We model the high redshift (z > 5) Lyman-$α$ emitting (LAE) galaxy population using the empirical rest-frame equivalent width distribution. We calibrate to the observed luminosity function and angular correlation function at z = 5.7 as measured by the SILVERRUSH survey. This allows us to populate the high-dynamic-range Sherwood simulation suite with LAEs, and to calculate the transmission of their Ly $α$ emission through the inter-galactic medium (IGM). We use this simulated population to explore the effect of the IGM on high-redshift observations of LAEs, and make predictions for the narrowband filter redshifts at z = 6.6, 7.0 and 7.3. Comparing our model with existing observations, we find a late reionization is suggested, consistent with the recent low optical depth derived from the cosmic microwave background (CMB) by the Planck collaboration and the opacity fluctuations in the Ly $α$ forest. We also explore the role of the circum-galactic medium (CGM) and the larger volume of gas which is infalling onto the host halo versus the IGM in attenuating the Ly $α$ signal, finding that a significant fraction of the attenuation is due to the CGM and infalling gas, which increases towards the end of reionization, albeit with a large scatter across the mock LAE population.
We present an analysis of the evolution of the Lyman-series forest into the epoch of reionization using cosmological radiative transfer simulations in a scenario where reionization ends late. We explore models with different midpoints of reionization and gas temperatures. We find that once the simulations have been calibrated to match the mean flux of the observed Lyman-$α$ forest at $4 < z < 6$, they also naturally reproduce the distribution of effective optical depths of the Lyman-$β$ forest in this redshift range. We note that the tail of the largest optical depths that is most challenging …
We discuss the possible origin of the double-peaked profiles recently observed in Lyman-Alpha Emitters (LAEs) at the epoch of reionization ($z \gtrsim 6.5$) from obscured active galactic nuclei (AGN). Combining the extent of the Lyman-$α$ near-zones estimated from the blue peak velocity offset in these galaxies, with the ionizing emissivity of quasars at $z \gtrsim 6$, we forecast the intrinsic UV and X-ray luminosities of the AGN needed to give rise to their double-peaked profiles. We also estimate the extent of the obscuration of the AGN by comparing their luminosities to those of similar qu…
The fraction of ionizing photons escaping from galaxies, $f_{esc}$, is at the same time a crucial parameter in modelling reionization and a very poorly known quantity, especially at high redshift. Recent observations are starting to constrain the values of $f_{esc}$ in low-z star-forming galaxies, but the validity of this comparison remains to be verified. Applying at high-z the empirical relation between $f_{esc}$ and the UV slope trends derived from the Low-z Lyman Continuum Survey, we use the DELPHI semi-analytical galaxy formation model to estimate the global ionizing emissivity of high-z …
We study statistics of the 21-cm signal from the epoch of reionization. We propose to use [OIII] line emitting galaxies to cross-correlate with the 21-cm signal from $z = 7 - 10$. To this aim, we employ simulations of reionization obtained post-processing the high-resolution cosmological hydrodynamic simulation Massive Black-II with the three-dimensional (3D) radiative transfer code CRASH to follow the propagation of ionizing photons from a variety of sources. We show that, during the early phases of reionization, the 21-cm signal is positively correlated with the spatial distribution of the […
JWST ASPIRE: How Did Galaxies Complete Reionization? Evidence for Excess IGM Transmission around ${\rm [O\,{\scriptstyle III}]}$ Emitters during Reionization
The epoch of reionization (6 < z < 10) marks the period in our universe when the first large galaxies grew to fruition, and began to affect the universe around them. Massive stars, and potentially accreting supermassive black holes, filled the universe with ionizing radiation, burning off the haze of neutral gas that had filled the intergalactic medium (IGM) since recombination (z~1000). The evolution of this process constrains key properties of these earliest luminous sources, thus observationally constraining reionization is a key science goal for the next decade. The measurement of Lyman-al…
Stacking 21-cm Maps around Lyman-$α$ Emitters during Reionization: Prospects for a Cross-correlation Detection with the Hydrogen Epoch of Reionization Array
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…
The latest measurements of CMB electron scattering optical depth reported by Planck significantly reduces the allowed space of HI reionization models, pointing toward a later ending and/or less extended phase transition than previously believed. Reionization impulsively heats the intergalactic medium (IGM) to $\sim10^4$ K, and owing to long cooling and dynamical times in the diffuse gas, comparable to the Hubble time, memory of reionization heating is retained. Therefore, a late ending reionization has significant implications for the structure of the $z\sim5-6$ Lyman-$α$ (ly$α$) forest. Using…
Distant luminous Lyman-alpha emitters are excellent targets for detailed observations of galaxies in the epoch of reionisation. Spatially resolved observations of these galaxies allow us to simultaneously probe the emission from young stars, partially ionised gas in the interstellar medium and to constrain the properties of the surrounding hydrogen in the circumgalactic medium. We review recent results from (spectroscopic) follow-up studies of the rest-frame UV, Lyman-alpha and [CII] emission in luminous galaxies observed ~500 Myr after the Big Bang with ALMA, HST/WFC3 and VLT/X-SHOOTER. These…
We investigate Lyman-$α$ transmission spikes at $z > 5$ in synthetic quasar spectra, and discuss their connection to the properties of the intergalactic medium and their ability to constrain reionization models. We use state-of-the-art radiation-hydrodynamic simulations from the Cosmic Reionization On Computers series to predict the number of transmission spikes as a function of redshift, both in the ideal case of infinite spectral resolution and in a realistic observational setting. Transmission spikes are produced in highly-ionized underdense regions located in the vicinity of UV sources. We…
We probe what constraints for the global ionized hydrogen fraction the Void Probability Function (VPF) clustering can give for the Lyman-Alpha Galaxies in the Epoch of Reionization (LAGER) narrowband survey as a function of area. Neutral hydrogen acts like a fog for Lyman-alpha emission, and measuring the drop in the luminosity function of Lyman-$α$ emitters (LAEs) has been used to constrain the ionization fraction in narrowband surveys. However, the clustering of LAEs is independent from the luminosity function's inherent evolution, and can offer additional constraints for reionization under …
Reionization leads to large spatial fluctuations in the intergalactic temperature that can persist well after its completion. We study the imprints of such fluctuations on the $z\sim5$ Ly$α$ forest flux power spectrum using a set of radiation-hydrodynamic simulations that model different reionization scenarios. We find that large-scale coherent temperature fluctuations bring $\sim20-60\%$ extra power at $k\sim0.002$ s/km, with the largest enhancements in the models where reionization is extended or ends the latest. On smaller scales ($k\gtrsim0.1$ s/km), we find that temperature fluctuations s…
Galaxy Proximate Damped Lyman-Alpha Systems and HI Reionization Topology in TECHNICOLOR DAWN
New Mexico State University（新墨西哥州立大学）；Cosmic Dawn Center (DAWN)（宇宙黎明中心（DAWN））；Niels Bohr Institute, University of Copenhagen / DTU-Space Technical University of Denmark（哥本哈根大学尼尔斯·玻尔研究所/丹麦技术大学空间研究所）
The high redshift Lyman-alpha forest, in particular the Gunn-Peterson trough, is the most unambiguous signature of the neutral to ionized transition of the intergalactic medium (IGM) taking place during the Epoch of Reionization (EoR). Recent studies, e.g. Kulkarni et al. (2019a) and Keating et al. (2019), showed that reproducing the observed Lyman-alpha opacities after overlap required a non-monotonous evolution of cosmic emissivity: rising, peaking at z=6, and then decreasing onwards to z=4. Such an evolution is puzzling considering galaxy build-up and the cosmic star formation rate are stil…
Identifying low-redshift galaxies that emit Lyman Continuum radiation (LyC leakers) is one of the primary, indirect methods of studying galaxy formation in the epoch of reionization. However, not only has it proved challenging to identify such systems, it also remains uncertain whether the low-redshift LyC leakers are truly "analogues" of the sources that reionized the Universe. Here, we use high-resolution cosmological radiation hydrodynamics simulations to examine whether simulated galaxies in the epoch of reionization share similar emission line properties to observed LyC leakers at $z\sim3…
The time frame in which hydrogen reionization occurred is highly uncertain, but can be constrained by observations of Lyman-alpha (Ly$α$) emission from distant sources. Neutral hydrogen in the intergalactic medium (IGM) attenuates Ly$α$~photons emitted by galaxies. As reionization progressed the IGM opacity decreased, increasing Ly$α$~visibility. The galaxy Ly$α$~luminosity function (LF) is thus a useful tool to constrain the timeline of reionization. In this work, we model the Ly$α$~LF as a function of redshift, $z=5-10$, and average IGM neutral hydrogen fraction, $\overline{x}_\textsc{hi}$. …
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 Ly…
The spectral evolution of the first Galaxies. III. Simulated James Webb Space Telescope spectra of reionization-epoch galaxies with Lyman continuum leakage
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）
The origins of Lyman continuum (LyC) photons responsible for the reionization of the universe are as of yet unknown and highly contested. Detecting LyC photons from the epoch of reionization is not possible due to absorption by the intergalactic medium, which has prompted the development of several indirect diagnostics to infer the rate at which galaxies contribute LyC photons to reionize the universe by studying lower-redshift analogs. We present the Low-redshift Lyman Continuum Survey (LzLCS) comprising measurements made with HST/COS for a z=0.2-0.4 sample of 66 galaxies. After careful proce…
We present semi-analytical models of high redshift Lyman-α emitters (LAEs) in order to constrain the star formation efficiency in those galaxies. Our supernova feedback induced star formation model along with Sheth-Tormman halo mass function correctly reproduces the shape, amplitude and the redshift evolution of UV and Lyman-α luminosity functions of LAEs in the redshift range z = 2 to 7.3. We show that the fraction of Lyman-α emitting galaxies increases with increasing redshifts reaching to unity just after the reionisation. However, we show that star formation efficiency in those LAEs does n…
Identifying the mechanisms driving the escape of Lyman Continuum (LyC) photons is crucial to find Lyman Continuum Emitter (LCE) candidates. To understand the physical properties involved in the leakage of LyC photons, we investigate the connection between the HI covering fraction, HI velocity width, the Lyman alpha (LyA) properties and escape of LyC photons in a sample of 22 star-forming galaxies including 13 LCEs. We fit the stellar continua, dust attenuation, and absorption lines between 920 and 1300 A to extract the HI covering fractions and dust attenuation. Additionally, we measure the HI…
