A Projected Estimate of the Reionization Optical Depth Using the CLASS Experiment's Sample-Variance Limited E-Mode Measurement
Duncan J. Watts, Bingjie Wang, Aamir Ali, John W. Appel, Charles L. Bennett, David T. Chuss, Sumit Dahal, Joseph R. Eimer, Thomas Essinger-Hileman, Kathleen Har… 展开作者
Duncan J. Watts, Bingjie Wang, Aamir Ali, John W. Appel, Charles L. Bennett, David T. Chuss, Sumit Dahal, Joseph R. Eimer, Thomas Essinger-Hileman, Kathleen Harrington, Gary Hinshaw, Jeffrey Iuliano, Tobias A. Marriage, Nathan J. Miller, Ivan L. Padilla, Lucas Parker, Matthew Petroff, Karwan Rostem, Edward J. Wollack, Zhilei Xu
We analyze simulated maps of the Cosmology Large Angular Scale Surveyor (CLASS) experiment and recover a nearly cosmic-variance limited estimate of the reionization optical depth $τ$. We use a power spectrum-based likelihood to simultaneously clean foregrounds and estimate cosmological parameters in multipole space. Using software specifically designed to constrain $τ$, the amplitude of scalar fluctuations $A_s$, and the tensor-to-scalar ratio $r$, we demonstrate that the CLASS experiment will be able to estimate $τ$ within a factor of two of the full-sky cosmic variance limit allowed by cosmic microwave background polarization measurements. Additionally, we discuss the role of CLASS's $τ$ constraint in conjunction with gravitational lensing of the CMB on obtaining a $\gtrsim4σ$ measurement of the sum of the neutrino masses.
CMB full-sky temperature data show a hemispherical asymmetry in power nearly aligned with the Ecliptic. In real space, this anomaly can be quantified by the temperature variance in the northern and southern Ecliptic hemispheres, with the north displaying an anomalously low variance while the south appears consistent with expectations from the best-fitting theory, LCDM. While this is a well-established result in temperature, the low signal-to-noise ratio in current polarization data prevents a similar comparison. Even though temperature and polarization are correlated, polarization realizations…
The End of Helium Reionization at z~2.7 Inferred from Cosmic Variance in HST/COS HeII Lyman Alpha Absorption Spectra
本文报道了在两个z~3类星体的HST/COS光谱中探测到的强烈变化的星系际HeII吸收。从我们对这些和三个档案视线中的HeII吸收的均匀分析中，我们发现平均HeII有效光学深度从z~2.3处的τ ~1显著增加到z~3.2处的τ>5，但在2.7< z <3处的2<τ <5的大散射在~10 Mpc的尺度上。这种分散主要是由于HeII部分和HeII电离背景的波动，而不是密度变化，探测的同时代HI森林。HeII吸收的半解析模型需要HeII电离背景的强烈降低来解释在z>2.7时吸收的强烈增加，这可能表明HeII再电离在z>2.7时是不完全的。同样，最近的三维数值模拟的HeII再电离定性地同意观察到的趋势，只有当HeII再电离完成在z=2.7或甚至更低，如我们的五个视线中的两个在z<2.8的大tau>3所示。通过在2.7< z <3时将样本大小加倍，我们新发现的HeII视线首次探测了氦完全电离时第二次再电离时期的多样性。
We study the spherically averaged bispectrum of the 21-cm signal from the Epoch of Reionization (EoR). This metric provides a quantitative measurement of the level of non-Gaussianity of the signal which is expected to be high. We focus on the impact of the light-cone effect on the bispectrum and its detectability with the future SKA-Low telescope. Our investigation is based on a single reionization light-cone model and an ensemble of 50 realisations of the 21-cm signal to estimate the cosmic variance errors. We calculate the bispectrum with a new, optimised direct estimation method, DviSukta w…
Current best limits on the 21-cm signal during reionization are provided at large scales ($\gtrsim$100 Mpc). To model these scales, enormous simulation volumes are required which are computationally expensive. We find that the primary source of uncertainty at these large scales is sample variance, which decides the minimum size of simulations required to analyse current and upcoming observations. In large-scale structure simulations, the method of `fixing' the initial conditions (ICs) to exactly follow the initial power spectrum and `pairing' two simulations with exactly out-of-phase ICs has b…
A number of independent observations suggest that the intergalactic medium was significantly neutral at $z=7$ and that reionization was, perhaps, still in progress at $z=5.7$. The narrowband survey, SILVERRUSH, has mapped over $2,000$ Lyman-$α$ emitters (LAEs) at these redshifts. Previous analyses have assumed that reionization was over by $z=5.7$, but this data may actually sample the final stages of reionization when the last neutral islands were relegated to the cosmic voids. Motivated by these developments, we reexamine LAE void and peak statistics and their ability to constrain reionizati…
Observation of redshifted 21-cm signals from neutral hydrogen holds the key to understanding the structure formation and its evolution during the reionization and post-reionization era. Apart from the presence of orders of magnitude larger foregrounds in the observed frequency range, the instrumental effects of the interferometers combined with the ionospheric effects present a considerable challenge in the extraction of 21-cm signals from strong foregrounds. The systematic effects of time and frequency correlated residual gain errors originating from the measurement process introduce a bias a…
We present the first application of the isosceles bispectrum to MCMC parameter inference from the cosmic 21-cm signal. We extend the MCMC sampler 21cmMC to use the fast bispectrum code, BiFFT, when computing the likelihood. We create mock 1000h observations with SKA1-low, using PyObs21 to account for uv-sampling and thermal noise. Assuming the spin temperature is much higher than that of the CMB, we consider two different reionization histories for our mock observations: fiducial and late-reionization. For both models we find that bias on the inferred parameter means and 1-$σ$ credible interva…
Cosmic Reionization imprints its signature on the temperature and polarization anisotropies of the cosmic microwave background (CMB). Advances in CMB telescopes have already placed a significant constraint on the history of reionization. As near-future CMB telescopes target the maximum sensitivity, or observations limited only by the cosmic variance (CV), we hereby forecast the potential of future CMB observations in constraining the history of reionization. In this study, we perform Markov Chain Monte Carlo analysis for CV-limited E-mode polarization observations such as the LiteBIRD (Light s…
This work presents an analytical approach for studying the cosmological 21cm background signal from the Dark Ages (DA) and subsequent Epoch of Reionization (EoR). We simulate differential observations of a galaxy cluster to demonstrate how these epochs can be studied with a specific form of the Sunyaev-Zel'dovich Effect called the SZE-21cm. This work produces simulated maps of the SZE-21cm and shows that the SZE-21cm can be extracted from future observations with low-frequency radio interferometers such as the Hydrogen Epoch of Reionization Array (HERA) and the Square Kilometre Array (SKA). In…
Calibration requirements for Epoch of Reionization 21-cm signal observations -- IV. Bias and variance with time and frequency correlated residual gains
Hemispherical power asymmetry has emerged as a new challenge to cosmology in early universe. While the cosmic microwave background (CMB) measurements indicated the asymmetry amplitude $A \simeq 0.07$ at the CMB scale $k_{\rm CMB}\simeq 0.0045\,{\rm Mpc}^{-1}$, the high-redshift quasar observations found no significant deviation from statistical isotropy. This conflict can be reconciled in some scale-dependent asymmetry models. We put forward a new parameterization of scale-dependent asymmetric power spectrum, inspired by a multi-speed inflation model. The 21-cm power spectrum from the epoch of…
21cm-line bispectrum as method to probe Cosmic Dawn and Epoch of Reionization
红移21 cm信号是研究宇宙黎明期和再电离期星系际介质状态的有效工具。在我们之前的工作中（Shimabukuro et al 2015），我们研究了方差和偏度，以给出21 cm功率谱的清晰解释，并发现偏度是X射线加热变得有效的时期的良好指标。因此，21厘米信号的空间分布的非高斯特征有望用于研究CD和EoR中的天体物理效应。在本文中，为了更详细地研究这种非高斯特征，我们专注于21厘米信号的双谱。21 cm亮温双谱可能是由于Wouthysen-Field（WF）效应、X射线加热和再电离等多种天体物理效应引起的非高斯性而产生的。我们研究了21厘米双谱的各种性质，如尺度依赖性、形状依赖性和红移演化。并研究了21 cm双谱各分量的贡献。我们发现，各分量的贡献具有典型的尺度依赖特征，在未来的实验中，我们可以利用21 cm双谱，结合功率谱和偏度，获得更详细的CD和EoR中IGM的信息。
Upcoming measurements of the high-redshift 21 cm signal from the Epoch of Reionization (EoR) are a promising probe of the astrophysics of the first galaxies and of cosmological parameters. In particular, the optical depth $τ$ to the last scattering surface of the cosmic microwave background (CMB) should be tightly constrained by direct measurements of the neutral hydrogen state at high redshift. A robust measurement of $τ$ from 21 cm data would help eliminate it as a nuisance parameter from CMB estimates of cosmological parameters. Previous proposals for extracting $τ$ from future 21 cm datase…
Measurements of the Epoch of Reionization (EoR) 21-cm signal hold the potential to constrain models of reionization. In this paper we consider a reionization model with three astrophysical parameters namely (1) the minimum halo mass which can host ionizing sources, $M_{\rm min}$, (2) the number of ionizing photons escaping into the IGM per baryon within the halo, $N_{\rm ion}$ and (3) the mean free path of the ionizing photons within the IGM, $R_{\rm mfp}$. We predict the accuracy with which these parameters can be measured from future observations of the 21-cm power spectrum (PS) using the up…
The epoch of reionization is one of the major phase transitions in the history of the universe, and is a focus of ongoing and upcoming cosmic microwave background (CMB) experiments with improved sensitivity to small-scale fluctuations. Reionization also represents a significant contaminant to CMB-derived cosmological parameter constraints, due to the degeneracy between the Thomson-scattering optical depth, $τ$, and the amplitude of scalar perturbations, $A_s$. This degeneracy subsequently hinders the ability of large-scale structure data to constrain the sum of the neutrino masses, a major tar…
The first generation (Pop-III) stars can ionize 1-10% of the universe by $z=15$, when the metal-enriched (Pop-II) stars may contribute negligibly to the ionization. This low ionization tail might leave detectable imprints on the large-scale CMB E-mode polarization. However, we show that physical models for reionization are unlikely to be sufficiently extended to detect any parameter beyond the total optical depth through reionization. This result is driven in part by the total optical depth inferred by Planck, indicating a reionization midpoint around $z=8$, which in combination with the requi…
Cosmic Microwave Background temperature and polarization anisotropies from Planck have estimated a lower value of the optical depth to reionization ($τ$) compared to WMAP. A significant period in the reionization history would then fall within $6<z< 10$, where detection of galaxies with Hubble Frontier Fields program and independent estimation of neutral hydrogen in the inter galactic medium by Lyman-$α$ observations are also available. This overlap allows an analysis of cosmic reionization which utilizes a direct combination of CMB and these astrophysical measurements and potentially breaks d…
The reionization optical depth is the most poorly determined of the six $Λ$CDM parameters fit to CMB anisotropy data. Instrumental noise and systematics have prevented uncertainties from reaching their cosmic variance limit. At present, the datasets providing the most statistical constraining power are the WMAP, Planck LFI, and Planck HFI full-sky polarization maps. As the reprocessed HFI data with reduced systematics are not yet publicly unavailable, we examine determinations of $τ$ using 9-year WMAP and 2015 Planck LFI data, with an emphasis on characterizing potential systematic bias result…
TORRCH: Tomographic reconstruction of the reionization of cosmic hydrogen with Ly$α$ emitters and non-Ly$α$-selected galaxies
Tata Institute of Fundamental Research（塔塔基础研究所）；IIT Kanpur（坎普尔印度理工学院）；KU Leuven（荷语鲁汶大学）；Istituto Nazionale di Astrofisica -Osservatorio Astronomico di Trieste（意大利国家天体物理研究所-的里雅斯特天文台）；SISSA International School for Advanced Studies（国际高等研究院）；INFN - Sezione di Trieste（意大利国家核物理研究所-的里雅斯特分部）；IFPU, Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）；ICSC - Centro Nazionale di Ricerca in High Performance Computing, Big Data e Quantum Computing（高性能计算、大数据与量子计算国家研究中心）；Kavli Institute for Cosmology and Institute of Astronomy（卡弗里宇宙学研究所和天文学研究所）；University of Nottingham（诺丁汉大学）；Institute for Astronomy, University of Edinburgh（爱丁堡大学天文学研究所）
Analysing the 21cm signal from the Epoch of Reionization with artificial neural networks
再电离时代的21厘米信号应在未来十年内观测到。虽然SKA寻路器预计会进行简单的统计检测，但SKA有望产生信号的完整3D映射。为了从观测数据中提取对描述基本天体物理过程的参数的限制，必须开发反演方法。例如，马尔可夫链蒙特卡罗方法已成功应用。在这里，我们测试另一种可能的反演方法：人工神经网络（ANN）。我们生成了一个由70个个体样本组成的训练集。每个样本都是由21 cm Fast代码产生的不同红移的21 cm功率谱加上描述天体物理过程的半数值模拟中使用的三个参数的值组成。使用这个集合，我们训练网络，以最小化它作为输出产生的参数值与真实值之间的误差。我们探讨了网络架构对培训质量的影响。然后，我们在新的54个测试样本集上测试训练好的网络，这些样本具有不同的参数值。我们发现，参数重建的质量取决于在一个给定的红移，包括热噪声和样本方差的不同参数的功率谱的灵敏度降低了重建的质量，并使用在几个红移的功率谱作为输入到人工神经网络提高了重建的质量。我们的结论是，人工神经网络是一个可行的反演方法，其主要优势是，他们需要一个稀疏的参数空间的探索，因此应该是可用的完整的数值模拟。
One of the most exciting advances of the current generation of telescopes has been the detection of galaxies during the epoch of reionization, using deep fields that have pushed these instruments to their limits. It is essential to optimize our analyses of these fields in order to extract as much information as possible from them. In particular, standard methods of measuring the galaxy luminosity function discard information on large-scale dark matter density fluctuations, even though this large-scale structure drives galaxy formation and reionization during the Cosmic Dawn. Measuring these de…
Detecting neutral hydrogen structures in the intergalactic medium (IGM) during cosmic reionization via absorption (21 cm forest) against a background radiation is considered independent and complementary to the three-dimensional tomography and power spectrum techniques. The direct detection of this absorption requires very bright ($\gtrsim 10$-100 mJy) background sources at high redshifts ($z\gtrsim 8$), which are evidently rare; very long times of integration; or instruments of very high sensitivity. This motivates a statistical one-dimensional (1D) power spectrum approach along narrow sightl…
Measurements of the one-point probability distribution function and higher-order moments (variance, skewness, and kurtosis) of the high-redshift 21 cm fluctuations are among the most direct statistical probes of the non-Gaussian nature of structure formation and evolution during reionization. However, contamination from astrophysical foregrounds and instrument systematics pose significant challenges in measuring these statistics in real observations. In this work, we use forward modelling to investigate the feasibility of measuring 21 cm one-point statistics through a foreground avoidance stra…
We establish a robust statistical description of the star-forming galaxy population at the end of cosmic HI reionization ($5.0\le{}z\le6.6$) from a large sample of 52 galaxies with spectroscopically confirmed redshifts from the VIMOS UltraDeep Survey. We identify galaxies with Ly$α$ either in absorption or in emission, at variance with most spectroscopic samples in the literature where Ly$α$ emitters dominate. We find that star-forming galaxies at these redshifts are distributed along a main sequence in the stellar mass vs. SFR plane. We report a flat evolution of the sSFR(z) in 3<z<6 compared…
Ringing of the Reionization: A first direct measurement of the intergalactic pressure smoothing scale at redshift z>4.2 as imprinted onto small-scale peculiar velocities in the Lyman-alpha forest
University of Hertfordshire（赫特福德大学）；Kavli Institute for Cosmology, University of Cambridge（剑桥大学卡弗里宇宙学研究所）；SISSA- International School for Advanced Studies（国际高等研究学院）；INFN – National Institute for Nuclear Physics（意大利国家核物理研究所）；IFPU, Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）；INAF, Osservatorio Astronomico di Trieste（的里雅斯特天文台）；ICSC - Centro Nazionale di Ricerca in High Performance Computing, Big Data e Quantum Computing（高性能计算、大数据与量子计算国家研究中心）；Institute of Astronomy, University of Cambridge（剑桥大学天文学研究所）
Cosmological measurements of the 21-cm line of neutral hydrogen are poised to dramatically enhance our understanding of the early universe. In particular, both the epochs of reionization and cosmic dawn remain largely uncharted, and the 21-cm signal is one of the few probes to reach them. The simplest 21-cm measurement is the global signal (GS), which corresponds to the averaged absorption or emission of 21-cm photons across the entire sky. While bright radio foregrounds swamp the cosmic signal over the entire frequency range observable, presenting a formidable hurdle, they can in principle be…
