Detecting the Rise and Fall of the First Stars by Their Impact on Cosmic Reionization

Ahn, Kyungjin; Iliev, Ilian T.; Shapiro, Paul R.; Mellema, Garrelt; Koda, Jun; Mao, Yi

doi:10.1088/2041-8205/756/1/l16

Cited by 125 publications

(197 citation statements)

References 46 publications

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“…Our simulations lack the resolution and the physics to follow the formation of stars in minihaloes, i.e., haloes with virial temperatures below 10 4 K. Ionization by these stars is expected to increase the optical depth by 0.03 (e.g., Shull & Venkatesan 2008;Ahn et al 2012;Wise et al 2014). If these stars evolve into accreting black holes, the optical depth may be further increased due to the pre-ionization of the IGM by X-rays (e.g., Ricotti & Ostriker 2004).…”

Section: Overview Of Simulationsmentioning

confidence: 99%

“…The optical depth towards reionization, τreion = zstart z=0 necdt, where ne is the number density of free electrons and zstart 30 is the redshift at which reionization begins, is an important integral constraint on the reionization history (e.g., Alvarez et al 2006;Shull & Venkatesan 2008;Ahn et al 2012). For the computation of the optical depth, we assume a hydrogen mass fraction X = 0.75, and that the fraction of ionized hydrogen is equal to that in our simulations, which assume X = 1.…”

Section: Overview Of Simulationsmentioning

confidence: 99%

“…This early population of stars may preionize the IGM and provide a significant feedback on subsequent star formation and reionization (e.g., Ricotti & Ostriker 2004b;Ahn et al 2012). Our simulations have also ignored the enrichment with metals that accompanies the explosion of stars as SNe.…”

Section: Limitationsmentioning

confidence: 99%

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Spatially adaptive radiation-hydrodynamical simulations of galaxy formation during cosmological reionization

Pawlik

Schaye

Vecchia

2015

Monthly Notices of the Royal Astronomical Society

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We present a suite of cosmological radiation-hydrodynamical simulations of the assembly of galaxies driving the reionization of the intergalactic medium (IGM) at z 6. The simulations account for the hydrodynamical feedback from photoionization heating and the explosion of massive stars as supernovae (SNe). Our reference simulation, which was carried out in a box of size 25 h −1 comoving Mpc using 2 × 512 3 particles, produces a reasonable reionization history and matches the observed UV luminosity function of galaxies. Simulations with different box sizes and resolutions are used to investigate numerical convergence, and simulations in which either SNe or photoionization heating or both are turned off, are used to investigate the role of feedback from star formation. Ionizing radiation is treated using accurate radiative transfer at the high spatially adaptive resolution at which the hydrodynamics is carried out. SN feedback strongly reduces the star formation rates (SFRs) over nearly the full mass range of simulated galaxies and is required to yield SFRs in agreement with observations. Photoheating helps to suppress star formation in low-mass galaxies, but its impact on the cosmic SFR is small. Because the effect of photoheating is masked by the strong SN feedback, it does not imprint a signature on the UV galaxy luminosity function, although we note that our resolution is insufficient to model star-forming minihaloes cooling through molecular hydrogen transitions. Photoheating does provide a strong positive feedback on reionization because it smooths density fluctuations in the IGM, which lowers the IGM recombination rate substantially. Our simulations demonstrate a tight non-linear coupling of galaxy formation and reionization, motivating the need for the accurate and simultaneous inclusion of photoheating and SN feedback in models of the early Universe.

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Section: Overview Of Simulationsmentioning

confidence: 99%

Section: Overview Of Simulationsmentioning

confidence: 99%

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Spatially adaptive radiation-hydrodynamical simulations of galaxy formation during cosmological reionization

Pawlik

Schaye

Vecchia

2015

Monthly Notices of the Royal Astronomical Society

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“…Indeed most reionization simulations in large boxes used to implement atomic-cooling halos only, while this may underestimate the photon budget in the early stage of reionization. In a large-scale (box size of 114/h Mpc comoving) simulation of cosmic reionization (with ray-tracing method), Ahn et al (2012) used the conditional halo bias found in Section 4.2.1 of this paper to include minihaloes, which could not otherwise have been realized due to numerical resolution. This way, they could span the full dynamic range of haloes -both minihaloes and atomic-cooling haloes -responsible for emitting hydrogen-ionizing and H2-dissociation radiation, and observed that the reionization process is extended further in time to comply better with several observational constraints.…”

Section: Introductionmentioning

confidence: 99%

Non-linear bias of cosmological halo formation in the early universe

Ahn

Iliev

Shapiro

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We present estimates of the nonlinear bias of cosmological halo formation, spanning a wide range in the halo mass from ∼ 10 5 M ⊙ to ∼ 10 12 M ⊙ , based upon both a suite of high-resolution cosmological N-body simulations and theoretical predictions. The halo bias is expressed in terms of the mean bias and stochasticity as a function of local overdensity (δ), under different filtering scales, which is realized as the density of individual cells in uniform grids. The sampled overdensities span a range wide enough to provide the fully nonlinear bias effect on the formation of haloes. A strong correlation between δ and halo population overdensity δ h is found, along with sizable stochasticity. We find that the empirical mean halo bias matches, with good accuracy, the prediction by the peak-background split method based on the excursion set formalism, as long as the empirical, globally-averaged halo mass function is used. Consequently, this bias formalism is insensitive to uncertainties caused by varying halo identification schemes, and can be applied generically. We also find that the probability distribution function of biased halo numbers has wider distribution than the pure Poisson shot noise, which is attributed to the sub-cell scale halo correlation. We explicitly calculate this correlation function and show that both overdense and underdense regions have positive correlation, leading to stochasticity larger than the Poisson shot noise in the range of haloes and halo-collapse epochs we study.

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“…Recently, an additional simulation was performed, including this new physics, in an even larger volume (∼ 600 Mpc; I. T. Iliev et al, in preparation). Ahn et al (2012) expanded the mass range even further by accounting for starlight emitted by minihalos (10 5 -10 8 M ) as well. In addition to their Jeans-mass filtering in ionized regions, they may also be suppressed if molecular hydrogen in minihalos is photodissociated by Lyman-Werner (LW) band photons in the UV background below 13.6 eV also emitted by the sources of reionization.…”

Section: Introductionmentioning

confidence: 99%

The Kinetic Sunyaev-Zel'dovich Effect as a Probe of the Physics of Cosmic Reionization: The Effect of Self-regulated Reionization

Park¹

2014

Proceedings of Frank N. Bash Symposium 2013: New Horizons in Astronomy — PoS(BASH 2013)

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We calculate the angular power spectrum of the cosmic microwave background temperature fluctuations induced by the kinetic Sunyaev-Zel'dovich (kSZ) effect from the epoch of reionization (EOR). We use detailed N-body+radiative-transfer simulations to follow inhomogeneous reionization of the intergalactic medium. For the first time, we take into account the "self-regulation" of reionization: star formation in low-mass dwarf galaxies (10 8 M M 10 9 M ) or minihalos (10 5 M M 10 8 M ) is suppressed if these halos form in the regions that were already ionized or Lyman-Werner dissociated. Some previous work suggested that the amplitude of the kSZ power spectrum from the EOR can be described by a two-parameter family: the epoch of half-ionization and the duration of reionization. However, we argue that this picture applies only to simple forms of the reionization history which are roughly symmetric about the half-ionization epoch. In self-regulated reionization, the universe begins to be ionized early, maintains a low level of ionization for an extended period, and then finishes reionization as soon as high-mass atomically cooling halos dominate. While inclusion of self-regulation affects the amplitude of the kSZ power spectrum only modestly (∼10%), it can change the duration of reionization by a factor of more than two. We conclude that the simple two-parameter family does not capture the effect of a physical, yet complex, reionization history caused by self-regulation. When added to the post-reionization kSZ contribution, our prediction for the total kSZ power spectrum is below the current upper bound from the South Pole Telescope. Therefore, the current upper bound on the kSZ effect from the EOR is consistent with our understanding of the physics of reionization.

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Detecting the Rise and Fall of the First Stars by Their Impact on Cosmic Reionization

Cited by 125 publications

References 46 publications

Spatially adaptive radiation-hydrodynamical simulations of galaxy formation during cosmological reionization

Spatially adaptive radiation-hydrodynamical simulations of galaxy formation during cosmological reionization

Non-linear bias of cosmological halo formation in the early universe

The Kinetic Sunyaev-Zel'dovich Effect as a Probe of the Physics of Cosmic Reionization: The Effect of Self-regulated Reionization

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