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Abraham Loeb - One of the best experts on this subject based on the ideXlab platform.
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precise measurement of the Reionization optical depth from the global 21 cm signal accounting for cosmic heating
The Astrophysical Journal, 2016Co-Authors: Anastasia Fialkov, Abraham LoebAbstract:As a result of our limited data on Reionization, the total optical depth for electron scattering, �, limits precision measurements of cosmological parameters from the Cosmic Microwave Background (CMB). It was recently shown that the predicted 21-cm signal of neutral hydrogen contains enough information to reconstructwith sub-percent accuracy, assuming that the neutral gas was much hotter than the CMB throughout the entire epoch of Reionization. Here we relax this assumption and use the global 21-cm signal alone to extractfor realistic X-ray heating scenarios. We test our model- independent approach using mock data for a wide range of ionization and heating histories and show that an accurate measurement of the Reionization optical depth at a sub-percent level is possible in most of the considered scenarios even when heating is not saturated during the epoch of Reionization, assuming that the foregrounds are mitigated. However, we find that in cases where heating sources had hard X-ray spectra and their luminosity was close to or lower than what is predicted based on low-redshift observations, the global 21-cm signal alone is not a good tracer of the Reionization history. Subject headings: cosmology: cosmological parameters, dark ages, Reionization, first stars; X-rays: binaries, galaxies, general
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gauging the contribution of x ray sources to Reionization through the kinetic sunyaev zel dovich effect
Journal of Cosmology and Astroparticle Physics, 2012Co-Authors: Eli Visbal, Abraham LoebAbstract:Measurements of the kinetic Sunyaev-Zel'dovich (kSZ) effect from instruments such as the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT) will soon put improved constraints on Reionization. Popular models assume that UV photons alone are responsible for Reionization of the intergalactic medium. We explore the effects of a significant contribution of X-rays to Reionization on the kSZ signal. Because X-rays have a large mean free path through the neutral intergalactic medium, they introduce partial ionization in between the sharp-edged bubbles created by UV photons. This smooth ionization component changes the power spectrum of the cosmic microwave background (CMB) temperature anisotropies. We quantify this effect by running semi-numerical simulations of Reionization. We test a number of different models of Reionization without X-rays that have varying physical parameters, but which are constrained to have similar total optical depths to electron scattering. These are then compared to models with varying levels of contribution to Reionization from X-rays. We find that models with more than a 10% contribution from X-rays produce a significantly lower power spectrum of temperature anisotropies than all the UV-only models tested. The expected sensitivity of SPT and ACT may be insufficient to distinguish between our models, however, a non-detection of the kSZ signal from the epoch of Reionization could result from the contribution of X-rays. It will be important for future missions with improved sensitivity to consider the impact of X-ray sources on Reionization.
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imprint of inhomogeneous hydrogen Reionization on the temperature distribution of the intergalactic medium
The Astrophysical Journal, 2008Co-Authors: Hy Trac, Renyue Cen, Abraham LoebAbstract:We study the impact of inhomogeneous hydrogen Reionization on the thermal evolution of the intergalactic medium (IGM) using hydrodynamic + radiative transfer simulations where Reionization is completed either early ( -->z ~ 9) or late ( -->z ~ 6). In general, we find that low-density gas near large-scale overdensities is ionized and heated earlier than gas in the large-scale, underdense voids. Furthermore, at a later time the IGM temperature is inversely related to the Reionization redshift because gas that is heated earlier has more time to cool through adiabatic expansion and Compton scattering. Thus, at the end of Reionization the median temperature-density relation is an inverted power law with slope -->γ − 1 ~ − 0.2, in both models. However, at fixed density there is up to order unity scatter in the temperature due to the distribution of Reionization redshifts. Because of the complex equation of state, the evolved IGM temperature-density relations for the redshift range -->4 z 6 can still have significant curvature and scatter. These features must be taken into account when interpreting the Lyα absorption in high-redshift quasar spectra.
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The imprint of cosmic Reionization on galaxy clustering
Monthly Notices of the Royal Astronomical Society, 2007Co-Authors: J. Stuart B. Wyithe, Abraham LoebAbstract:We consider the effect of Reionization on the clustering properties of galaxy samples at intermediate redshifts (z ∼ 0.3-5.5). Current models for the Reionization of intergalactic hydrogen predict that overdense regions will be reionized early, thus delaying the build-up of stellar mass in the progenitors of massive lower redshift galaxies. As a result, the stellar populations observed in intermediate-redshift galaxies are somewhat younger and hence brighter in overdense regions of the Universe. Galaxy surveys would therefore be sensitive to galaxies with a somewhat lower dark matter mass in overdense regions. The corresponding increase in the observed number density of galaxies can be parametrized as a galaxy bias due to Reionization. We model this process using merger trees combined with a stellar synthesis code. Our model demonstrates that Reionization has a significant effect on the clustering properties of galaxy samples that are selected based on their star formation properties. The bias correction in Lyman-break galaxies (including those in proposed baryonic oscillation surveys at z < 1) is at the level of 10-20 per cent for a halo mass of 10 12 M ⊙ , leading to corrections factors of 1.5-2 in the halo mass inferred from measurements of clustering length. The Reionization of helium could also lead to a sharp increase in the amplitude of the galaxy correlation function at z ∼ 3. We find that the Reionization bias is approximately independent of scale and halo mass. However, since the traditional galaxy bias is mass dependent, the Reionization bias becomes relatively more important for lower mass systems. The correction to the bias due to Reionization is very small in surveys of luminous red galaxies at z < 1.
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Is Double Reionization Physically Plausible
The Astrophysical Journal, 2005Co-Authors: Steven R Furlanetto, Abraham LoebAbstract:Recent observations of z ~ 6 quasars and the cosmic microwave background imply a complex history of cosmic Reionization. Such a history requires some form of feedback to extend Reionization over a long time interval, but the nature of the feedback and how rapidly it operates remain highly uncertain. Here we focus on one aspect of this complexity: which physical processes can cause the global ionized fraction to evolve nonmonotonically with cosmic time? We consider a range of mechanisms and conclude that double Reionization is much less likely than a long, but still monotonic, ionization history. We first examine how galactic winds affect the transition from metal-free to normal star formation. Because the transition is actually spatially inhomogeneous and temporally extended, this mechanism cannot be responsible for double Reionization, given plausible parameters for the winds. We next consider photoheating, which causes the cosmological Jeans mass to increase in ionized regions and hence suppresses galaxy formation there. In this case, double Reionization requires that small halos form stars efficiently, that the suppression from photoheating is strong relative to current expectations, and that ionizing photons are preferentially produced outside previously ionized regions. Finally, we consider H2 photodissociation, in which the buildup of a soft ultraviolet background suppresses star formation in small halos. This can in principle cause the ionized fraction to temporarily decrease, but only during the earliest stages of Reionization. Finally, we briefly consider the effects of some of these feedback mechanisms on the topology of Reionization.
Matthew Mcquinn - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic Response of the Intergalactic Medium to Reionization
The Astrophysical Journal, 2020Co-Authors: Anson D'aloisio, Matthew Mcquinn, Hy Trac, Christopher Cain, Andrei MesingerAbstract:The intergalactic medium is expected to clump on scales down to $10^4-10^8$ M$_{\odot}$ before the onset of Reionization. The impact of these small-scale structures on Reionization is poorly understood despite the modern understanding that gas clumpiness limits the growth of H II regions. We use a suite of radiation-hydrodynamics simulations that capture the $\sim 10^4$ M$_{\odot}$ Jeans mass of unheated gas to study density fluctuations during Reionization. Our simulations track the complex ionization and hydrodynamical response of gas in the wake of ionization fronts. The clumping factor of ionized gas (proportional to the recombination rate) rises to a peak value of $5-20$ approximately $\Delta t = 10$ Myr after ionization front passage, depending on the incident intensity, redshift, and degree to which the gas had been pre-heated by the first X-ray sources. The clumping factor reaches its relaxed value of $\approx 3$ by $\Delta t = 300$ Myr. The mean free path of Lyman-limit photons evolves in unison, being up to several times shorter in un-relaxed, recently reionized regions compared to those that were reionized much earlier. Assessing the impact of this response on the global reionizaton process, we find that un-relaxed gaseous structures boost the total number of recombinations by $\approx 50$ % and lead to spatial fluctuations in the mean free path that persist appreciably for several hundred million years after the completion of Reionization.
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Heating of the Intergalactic Medium by Hydrogen Reionization
The Astrophysical Journal, 2019Co-Authors: Anson D'aloisio, Matthew Mcquinn, Hy Trac, Frederick B. Davies, Oliver Maupin, Spencer Fuller, Phoebe R. Upton SanderbeckAbstract:During Reionization, the intergalactic medium is heated impulsively by supersonic ionization fronts (I-fronts). The peak gas temperatures behind the I-fronts, $T_\mathrm{reion}$, are a key uncertainty in models of the thermal history after Reionization. Here we use high-resolution radiative transfer simulations to study the parameter space of $T_\mathrm{reion}$. We show that $T_\mathrm{reion}$ is only mildly sensitive to the spectrum of incident radiation over most of the parameter space, with temperatures set primarily by I-front speeds. We also explore what current models of Reionization predict for $T_\mathrm{reion}$ by measuring I-front speeds in cosmological radiative transfer simulations. We find that the post-I-front temperatures evolve toward hotter values as Reionization progresses. Temperatures of $T_\mathrm{reion} = 17,000-22,000$ K are typical during the first half of Reionization, but $T_\mathrm{reion} = 25,000 - 30,000$ K may be achieved near the end of this process if I-front speeds reach $\sim10^4$ km/s as found in our simulations. Shorter Reionization epochs lead to hotter $T_\mathrm{reion}$. We discuss implications for $z>5$ Ly$\alpha$ forest observations, which potentially include sight lines through hot, recently reionized patches of the Universe. Interpolation tables from our parameter space study are made publicly available, along with a simple fit for the dependence of $T_\mathrm{reion}$ on the I-front speed.
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the kinetic sunyaev zel dovich signal from inhomogeneous Reionization a parameter space study
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: Andrei Mesinger, Matthew Mcquinn, David N SpergelAbstract:Inhomogeneous Reionization acts as a source of arcminute-scale anisotropies in the cosmic microwave background (CMB), the most important of which is the kinetic Sunyaev–Zel’dovich (kSZ) effect. Observational efforts with the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT) are poised to detect this signal for the first time, with projected 1 μ K2-level sensitivity to the dimensionless kSZ power spectrum around a multipole of l= 3000, [Δl3000]2. Indeed, recent SPT measurements place a bound of [Δl3000 ]2 < 2.8 μ K2 at 95 per cent confidence level, which degrades to [Δl3000 ]2 < 6 μ K2 if a significant correlation between the thermal Sunyaev–Zel’dovich (tSZ) effect and the cosmic infrared background (CIB) is allowed. To interpret these and upcoming observations, we compute the kSZ signal from a suite of ≈100 Reionization models using the publicly available code 21cmfast. Our physically motivated Reionization models are parametrized by the ionizing efficiency of high-redshift galaxies, the minimum virial temperature of haloes capable of hosting stars, and the ionizing photon mean free path – a parametrization motivated by previous theoretical studies of Reionization. We predict the contribution of patchy Reionization to the l= 3000 kSZ power to be 1.5–3.5 μ K2. Therefore, even when adopting the lowest estimate in the literature for the post-Reionization signal of , none of our models are consistent with the aggressive 2σ SPT bound that does not include correlations. This implies the following: (i) the early stages of Reionization occurred in a much more homogeneous manner than suggested by the stellar-driven scenarios we explore, such as would be the case if, e.g. very high energy X-rays or exotic particles contributed significantly and/or (ii) that there is a significant correlation between the CIB and the tSZ. The later is perhaps not surprising, as massive haloes should host both hot gas and star-forming galaxies. On the other hand, the conservative SPT bound of [Δl3000 ]2≲ 6 μ K2 is compatible with all of our models and is on the threshold of constraining physically motivated Reionization models. The largest patchy kSZ signals correspond to an extended Reionization process, in which the sources of ionizing photons are abundant and there are many recombinations (absorptions in sinks). We point out that insights into the astrophysics of the early Universe are encoded in both the amplitude and shape of the kSZ power spectrum.
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Studying Reionization with Ly-alpha Emitters
Monthly Notices of the Royal Astronomical Society, 2007Co-Authors: Matthew Mcquinn, Lars Hernquist, Matias Zaldarriaga, Suvendra DuttaAbstract:We show that observations of high-redshift Ly-alpha emitters (LAEs) have the potential to provide definitive evidence for Reionization in the near future. Using 200 Mpc radiative transfer simulations, we calculate the effect that patchy Reionization has on the line profile, on the luminosity function, and, most interestingly, on the clustering of emitters for several realistic models of Reionization. Reionization increases the measured clustering of emitters, and we show that this enhancement would be essentially impossible to attribute to anything other than Reionization. Our results motivate looking for the signature of Reionization in existing LAE data. We find that for stellar Reionization scenarios the angular correlation function of the 58 LAEs in the Subaru Deep Field z = 6.6 photometric sample is more consistent with a fully ionized universe (mean volume ionized fraction x_i = 1) than a universe with x_i 2-sigma confidence level. Measurements in the next year on Subaru will increase their z = 6.6 LAE sample by a factor of five and tighten these limits. If the clustering signature of Reionization is detected in a LAE survey, a comparison with a Lyman-break or a H-alpha survey in the same field would confirm the Reionization hypothesis. We discuss the optimal LAE survey specifications for detecting Reionization, with reference to upcoming programs.
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The kinetic Sunyaev Zel’dovich effect from Reionization
New Astronomy Reviews, 2006Co-Authors: Matthew Mcquinn, Steven R Furlanetto, Lars Hernquist, Oliver Zahn, Matias ZaldarriagaAbstract:Abstract During the epoch of Reionization, local variations in the ionized fraction (patchiness) imprint arcminute-scale temperature anisotropies in the cosmic microwave background through the kinetic Sunyaev–Zel’dovich (kSZ) effect. We employ an analytic model of Reionization devised by Furlanetto and coworkers to calculate the kSZ anisotropies for patchy Reionization. We find that the angular power spectrum of the kSZ anisotropies depends strongly on the size distribution of the HII bubbles and on the duration of Reionization. In addition, we show that upcoming measurements of the kSZ effect should be able to distinguish between several popular Reionization scenarios. In particular, the amplitude of the patchy power spectrum for Reionization scenarios in which the IGM is significantly ionized by Population III stars (or by mini-quasars/decaying particles) can be larger (or smaller) by over a factor of 3 than the amplitude in more traditional Reionization histories (with temperature anisotropies that range between 0.5 and 3 μK at l = 5000).
Ilian T. Iliev - One of the best experts on this subject based on the ideXlab platform.
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The H i bias during the Epoch of Reionization
Monthly Notices of the Royal Astronomical Society, 2019Co-Authors: Bin Yue, Hy Trac, Ilian T. Iliev, Liang Gao, Xuelei ChenAbstract:The neutral hydrogen (HI) and its 21 cm line are promising probes to the Reionization process of the intergalactic medium (IGM). To use this probe effectively, it is imperative to have a good understanding on how the neutral hydrogen traces the underlying matter distribution. Here we study this problem using semi-numerical modeling by combining the HI in the IGM and the HI from halos during the epoch of Reionization (EoR), and investigate the evolution and the scale-dependence of the neutral fraction bias as well as the 21 cm line bias. We find that the neutral fraction bias on large scales is negative during Reionization, and its absolute value on large scales increases during the early stage of Reionization and then decreases during the late stage. During the late stage of Reionization, there is a transition scale at which the HI bias transits from negative on large scales to positive on small scales, and this scale increases as the Reionization proceeds to the end.
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The Inhomogeneous Reionization Times of Present-day Galaxies
The Astrophysical Journal, 2018Co-Authors: Dominique Aubert, Nicolas Deparis, Pierre Ocvirk, Gustavo Yepes, Yehuda Hoffman, Ilian T. Iliev, Paul R. Shapiro, Stefan Gottloeber, Romain TeyssierAbstract:Today's galaxies experienced cosmic Reionization at different times in different locations. For the first time, Reionization ($50\%$ ionized) redshifts, $z_R$, at the location of their progenitors are derived from new, fully-coupled radiation-hydrodynamics simulation of galaxy formation and Reionization at $z > 6$, matched to N-body simulation to z = 0. Constrained initial conditions were chosen to form the well-known structures of the local universe, including the Local Group and Virgo, in a (91 Mpc)$^3$ volume large enough to model both global and local Reionization. Reionization simulation CoDa I-AMR, by CPU-GPU code EMMA, used (2048)$^3$ particles and (2048)$^3$ initial cells, adaptively-refined, while N-body simulation CoDa I-DM2048, by Gadget2, used (2048)$^3$ particles, to find Reionization times for all galaxies at z = 0 with masses $M(z=0)\ge 10^8 M_\odot$. Galaxies with $M(z=0) \gtrsim 10^{11} M_\odot$ reionized earlier than the universe as a whole, by up to $\sim$ 500 Myrs, with significant scatter. For Milky-Way-like galaxies, $z_R$ ranged from 8 to 15. Galaxies with $M(z=0) \lesssim 10^{11} M_\odot$ typically reionized as late or later than globally-averaged $50\%$ Reionization at $\langle z_R\rangle =7.8$, in neighborhoods where Reionization was completed by external radiation. The spread of Reionization times within galaxies was sometimes as large as the galaxy-to-galaxy scatter. The Milky Way and M31 reionized earlier than global Reionization but later than typical for their mass, neither dominated by external radiation. Their most massive progenitors at $z>6$ had $z_R$ = 9.8 (MW) and 11 (M31), while their total masses had $z_R$ = 8.2 (both).
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Suppression of star formation in low-mass galaxies caused by the Reionization of their local neighbourhood
Mon.Not.Roy.Astron.Soc., 2018Co-Authors: Taha Dawoodbhoy, Dominique Aubert, Pierre Ocvirk, Nicolas Gillet, Gustavo Yepes, Ilian T. Iliev, Paul R. Shapiro, Jun-hwan Choi, Romain Teyssier, Stefan GottlöberAbstract:Photoheating associated with Reionization suppressed star formation in low-mass galaxies. Reionization was inhomogeneous, however, affecting different regions at different times. To establish the causal connection between Reionization and suppression, we must take this local variation into account. We analyze the results of CoDa (‘Cosmic Dawn’) I, the first fully coupled radiation-hydrodynamical simulation of Reionization and galaxy formation in the Local Universe, in a volume large enough to model Reionization globally but with enough resolving power to follow all atomic-cooling galactic halos in that volume. For every halo identified at a given time, we find the redshift at which the surrounding IGM reionized, along with its instantaneous star formation rate (‘SFR’) and baryonic gas-to-dark matter ratio (|$M_\rm{gas}/M_{\small DM}$|). The average SFR per halo with M < 10^9M_⊙ was steady in regions not yet reionized, but declined sharply following local Reionization. For M > 10^10M_⊙, this SFR continued through local Reionization, increasing with time, instead. For 10^9M_⊙ < M < 10^10M_⊙, the SFR generally increased modestly through Reionization, followed by a modest decline. In general, halo SFRs were higher for regions that reionized earlier. A similar pattern was found for |$M_\rm{gas}/M_{\small DM}$|, which declined sharply following local Reionization for M < 10^9M_⊙. Local Reionization time correlates with local matter overdensity, which determines the local rates of structure formation and ionizing photon consumption. The earliest patches to develop structure and reionize ultimately produced more stars than they needed to finish and maintain their own Reionization, exporting their ‘surplus’ starlight to help reionize regions that developed structure later.
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The Inhomogeneous Reionization Times of Present-day Galaxies
Astrophys.J.Lett., 2018Co-Authors: Dominique Aubert, Nicolas Deparis, Pierre Ocvirk, Stefan Gottlöber, Gustavo Yepes, Yehuda Hoffman, Ilian T. Iliev, Paul R. Shapiro, Romain TeyssierAbstract:Today’s galaxies experienced cosmic Reionization at different times in different locations. For the first time, Reionization (50% ionized) redshifts, z R , at the location of their progenitors are derived from new, fully coupled radiation-hydrodynamics simulation of galaxy formation and Reionization at z > 6, matched to N-body simulation to z = 0. Constrained initial conditions were chosen to form the well-known structures of the local universe, including the Local Group and Virgo, in a (91 Mpc)3 volume large enough to model both global and local Reionization. Reionization simulation CoDa I-AMR, by CPU-GPU code EMMA, used (2048)3 particles and (2048)3 initial cells, adaptively refined, while N-body simulation CoDa I-DM2048, by Gadget2, used (2048)3 particles, to find Reionization times for all galaxies at z = 0 with masses M(z = 0) ≥ 108 M ⊙. Galaxies with reionized earlier than the universe as a whole, by up to ∼500 Myr, with significant scatter. For Milky Way–like galaxies, z R ranged from 8 to 15. Galaxies with typically reionized as late or later than globally averaged 50% Reionization at , in neighborhoods where Reionization was completed by external radiation. The spread of Reionization times within galaxies was sometimes as large as the galaxy-to-galaxy scatter. The Milky Way and M31 reionized earlier than global Reionization but later than typical for their mass, neither dominated by external radiation. Their most-massive progenitors at z > 6 had z R =9.8 (MW) and 11 (M31), while their total masses had z R = 8.2 (both).
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THE KINETIC SUNYAEV-ZEL'DOVICH EFFECT AS A PROBE OF THE PHYSICS OF COSMIC Reionization : THE EFFECT OF SELF-REGULATED Reionization
The Astrophysical Journal, 2013Co-Authors: Hyunbae Park, Ilian T. Iliev, Paul R. Shapiro, Eiichiro Komatsu, Kyungjin Ahn, Garrelt MellemaAbstract:We calculate the angular power spectrum of the Cosmic Microwave Background (CMB) 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 (IGM). For the first time we take into account the "self-regulation" of Reionization: star formation in low-mass dwarf galaxies (10^8 M_\sun \lesssim M \lesssim 10^9 M_\sun) or minihalos (10^5 M_\sun \lesssim M \lesssim 10^8 M_\sun) 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 (\sim 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.
C L Chang - One of the best experts on this subject based on the ideXlab platform.
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cosmic microwave background constraints on the duration and timing of Reionization from the south pole telescope
The Astrophysical Journal, 2012Co-Authors: O Zahn, Adam Lidz, C L Reichardt, L Shaw, K A Aird, B A Benson, L E Bleem, J E Carlstrom, C L ChangAbstract:The epoch of Reionization is a milestone of cosmological structure formation, marking the birth of the first objects massive enough to yield large numbers of ionizing photons. However, the mechanism and timescale of Reionization remain largely unknown. Measurements of the cosmic microwave background (CMB) Doppler effect from ionizing bubbles embedded in large-scale velocity streams—known as the patchy kinetic Sunyaev-Zel'dovich (kSZ) effect—can be used to constrain the duration of Reionization. When combined with large-scale CMB polarization measurements, the evolution of the ionized fraction, x-bar_(e), can be inferred. Using new multi-frequency data from the South Pole Telescope (SPT), we show that the ionized fraction evolved relatively rapidly. For our basic foreground model, we find the kSZ power sourced by Reionization at l = 3000 to be D^(patchy)_3000 ≤ 2.1 μK^2 at 95% confidence. Using Reionization simulations, we translate this to a limit on the duration of Reionization of Δz≡z_(x-bar)_e=0.20 - z_(x-bar)_e=0.99≤4.4 (95% confidence). We find that this constraint depends on assumptions about the angular correlation between the thermal SZ power and the cosmic infrared background (CIB). Introducing the degree of correlation as a free parameter, we find that the limit on kSZ power weakens to D^(patchy)_3000 ≤ 4.9 μK^2, implying Δz ≤ 7.9 (95% confidence). We combine the SPT constraint on the duration of Reionization with the Wilkinson Microwave Anisotropy Probe measurement of the integrated optical depth to probe the cosmic ionization history. We find that Reionization ended with 95% confidence at z > 7.2 under the assumption of no tSZ-CIB correlation, and z > 5.8 when correlations are allowed. Improved constraints from the full SPT data set in conjunction with upcoming Herschel and Planck data should detect extended Reionization at >95% confidence provided Δz ≥ 2. These CMB observations complement other observational probes of the epoch of Reionization such as the redshifted 21 cm line and narrowband surveys for Lyα-emitting galaxies.
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cosmic microwave background constraints on the duration and timing of Reionization from the south pole telescope
arXiv: Cosmology and Nongalactic Astrophysics, 2011Co-Authors: O Zahn, Adam Lidz, C L Reichardt, L Shaw, K A Aird, B A Benson, L E Bleem, J E Carlstrom, C L ChangAbstract:The epoch of Reionization is a milestone of cosmological structure formation, marking the birth of the first objects massive enough to yield large numbers of ionizing photons. The mechanism and timescale of Reionization remain largely unknown. Measurements of the CMB Doppler effect from ionizing bubbles embedded in large-scale velocity streams (the patchy kinetic Sunyaev-Zel'dovich effect) can constrain the duration of Reionization. When combined with large-scale CMB polarization measurements, the evolution of the ionized fraction can be inferred. Using new multi-frequency data from the South Pole Telescope (SPT), we show that the ionized fraction evolved relatively rapidly. For our basic foreground model, we find the kinetic Sunyaev-Zel'dovich power sourced by Reionization at l=3000 to be 7.2 under the assumption of no tSZ-CIB correlation, and z>5.8 when correlations are allowed. Improved constraints from the full SPT data set in conjunction with upcoming Herschel and Planck data should detect extended Reionization at >95% CL provided Delta z >= 4. (abbreviated)
Garrelt Mellema - One of the best experts on this subject based on the ideXlab platform.
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THE KINETIC SUNYAEV-ZEL'DOVICH EFFECT AS A PROBE OF THE PHYSICS OF COSMIC Reionization : THE EFFECT OF SELF-REGULATED Reionization
The Astrophysical Journal, 2013Co-Authors: Hyunbae Park, Ilian T. Iliev, Paul R. Shapiro, Eiichiro Komatsu, Kyungjin Ahn, Garrelt MellemaAbstract:We calculate the angular power spectrum of the Cosmic Microwave Background (CMB) 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 (IGM). For the first time we take into account the "self-regulation" of Reionization: star formation in low-mass dwarf galaxies (10^8 M_\sun \lesssim M \lesssim 10^9 M_\sun) or minihalos (10^5 M_\sun \lesssim M \lesssim 10^8 M_\sun) 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 (\sim 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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Will nonlinear peculiar velocity and inhomogeneous Reionization spoil 21 cm cosmology from the epoch of Reionization
Physical review letters, 2013Co-Authors: Paul R. Shapiro, Ilian T. Iliev, Garrelt Mellema, Kyungjin Ahn, Yi Mao, Kanan K. Datta, Jun KodaAbstract:The 21 cm background from the epoch of Reionization is a promising cosmological probe: line-of-sight velocity fluctuations distort redshift, so brightness fluctuations in Fourier space depend upon angle, which linear theory shows can separate cosmological from astrophysical information. Nonlinear fluctuations in ionization, density, and velocity change this, however. The validity and accuracy of the separation scheme are tested here for the first time, by detailed Reionization simulations. The scheme works reasonably well early in Reionization (
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Simulating Reionization: Character and Observability.
2008Co-Authors: Ilian T. Iliev, Garrelt Mellema, Paul R. Shapiro, Ue-li Pen, Patrick Mcdonald, J. Richard BondAbstract: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 sufficiently large scales to derive the characteristic scales of the Reionization process and thus allowing for realistic observational predictions. Our group has recently performed the first such large-scale radiative transfer simulations of Reionization, run on top of state-of-the-art simulations of early structure formation. This allowed us to make the first realistic observational predictions about the Epoch of Reionization based on detailed radiative transfer and structure formation simulations. We discuss the basic features of Reionization derived from our simulations and some recent results on the observational implications for the high-redshift Ly-alpha sources.
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Dependence of the Local Reionization History on Halo Mass and Environment: Did Virgo Reionize the Local Group?
Monthly Notices of the Royal Astronomical Society, 2007Co-Authors: Simone M. Weinmann, Andrea V. Macciò, Ilian T. Iliev, Garrelt Mellema, Ben MooreAbstract:The Reionization of the Universe has profound effects on the way galaxies form and on their observed properties at later times. Of particular importance is the relative timing of the Reionization history of a region and its halo assembly history, which can affect the nature of the first stars formed in that region, the properties and radial distribution of its stellar halo, globular cluster population and its satellite galaxies. We distinguish two basic cases for the Reionization of a halo - internal Reionization, whereby the stars forming in situ reionize their host galaxy, and external Reionization, whereby the progenitor of a galaxy is reionized by external radiation before its own stars are able to form in sufficient numbers. We use a set of large-scale radiative transfer and structure formation simulations, based on cosmologies derived from both WMAP 1-year and WMAP 3-year data, to evaluate the mean Reionization redshifts and the probability of internal/external Reionization for Local Group-like systems, galaxies in the field and central cD galaxies in clusters. We find that these probabilities are strongly dependent on the underlying cosmology and the efficiency of photon production, but also on the halo mass. There is a rapid transition between predominantly external and predominantly internal Reionization at a mass scale of 1.0e12 Msun (corresponding roughly to L*galaxies), with haloes less massive than this being reionized preferentially from distant sources. We provide a fit for the Reionization redshift as a function of halo mass, which could be helpful to parameterize Reionization in semi-analytical models of galaxy formation on cosmological scales. We find no statistical correlation between the Reionization history of field galaxies and their environment.
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Self-regulated Reionization
Monthly Notices of the Royal Astronomical Society, 2007Co-Authors: Ilian T. Iliev, Garrelt Mellema, Paul R. Shapiro, Ue-li PenAbstract:Recently, we have presented the first, truly large-scale radiative transfer simulations of inhomogeneous cosmic Reionization which resolve all the possible halo sources down to the dwarf galaxy mass range, M ≥ 10 9 M⊙, in a comoving volume (100 h - 1 Mpc) 3 . This is large enough to sample the global mean history, geometry and statistical properties of Reionization fairly and accurately for the first time. Here we present new simulations which extend the source halo mass range downward to 10 8 M⊙, to capture the full range of halo masses thought to be primarily responsible for Reionization by their star formation following atomic hydrogen radiative cooling and gravitational collapse. Haloes below about 10 9 M⊙, however, are subject to Jeans-mass filtering in the ionized regions, which suppresses their baryonic content and their ability to release ionizing radiation. By including these smaller mass haloes but accounting for their suppression, too, we find that Reionization is 'self-regulating', as follows. As the mean ionized fraction rises, so does the fraction of the volume within which suppression occurs. Hence, the degree of suppression is related to the mean ionized fraction. Since low-mass haloes with high efficiency (i.e. high emissivity) achieve a given mean ionized fraction earlier than do those with low efficiency, Jeans-mass filtering compensates for the difference in the emissivity of the suppressible haloes in these two cases. As a result, in the presence of lower mass source haloes, Reionization begins earlier, but the later stages of Reionization and the time of overlap are dictated by the efficiency of the higher mass haloes, independent of the efficiency of the suppressible, lower mass haloes. Hence, while the lower mass haloes do not alter the overlap redshift, Z ov , they serve to boost the electron-scattering optical depth of the universe, τ es . This may explain why observations of quasar absorption spectra at high redshift find that Reionization ended late (Z ov 11). We present results for the Lambda cold dark matter universe with cosmological parameters from both 1- and 3-yr data releases of Wilkinson Microwave Anisotropy Probe. Reionization histories consistent with current constraints on Z ov and τ es are shown to be achievable with standard stellar sources in haloes above 10 8 M⊙. Neither minihaloes nor exotic sources are required, and the phenomenon of 'double Reionization' previously suggested does not occur.
