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reionization

M. Mapelli, A. Ferrara, E. Pierpaoli · 2007

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reionization

Karolina Zawada, Benoît Semelin, Patrick Vonlanthen et al. · 2016

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CEMPlifying reionization

Mahavir Sharma, Tom Theuns, Carlos S. Frenk · Monthly Notices of the Royal Astronomical Society · 2018

The massive stars that ionized the Universe have short lifetimes and can only be studied near the time of formation, but any low-mass stars that formed contemporaneously might be observable in the local Universe today. We study the abundance pattern and spatial distribution of these ‘siblings of reionizers’ (SoRs) in the eagle cosmological hydrodynamical simulation. SoRs tend to be enriched to supersolar levels in α-elements compared to iron, and we investigate the resemblance between SoRs and the observed stars that are enhanced in carbon. In eagle galaxies resembling the Milky Way, ∼40 per cent of carbon-enhanced metal poor (CEMP) stars are SoRs. Conversely, ∼10 per cent of all SoRs are CEMP stars. This fraction increases to ≳ 50 per cent for SoRs of metallicity [Fe/H] < −4, and at such low metallicities, most of the CEMP stars are of CEMP-no subtype that are lacking neutron capture elements. Although these numbers may well depend on the details of the physical models implemented in eagle, the trends we describe are robust as they result from the strong feedback from star formation in early galaxies, itself a key ingredient of most current models of galaxy formation. We further find that most SoRs today reside in haloes with mass Mh |$\gtrapprox$| 1012 M⊙, and 50 per cent of them are in the halo of their central galaxy (distance >10 kpc), mainly because they were accreted onto their current host rather than formed in situ. To a good approximation, the SoRs are CEMP-no stars that reside in the stellar haloes of massive galaxies, with nearly half of them contributing to the intracluster light in groups and clusters.

Cited by 5Open access

reionization, n.

Oxford University Press eBooks · 2023

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Cosmological reionization

Piero Madau · Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering Sciences · 2000

In popular cosmological scenarios, some time beyond a redshift of 10, stars within protogalaxies created the first heavy elements; these systems, together perhaps with an early population of quasars, generated the UV radiation and mechanical energy that reheated and reionized the cosmos. The history of the Universe during and soon after these crucial formative stages is recorded in the all–pervading intergalactic medium (IGM), which contains most of the ordinary baryonic material left over from the big bang. Throughout the epoch of structure formation, the IGM becomes clumpy and acquires peculiar motions under the influence of gravity, and acts as a source for the gas that gets accreted, cools and forms stars within galaxies, and as a sink for the metal–enriched material, energy and radiation that they eject.

Cited by 14Open access

Cosmological Reionization

Madau, Piero · arXiv (Cornell University) · 2000

In popular cosmological scenarios, some time beyond a redshift of 10, stars within protogalaxies created the first heavy elements; these systems, together perhaps with an early population of quasars, generated the ultraviolet radiation and mechanical energy that reheated and reionized the cosmos. The history of the Universe during and soon after these crucial formative stages is recorded in the all-pervading intergalactic medium (IGM), which contains most of the ordinary baryonic material left over from the big bang. Throughout the epoch of structure formation, the IGM becomes clumpy and acquires peculiar motions under the influence of gravity, and acts as a source for the gas that gets accreted, cools, and forms stars within galaxies, and as a sink for the metal enriched material, energy, and radiation which they eject.

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Cosmic Reionization

Massimo Stiavelli · 2009

This chapter contains sections titled: Overview The Properties of the Sources of Reionization Adding Realism to the Calculations Luminosity Function of Ionizing Sources Reionization by Population III Stars How Is the Intergalactic Medium Enriched? Reheating of the Intergalactic Medium Keeping the Intergalactic Medium Ionized Hints for Further Study

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Dust from reionization

E. Elfgren, F.–X. Désert · Astronomy and Astrophysics · 2004

The possibility that population III stars have reionized the Universe at redshifts greater than 6 has recently gained momentum with WMAP polarization results. Here we analyse the role of early dust produced by these stars and ejected into the intergalactic medium. We show that this dust, heated by the radiation from the same population III stars, produces a submillimetre excess. The electromagnetic spectrum of this excess could account for a significant fraction of the FIRAS (Far Infrared Absolute Spectrophotometer) cosmic far infrared background above 700 micron. This spectrum, a primary anisotropy () spectrum times the dust emissivity law, peaking in the submillimetre domain around 750 micron, is generic and does not depend on other detailed dust properties. Arcminute–scale anisotropies, coming from inhomogeneities in this early dust, could be detected by future submillimetre experiments such as Planck HFI.

Cited by 7Open access

Simulating IGM Reionization

Ciardi, B., Stoehr, F., White, S. D. M. · arXiv (Cornell University) · 2003

We have studied the IGM reionization process in its full cosmological context including structure evolution and a realistic galaxy population. We have used a combination of high-resolution N-body simulations (to describe the dark matter and diffuse gas component), a semi-analytic model of galaxy formation (to track the evolution of the sources of ionizing radiation) and the Monte Carlo radiative transfer code CRASH (to follow the propagation of ionizing photons into the IGM). The process has been followed in the largest volume ever used for this kind of study, a field region of the universe with a comoving length of L~20/h Mpc, embedded in a much larger cosmological simulation. To assess the effect of environment on the reionization process, the same radiative transfer simulations have been performed on a 10/h Mpc comoving box, centered on a clustered region. We find that, to account for the all ionizing radiation, objects with total masses of M~10^9 Msun must be resolved. In this case, the simulated stellar population produces a volume averaged ionization fraction x_v=0.999 by z~8, consistent with observations without requiring any additional sources of ionization. We also find that environment substantially affects the reionization process. In fact, although the simulated proto-cluster occupies a smaller volume and produces a higher number of ionizing photons, it gets totally ionized later. This is because high density regions, which are more common in the proto-cluster, are difficult to ionize because of their high recombination rates.

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signal of reionization

Bin Yue, Benedetta Ciardi, Evan Scannapieco et al. · 2009

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Dust from reionization

E. Elfgren, F.-X. Désert · Springer Link (Chiba Institute of Technology) · 2004

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Modeling cosmic reionization

Nickolay Y. Gnedin, Piero Madau · Living Reviews in Computational Astrophysics · 2022

Abstract The transformation of cold neutral intergalactic hydrogen into a highly ionized warm plasma marks the end of the cosmic dark ages and the beginning of the age of galaxies. The details of this process reflect the nature of the early sources of radiation and heat, the statistical characteristics of the large-scale structure of the Universe, the thermodynamics and chemistry of cosmic baryons, and the histories of star formation and black hole accretion. A number of massive data sets from new ground- and space-based instruments and facilities over the next decade are poised to revolutionize our understanding of primeval galaxies, the reionization photon budget, the physics of the intergalactic medium (IGM), and the fine-grained properties of hydrogen gas in the “cosmic web”. In this review, we survey the physics and key aspects of reionization-era modeling and describe the diverse range of computational techniques and tools currently available in this field.

Cited by 60Open access

Cosmic Reionization Redux

Gnedin, Nickolay Y., Fan, Xiaohui · arXiv (Cornell University) · 2006

We show that numerical simulations of reionization that resolve the Lyman Limit systems (and, thus, correctly count absorptions of ionizing photons) have converged to about 10% level for 5

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The Reionization Epoch

COJAZZI P., LUCCHIN F., BRESSAN A. et al. · Research Padua Archive (University of Padua) · 1999

We reconsider the problem of the reionization of the universe by means of stellar sources. Using the model developed by Haiman &amp; Loeb (1997), we focus on the effect of changing basic parameters, such as stellar models and spectra, adopted for finding the ionizing photons production rate. We find that the adoption of suitable zero metallicity models instead of even the most metal poor ones, usually adopted by other authors, significantly modifies the epoch at wich the Universe is reionized by the first stellar generations.

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Cosmic Reionization On Computers: Reionization Histories of Present-day Galaxies

Hanjue 珏 Zhu 朱涵, Camille Avestruz, Nickolay Y. Gnedin · The Astrophysical Journal · 2019

Abstract We examine the reionization history of present-day galaxies by explicitly tracing the building blocks of halos from the Cosmic Reionization On Computers project. We track dark matter particles that belong to z = 0 halos and extract the neutral fractions at corresponding positions during rapid global reionization. The resulting particle reionization histories allow us to explore different definitions of a halo’s reionization redshift and to account for the neutral content of the interstellar medium. Consistent with previous work, we find a systematic trend of reionization redshift with mass—present day halos with higher masses have earlier reionization times. Finally, we quantify the spread of reionization times within each halo, which also has a mass dependence.

Cited by 8Open access

Cosmic microwave background polarization and reionization: Constrainingmodels with a double reionization

L. P. L. Colombo, G. Bernardi, Luciano Casarini et al. · Astronomy and Astrophysics · 2005

Neutral hydrogen around high–z QSO and an optical depth can be reconciled if reionization is more complex than a single transition at . Tracing its details could shed a new light on the first sources of radiation. Here we discuss how far such details can be inspected through planned experiments on CMB large-scale anisotropy and polarization, by simulating an actual data analysis. By considering a set of double reionization histories of Cen (2003) type, a relevant class of models not yet considered by previous works, we confirm that large angle experiments rival high resolution ones in reconstructing the reionization history. We also confirm that reionization histories, studied with the prior of a single and sharp reionization, yield a biased , showing that this bias is generic. We further find a monotonic trend in the bias for the models that we consider, and propose an explanation of the trend, as well as the overall bias. We also show that in long-lived experiments such a trend can be used to discriminate between single and double reionization patterns.

Cited by 7Open access

Simulating Cosmic Reionization at Large Scales I: the Geometry of Reionization

Iliev, Ilian T., Mellema, Garrelt, Pen, Ue-Li et al. · arXiv (Cornell University) · 2005

We present the first large-scale radiative transfer simulations of cosmic reionization, in a simulation volume of (100/h Mpc)^3, while at the same time capturing the dwarf galaxies which are primarily responsible for reionization. We achieve this by combining the results from extremely large, cosmological, N-body simulations with a new, fast and efficient code for 3D radiative transfer, C^2-Ray. The resulting electron-scattering optical depth is in good agreement with the first-year WMAP polarization data. We show that reionization clearly proceeded in an inside-out fashion, with the high-density regions being ionized earlier, on average, than the voids. Ionization histories of smaller-size (5 to 10 comoving Mpc) subregions exibit a large scatter about the mean and do not describe the global reionization history well. The minimum reliable volume size for such predictions is ~30 Mpc. We derive the power-spectra of the neutral, ionized and total gas density fields and show that there is a significant boost of the density fluctuations in both the neutral and the ionized components relative to the total at arcminute and larger scales. We find two populations of HII regions according to their size, numerous, mid-sized (~10 Mpc) regions and a few, rare, very large regions tens of Mpc in size. We derive the statistical distributions of the ionized fraction and ionized gas density at various scales and for the first time show that both distributions are clearly non-Gaussian. (abridged)

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Little Red reionization factories

Fan Zhang · ArXiv.org · 2025

In this note, we suggest the possibility that an elucidation of the nature of the numerous Little Red Dots (LRDs) at high redshifts, may facilitate the resolution of another concurrent cosmic puzzle, namely reionization. Specifically, it is hypothesized that intergalactic HI gas is compelled by the tidal field associated with a growing gravitational entropy, in the form of gas streams, into colliding at the LRD sites. The resulting shock heating and compression encourage starburst activities, which subsequently photo-ionize the gas into HII, that in turn shines into the rest-optical via bremsstrahlung radiation within the minimal-timescale-cutoff (i.e., red) regime, before escaping back into the intergalactic space, propelled by the newly fusion-injected energy.

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The Epoch of Reionization

Marius B Eide · Electronic Theses of LMU Munich (Ludwig-Maximilians-Universität München) · 2020

The Epochs of Cosmic Heating and Reionization are the early times in which the Dark Ages of the Universe concluded with a Cosmic Dawn. Sometime during the first billion years, the first galaxies formed, and with them came the first sources of light. Their radiation heated and ionized the gas that spanned the space between galaxies. The details surrounding this phase transition is the topic of this thesis. Awaiting decisive radio telescope observations of the early Universe, we have undertaken the task of modelling and simulating Cosmic Dawn in an unprecedented manner. We assembled a framework in which we combined theoretical models of sources of heat, ionization and light with a simulation of cosmic structure (and hence galaxy) formation and used these in a high-precision radiative transfer simulation. This allowed us to predict the heating and reionization process. We assumed that stars, X-ray binary systems and the interstellar medium emit ionizing radiation that escape from all galaxies, and that the most massive galaxies also host massive black holes, whose accretion disks are sources of warming light. To predict the location and radiative properties of the sources, we used the (100 cMpc $h^{-1}$)$^3$ hydrodynamic simulation MassiveBlack-II as our cosmic environment. We traced the radiation with the multifrequency ionizing three-dimensional `Cosmic RAdiative transfer Scheme for Hydrodynamics', CRASH. Our main finding is that stars are likely to be the main driver of reionization of hydrogen gas. Black holes are the only sources that may fully ionize helium, thus we expect them to dominate helium reionization at later times. The gas temperature is determined by their main ionizer, the stars, but may be raised tens of thousands of degrees further if a black hole is in the vicinity. The interstellar medium and the X-ray binaries do not drive reionization, but nevertheless heat and ionize neutral intergalactic gas ever so slightly---sufficiently to leave distinct signatures to be observed with present and future radio telescopes. We also investigate the long-standing question of the role of black holes. Not all galaxies in the hydrodynamic simulation host one. Training a neural network on those that did, we mock black holes and place them into all galaxies. We predict a population of faint BHs that may provide a significant, but not dominant contribution to hydrogen reionization. Future ray tracing simulations are needed to predict their thermal signatures. We conclude this thesis with a call for future radio observations to be done from the Moon. Our branch of astronomy has the potential to usher humanity into a new era of collaboration and peaceful space exploration.

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Dust distribution during reionization

E. Elfgren, F.–X. Désert, B. Guiderdoni · Astronomy and Astrophysics · 2007

Context. The dust produced by the first generation of stars will be a foreground to cosmic microwave background.

Cited by 5Open access