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Astronomers reveal remarkable simulations of the early universe epoch of reionization


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Astronomers reveal remarkable simulations of the early universe

It looks like fireflies flickering in the darkness. Slowly, more and more amass, lighting up the screen in large chunks and clusters.


But this is not a video about insects. It's a simulation of the early universe, a time after the Big Bang when the cosmos transformed from a place of utter darkness to a radiant, light-filled environment.

The stunning video is part of a large suite of simulations described in a series of three papers accepted to the Monthly Notices of the Royal Astronomical Society. Created by researchers at the Center for Astrophysics | Harvard & Smithsonian, the Massachusetts Institute of Technology and the Max Planck Institute for Astrophysics, the simulations represent a monumental advancement in simulating the formation of the first galaxies and reionization—the process by which neutral hydrogen atoms in space were transformed into positively charged, or ionized, hydrogen, allowing light to spread throughout the universe.

The simulated period, known as the epoch of reionization, took place some 13 billion years ago and was challenging to reconstruct, as it involves immensely complicated, chaotic interactions, including those between gravity, gas and radiation, or light.

more at link......................

the paper:


The THESAN project: Lyman-α emission and transmission during the Epoch of Reionization



The visibility of high-redshift Lyman-alpha emitting galaxies (LAEs) provides important constraints on galaxy formation processes and the Epoch of Reionization (EoR). However, predicting realistic and representative statistics for comparison with observations represents a significant challenge in the context of large-volume cosmological simulations. The THESAN project offers a unique framework for addressing such limitations by combining state-of-the-art galaxy formation (IllustrisTNG) and dust models with the AREPO-RT radiation-magneto-hydrodynamics solver. In this initial study we present Lyman-alpha centric analysis for the flagship simulation that resolves atomic cooling haloes throughout a (95.5 cMpc)3 region of the Universe. To avoid numerical artifacts we devise a novel method for accurate frequency-dependent line radiative transfer in the presence of continuous Hubble flow, transferable to broader astrophysical applications as well. Our scalable approach highlights the utility of LAEs and red damping-wing transmission as probes of reionization, which reveal nontrivial trends across different galaxies, sightlines, and frequency bands that can be modelled in the framework of covering fractions. In fact, after accounting for environmental factors influencing large-scale ionized bubble formation such as redshift and UV magnitude, the variation across galaxies and sightlines mainly depends on random processes including peculiar velocities and self-shielded systems that strongly impact unfortunate rays more than others. Throughout the EoR local and cosmological optical depths are often greater than or less than unity such that the exp ( − τ) behaviour leads to anisotropic and bimodal transmissivity. Future surveys will benefit by targeting both rare bright objects and Goldilocks zone LAEs to infer the presence of these (un)predictable (dis)advantages.

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