial for maximizing the utility of these surveys. We…

Cosmology and Nongalactic Astrophysics · Physics 2025-04-09 Pascal Hitz , Pascale Berner , Devin Crichton , John Hennig , Alexandre Refregier

A very large dynamic range with simultaneous capture of both large- and small-scales in the simulations of cosmic structures is required for correct modelling of many cosmological phenomena, particularly at high redshift. This is not always…

Cosmology and Nongalactic Astrophysics · Physics 2020-04-15 Ainulnabilah Nasirudin , Ilian T. Iliev , Kyungjin Ahn

We present a new hybrid code for large volume, high resolution simulations of cosmic reionization, which utilizes a N-body algorithm for dark matter, physically motivated prescriptions for baryons and star formation, and an adaptive ray…

Astrophysics · Physics 2009-11-11 Hy Trac , Renyue Cen

The evolution of neutral hydrogen (HI) across redshifts is a powerful probe of cosmology, large scale structure in the universe and the intergalactic medium. Using a data-driven halo model to describe the distribution of HI in the…

Cosmology and Nongalactic Astrophysics · Physics 2018-05-22 Hamsa Padmanabhan

In this work we present a new hybrid method to simulate the thermal effects of the reionization in cosmological hydrodynamical simulations. The method improves upon the standard approach used in simulations of the intergalactic medium (IGM)…

Cosmology and Nongalactic Astrophysics · Physics 2019-06-11 Jose Oñorbe , F. B. Davies , Z. Lukić , J. F. Hennawi , D. Sorini

The observed high covering fractions of neutral hydrogen (HI) with column densities above $\sim 10^{17} \rm{cm}^{-2}$ around Lyman-Break Galaxies (LBGs) and bright quasars at redshifts z ~ 2-3 has been identified as a challenge for…

Cosmology and Nongalactic Astrophysics · Physics 2016-02-25 Alireza Rahmati , Joop Schaye , Richard G. Bower , Robert A. Crain , Michelle Furlong , Matthieu Schaller , Tom Theuns

We present results from a large volume simulation of Hydrogen reionization. We combine 3d radiative transfer calculations and an N-body simulation, describing structure formation in the intergalactic medium, to detail the growth of HII…

Upcoming 21cm surveys will map the spatial distribution of cosmic neutral hydrogen (HI) over very large cosmological volumes. In order to maximize the scientific return of these surveys, accurate theoretical predictions are needed.…

Cosmology and Nongalactic Astrophysics · Physics 2021-07-29 Digvijay Wadekar , Francisco Villaescusa-Navarro , Shirley Ho , Laurence Perreault-Levasseur

We use a set of cosmological simulations combined with radiative transfer calculations to investigate the distribution of neutral hydrogen in the post-reionization Universe. We assess the contributions from the metagalactic ionizing…

Cosmology and Nongalactic Astrophysics · Physics 2013-08-27 Alireza Rahmati , Andreas H. Pawlik , Milan Raičević , Joop Schaye

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 distribution of 21 cm emission from neutral hydrogen is a powerful cosmological and astrophysical probe, as it traces the underlying dark matter and cold gas distributions throughout cosmic times. However, the prediction of observable…

Cosmology and Nongalactic Astrophysics · Physics 2026-05-22 Satvik Mishra , Roberto Trotta , Matteo Viel

We model the distribution of neutral Hydrogen (HI hereafter) in the post-reionization universe. This model uses gravity only N-Body simulations and an ansatz to assign HI to dark matter haloes that is consistent with observational…

Cosmology and Nongalactic Astrophysics · Physics 2010-09-02 J. S. Bagla , Nishikanta Khandai , Kanan K. Datta

The structural and dynamic properties of the dark matter halos, though an important ingredient in understanding large-scale structure formation, require more conservative particle resolution than those required by halo mass alone in a…

Cosmology and Nongalactic Astrophysics · Physics 2022-11-23 Sujatha Ramakrishnan , Premvijay Velmani

We describe a combined halo model to constrain the distribution of neutral hydrogen (HI) in the post-reionization universe. We combine constraints from the various probes of HI at different redshifts: the low-redshift 21-cm emission line…

Cosmology and Nongalactic Astrophysics · Physics 2017-08-23 Hamsa Padmanabhan , Alexandre Refregier

Halo models provide a simple and computationally inexpensive way to investigate the connection between galaxies and their dark matter haloes. However, these models rely on the assumption that the role of baryons can be easily parametrized…

Cosmology and Nongalactic Astrophysics · Physics 2020-01-08 Gillian D. Beltz-Mohrmann , Andreas A. Berlind , Adam O. Szewciw

Resolving faint galaxies in large volumes is critical for accurate cosmic reionisation simulations. While less demanding than hydrodynamical simulations, semi-analytic reionisation models still require very large N-body simulations in order…

Astrophysics of Galaxies · Physics 2020-10-28 Yisheng Qiu , Simon J. Mutch , Pascal J. Elahi , Rhys J. J. Poulton , Chris Power , J. Stuart B. Wyithe

We present a comprehensive analysis of atomic hydrogen (HI) properties using a semi-analytical model of galaxy formation and N-body simulations covering a large cosmological volume at high resolution. We examine the HI mass function and the…

Cosmology and Nongalactic Astrophysics · Physics 2020-03-11 Marta Spinelli , Anna Zoldan , Gabriella De Lucia , Lizhi Xie , Matteo Viel

Predicting the statistical properties of the neutral hydrogen (HI) density field during reionization is an important step in using upcoming 21 cm observations to constrain models of reionization. Semi-numerical models of reionization are…

Cosmology and Nongalactic Astrophysics · Physics 2026-04-22 Gaurav Pundir , Tirthankar Roy Choudhury , Aseem Paranjape

We present a new method for modeling inhomogeneous cosmic reionization on large scales. Utilizing high-resolution radiation-hydrodynamic simulations with 2048^3 dark matter particles, 2048^3 gas cells, and 17 billion adaptive rays in a L =…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 Nick Battaglia , Hy Trac , Renyue Cen , Abraham Loeb
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