We investigate the contribution of extended radio sources such as Centaurus A, and Galactic supernova remnants (SNRs) to our ability to detect the statistical $21\,\rm{cm}$ signal from the Epoch of Reionisation (EoR) with the Murchison Widefield Array (MWA). These sources are typically ignored because they are in highly attenuated parts of the MWA primary beam, however in aggregate these sources have apparent flux densities of $10\,\rm{Jy}$ on angular scales we expect to detect the $21\,\rm{cm}$ signal. We create bespoke multi-component 2D Gaussian models for Galactic SNRs and for Centaurus A, and simulate the visibilities for two MWA snapshot observations. We grid those visibilities and then Fourier transform them with respect to frequency, averaging them both spherically and cylindrically to produce the 1D and 2D power spectra. We compare the simulated 1D power spectra to the expected $21\,\rm{cm}$ power spectrum. We find that although these extended sources are in highly attenuated parts of the MWA primary beam pattern, collectively they have enough power ($\sim10^4-10^5\,\rm{mK^2}\,\it{h^{-3}} \,\rm{Mpc^{3}}$) on EoR significant modes ($|\mathbf{k}| \leq 0.1 h \rm{Mpc}^{-1}$) to prohibit detection of the $21\,\rm{cm}$ signal ($10^4\,\rm{mK^2}\,\it{h^{-3}} \,\rm{Mpc^{3}}$). We find that $50-90\%$ of sources must be removed in order to reduce leakage to a level of $10-20\%$ of the $21\,\rm{cm}$ power spectrum on EoR significant modes. The effects of widefield extended sources will have implications on the detectability of the $21\,\rm{cm}$ signal for the MWA and with the future Square Kilometre Array (SKA).
We assess the effect of a population of high-redshift quasars on the 21-cm power spectrum during the epoch of reionisation. Our approach is to implement a semi-numerical scheme to calculate the three-dimensional structure of ionised regions surrounding massive halos at high redshift. We include the ionising influence of luminous quasars by populating a simulated overdensity field with quasars using a Monte Carlo Markov Chain algorithm. We find that quasars modify both the amplitude and shape of the power spectrum at a level which is of the same order as the fractional contribution to reionisat…
Impact of anisotropic photon emission from sources during the epoch of reionisation
University of Sussex（萨塞克斯大学）；The Open University of Israel（以色列开放大学）；Stockholm University（斯德哥尔摩大学）；KTH Royal Institute of Technology（瑞典皇家理工学院）；University of Groningen（格罗宁根大学）
Characterising the epoch of reionisation using the cross-correlation of the kSZ effect and CMB lensing
University of Cambridge（剑桥大学）；Kavli Institute for Cosmology Cambridge（卡弗里宇宙学剑桥研究所）；School of Earth and Space exploration, Arizona State University（亚利桑那州立大学地球与太空探索学院）；Institute of Astronomy, University of Cambridge（剑桥大学天文学研究所）；Department of Physics, University of Oxford（牛津大学物理系）；Kavli Institute for Particle Astrophysics and Cosmology, Stanford University（斯坦福大学卡弗里粒子天体物理学与宇宙学研究所）；Department of Physics, Stanford University（斯坦福大学物理系）
Intergalactic medium temperature is a powerful probe of the epoch of reionisation, as information is retained long after reionisation itself. However, mean temperatures are highly degenerate with the timing of reionisation, with the amount heat injected during the epoch, and with the subsequent cooling rates. We post-process a suite of semi-analytic galaxy formation models to characterise how different thermal statistics of the intergalactic medium can be used to constrain reionisation. Temperature is highly correlated with redshift of reionisation for a period of time after the gas is heated.…
Reionisation blurring is a non-linear correction to the cosmic microwave background that acts similar to weak gravitational lensing and that can be computed from linear perturbations through a blurring potential. Its impact on the cosmic microwave background is roughly two order of magnitude smaller than that of lensing, in isolation. But the blurring potential is strongly correlated with the lensing potential thereby generating a potentially observable cross-correlation. We compute for the first time the inclusive impact of reionisation blurring on the temperature angular power spectrum and d…
Reionisation time field reconstruction from 21-cm Maps: Investigating predictor coherence in WDM cosmology
Université de Strasbourg（斯特拉斯堡大学）；CNRS UMR 7550, Observatoire Astronomique de Strasbourg（法国国家科学研究中心联合研究实验室7550号，斯特拉斯堡天文台）；Institut Pluridisciplinaire Hubert Curien (IPHC), Université de Strasbourg, CNRS/IN2P3（于贝尔·居里跨学科研究所，斯特拉斯堡大学，法国国家科学研究中心/法国国家核物理及粒子物理研究所）；Department of Astronomy, University of Texas at Austin（德克萨斯大学奥斯汀分校天文学系）；Université Paris Cité, CNRS(/IN2P3), Astroparticule et Cosmologie（巴黎西岱大学，法国国家科学研究中心（/法国国家核物理及粒子物理研究所），亚原子粒子与宇宙学）
Motivated by the current constraints on the epoch of reionisation from recent cosmic microwave background observations, ionising background measurements of star-forming galaxies, and low redshifts line-of-sight probes, we propose a new data-motivated parameterisation of the history of the average ionisation fraction. This parameterisation describes a flexible redshift-asymmetric reionisation process in two regimes that is capable of fitting all the current constraints.
We introduce the "Asymmetric Radiative Transfer In Shells Technique" (ARTIST), a new method for photon propagation on large scales that explicitly conserves photons, propagates photons at the speed of light, approximately accounts for photon directionality, and closely reproduces results of more detailed radiative transfer (RT) codes. Crucially, it is computationally fast enough to evolve the large cosmological volumes required to predict the 21cm power spectrum on scales that will be probed by future experiments targeting the Epoch of Reionisation (EoR). Most semi-numerical models aimed at pr…
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 quantify the presence of Lyα damping wing absorption from a partially-neutral intergalactic medium (IGM) in the spectrum of the $z=7.08$ QSO, ULASJ1120+0641. Using a Bayesian framework, we simultaneously account for uncertainties in: (i) the intrinsic QSO emission spectrum; and (ii) the distribution of cosmic HI patches during the epoch of reionisation (EoR). For (i) we use a new intrinsic Lyα emission line reconstruction method (Greig et al.), sampling a covariance matrix of emission line properties built from a large database of moderate-$z$ QSOs. For (ii), we use the Evolution of 21-cm S…
We apply Bayesian statistics to perform model selection on different reionisation scenarios via the Multinest algorithm. Initially, we recover the results shown by 21CMMC for the parameter estimation of 21cmFAST models. We proceed to test several toy models of the Epoch of Reionisation (EoR) defined in contrasting morphology and scale. We find that LOFAR observations are unlikely to allow model selection even with long integration times. HERA would require 61 dipoles to perform the same analysis in 1080 hours, and becomes comparable to the SKA with 217 dipoles. We find the SKA requires only 32…
Small galaxies are thought to be the main contributors to the ionising budget of the Universe before reionisation was complete. There have been a number of numerical studies trying to quantify their ionising efficiency through the escape fraction $f_{esc}$. While there is a clear trend that $f_{esc}$ is higher for smaller haloes, there is a large scatter in the distribution of $f_{esc}$ for a single halo mass. We propose that this is due to the intrinsic burstiness of star formation in low mass galaxies. We performed high resolution radiative hydrodynamics simulations with Ramses-RT to model t…
The cosmic 21 cm signal is set to revolutionise our understanding of the early Universe, allowing us to probe the 3D temperature and ionisation structure of the intergalactic medium (IGM). It will open a window onto the unseen first galaxies, showing us how their UV and X-ray photons drove the cosmic milestones of the epoch of reionisation (EoR) and epoch of heating (EoH). To facilitate parameter inference from the 21 cm signal, we previously developed 21CMMC: a Monte Carlo Markov Chain sampler of 3D EoR simulations. Here we extend 21CMMC to include simultaneous modelling of the EoH, resulting…
The role of higher order Lyman series photons on the 21cm absorption or emission signature of the IGM against the background CMB during the Epoch of Reionisation is examined. It is shown that, taking into account the diminishing resonance line scattering cross section with increasing Lyman order, a non-negligible net scattering rate of higher order Lyman photons is expected. The resulting radiative cascades will substantially enhance the number density of Lyman-alpha photons near a radiation source. It is also shown that the higher order Lyman series photons are able to collisionally heat the …
Detecting the cosmic 21-cm signal during the Epoch of Reionisation and Cosmic Dawn will reveal insights into the properties of the first galaxies and advance cosmological parameter estimation. Until recently, the primary focus for astrophysical parameter inference from the 21-cm signal centred on the power spectrum (PS). However, the cosmic 21-cm signal is highly non-Gaussian rendering the PS sub-optimal for characterising the cosmic signal. In this work, we introduce a new technique to analyse the non-Gaussian information in images of the 21-cm signal called the Wavelet Scattering Transform (…
Evidence repeatedly suggests that cosmological sheets, filaments and voids may be substantially magnetised today. The origin of magnetic fields in the intergalactic medium is however currently uncertain. We discuss a magnetogenesis mechanism based on the exchange of momentum between hard photons and electrons in an inhomogeneous intergalactic medium. Operating near ionising sources during the epoch of reionisation, it is capable of generating magnetic seeds of relevant strengths over scales comparable to the distance between ionising sources. Furthermore, when the contributions of all ionising…
The recent low value of Planck (2016) integrated optical depth to Thomson scattering suggests that the reionization occurred fairly suddenly, disfavoring extended reionization scenarios. This will have a significant impact on the 21cm power spectrum. Using a semi-numerical framework, we improve our model from Hassan et al. (2016) to include time-integrated ionisation and recombination effects, and find that this leads to more sudden reionisation. It also yields larger HII bubbles which leads to an order of magnitude more 21cm power on large scales, while suppressing the small scale ionization …
Interplanetary Scintillation (IPS) induces intensity fluctuations in small angular size astronomical radio sources via the distortive effects of spatially and temporally varying electron density associated with outflows from the Sun. These radio sources are a potential foreground contaminant signal for redshifted HI emission from the Epoch of Reionisation (EoR) because they yield time-dependent flux density variations in bright extragalactic point sources. Contamination from foreground continuum sources complicates efforts to discriminate the cosmological signal from other sources in the sky. …
Gravitational Lensing Effects by Galaxy Clusters on Ionised Bubble Size Distribution during the Epoch of Reionisation
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文学与空间科学学院）；Key Laboratory of Space Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台空间天文与技术重点实验室）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；State Key Laboratory of Radio Astronomy and Technology（射电天文与技术国家重点实验室）
Using a Bayesian framework, we quantify what current observations imply about the history of the epoch of reionisation (EoR). We use a popular, three-parameter EoR model, flexible enough to accommodate a wide range of physically-plausible reionisation histories. We study the impact of various EoR observations: (i) the optical depth to the CMB measured by Planck 2016; (ii) the dark fraction in the Lyman $α$ and $β$ forests; (iii) the redshift evolution of galactic Ly$α$ emission (so-called "Ly$α$ fraction"); (iv) the clustering of Ly$α$ emitters; (v) the IGM damping wing imprint in the spectrum…
One of the principal systematic constraints on the Epoch of Reionisation (EoR) experiment is the accuracy of the foreground calibration model. Recent results have shown that highly accurate models of extended foreground sources, and including models for sources in both the primary beam and its sidelobes, are necessary for reducing foreground power. To improve the accuracy of the source models for the EoR fields observed by the Murchison Widefield Array (MWA), we conducted the MWA Long Baseline Epoch of Reionisation Survey (LoBES). This survey consists of multi-frequency observations of the mai…
(Abridged) Noise considerations for experiments that aim to statistically estimate the 21 cm signal from high redshift neutral hydrogen during the Epoch of Reionisation (EoR) using interferometric data are typically computed assuming a tracked observation, where the telescope pointing centre and instrument phase centre are the same over the observation. Current low frequency interferometers use aperture arrays of fixed dipoles, which are steered electronically on the sky, and have different properties to mechanically-steered single apertures, such as reduced sensitivity away from zenith, and d…
The measurement of the brightness temperature fluctuations of neutral hydrogen 21 cm lines from the Epoch of Reionisation (EoR) is expected to be a powerful tool for revealing the reionisation process. We study the 21 cm cross-correlation with Cosmic Microwave Background (CMB) temperature anisotropies, focusing on the effect of the patchy reionisation. We calculate, up to second order, the angular power spectrum of the cross-correlation between 21 cm fluctuations and the CMB kinetic Sunyaev-Zel'dovich effect (kSZ) from the EoR, using an analytical reionisation model. We show that the kSZ and t…
SKA-Low simulations for a cosmic dawn/epoch of reionisation deep field
SKA Observatory（SKA天文台）；Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester（曼彻斯特大学物理与天文学学院乔德雷尔银行天体物理学中心）；Department of Physics and Astronomy, University of Pennsylvania（宾夕法尼亚大学物理与天文学系）；LUX, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université（巴黎天文台卢克斯实验室，PSL研究大学，法国国家科学研究中心，索邦大学）；Kapteyn Astronomical Institute, University of Groningen（格罗宁根大学卡普坦天文研究所）；INAF – Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Laboratoire de Physique de l’Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris（巴黎高等师范学校物理实验室，PSL大学，法国国家科学研究中心，索邦大学，巴黎大学）；International Centre for Radio Astronomy Research, Curtin University（科廷大学国际射电天文研究中心）；ARC Centre of Excellence for All-Sky Astrophysics in 3D（ARC三维全天体物理学卓越中心）
The Multi-frequency Angular Power Spectrum (MAPS) is an alternative to spherically-averaged power spectra, and computes local fluctuations in the angular power spectrum without need for line-of-sight spectral transform. To test different approaches to MAPS and treatment of the foreground contamination, and compare with the spherically-averaged power spectrum, and the single-frequency angular power spectrum. We apply the MAPS to 110~hours of data in $z=6.2-7.5$ obtained for the Murchison Widefield Array Epoch of Reionisation experiment to compute the statistical power of 21~cm brightness temper…
Measurement of redshifted 21-cm emission from neutral hydrogen promises to be the most effective method for studying the reionisation history of hydrogen and, indirectly, the first galaxies. These studies will be limited not by raw sensitivity to the signal, but rather, by bright foreground radiation from Galactic and extragalactic radio sources and the Galactic continuum. In addition, leakage due to gain errors and non-ideal feeds conspire to further contaminate low-frequency radio obsevations. This leakage leads to a portion of the complex linear polarisation signal finding its way into Stok…
Intensity mapping enables us to test cosmology and fundamental physics during the Epoch of Reionisation, with power spectra of line fluctuations probing a large range of scales and redshifts. Cosmological volumes of 21cm line fluctuations in general modified gravity scenarios are presented, where additional parameters are the initial condition parameter $α$ of matter perturbations and the scale-dependent modified gravity parameter $Y$ that measures deviations from General Relativity in the Poisson equation. For upcoming surveys like the SKA we forecast, using the power spectra derived from our…
Spectral features introduced by instrumental chromaticity of radio interferometers have the potential to negatively impact the ability to perform Epoch of Reionisation (EoR) and Cosmic Dawn (CD) science using the redshifted neutral hydrogen emission line from the early Universe. We describe instrument calibration choices that influence the spectral characteristics of the science data, and assess their impact on EoR statistical and tomographic experiments. Principally, we consider the intrinsic spectral response of the receiving antennas, embedded within a complete frequency-dependent primary b…
The redshifted 21cm line of neutral hydrogen (Hi), potentially observable at low radio frequencies (~50-200 MHz), is a promising probe of the physical conditions of the inter-galactic medium during Cosmic Dawn and the Epoch of Reionisation (EoR). The sky-averaged Hi signal is expected to be extremely weak (~100 mK) in comparison to the Galactic foreground emission (~$10^4$ K). Moreover, the sky-averaged spectra measured by ground-based instruments are affected by chromatic propagation effects (of the order of tens of Kelvins) originating in the ionosphere. We analyze data collected with the up…
On the unique evolutionary mechanisms of massive quiescent galaxies in the epoch of reionisation
Swinburne University of Technology（斯威本科技大学）；JWST Australia Data Centre [JADC], Swinburne Advanced Manufacturing and Design Centre [AMDC]（JWST澳大利亚数据中心，斯威本先进制造与设计中心）
We explore methods for robust estimation of the 21 cm signal from the Epoch of Reionisation (EoR). A Kernel Density Estimator (KDE) is introduced for measuring the spatial temperature fluctuation power spectrum from the EoR. The KDE estimates the underlying probability distribution function of fluctuations as a function of spatial scale, and contains different systematic biases and errors to the typical approach to estimating the fluctuation power spectrum. Extraction of histograms of visibilities allows moments analysis to be used to discriminate foregrounds from 21 cm signal and thermal nois…
We predict the 21-cm global signal and power spectra during the Epoch of Reionisation using the MERAXES semi-analytic galaxy formation and reionisation model, updated to include X-ray heating and thermal evolution of the intergalactic medium. Studying the formation and evolution of galaxies together with the reionisation of cosmic hydrogen using semi-analytic models (such as MERAXES) requires N-body simulations within large volumes and high mass resolutions. For this, we use a simulation of side-length $210~h^{-1}$ Mpc with $4320^3$ particles resolving dark matter haloes to masses of $5\times1…
We apply two methods to estimate the 21~cm bispectrum from data taken within the Epoch of Reionisation (EoR) project of the Murchison Widefield Array (MWA). Using data acquired with the Phase II compact array allows a direct bispectrum estimate to be undertaken on the multiple redundantly-spaced triangles of antenna tiles, as well as an estimate based on data gridded to the $uv$-plane. The direct and gridded bispectrum estimators are applied to 21 hours of high-band (167--197~MHz; $z$=6.2--7.5) data from the 2016 and 2017 observing seasons. Analytic predictions for the bispectrum bias and vari…
We extend 21CMMC, a Monte Carlo Markov Chain sampler of 3D reionisation simulations, to perform parameter estimation directly on 3D light-cones of the cosmic 21cm signal. This brings theoretical analysis closer to the tomographic 21-cm observations achievable with next generation interferometers like HERA and the SKA. Parameter recovery can therefore account for modes which evolve with redshift/frequency. Additionally, simulated data can be more easily corrupted to resemble real data. Using the light-cone version of 21CMMC, we quantify the biases in the recovered astrophysical parameters if we…
A consistent, physical, and analytical model for CMB observables of reionisation I. Derivation, constraining power, and detectability of the auto-spectra
We compute the spherically-averaged power spectrum from four seasons of data obtained for the Epoch of Reionisation (EoR) project observed with the Murchison Widefield Array (MWA). We measure the EoR power spectrum over $k= 0.07-3.0~h$Mpc$^{-1}$ at redshifts $z=6.5-8.7$. The largest aggregation of 110 hours on EoR0 high-band (3,340 observations), yields a lowest measurement of (43~mK)$^2$ = 1.8$\times$10$^3$ mK$^2$ at $k$=0.14~$h$Mpc$^{-1}$ and $z=6.5$ (2$σ$ thermal noise plus sample variance). Using the Real-Time System to calibrate and the CHIPS pipeline to estimate power spectra, we select …
Higher-order methods of radiative transfer in simulations of the epoch of reionisation: Pn versus M1
Observatoire Astronomique de Strasbourg, Universite de Strasbourg, CNRS UMR 7550（斯特拉斯堡天文台，斯特拉斯堡大学）；Institut de Recherche Mathématique Avancée (IRMA), University of Strasbourg（斯特拉斯堡大学高等数学研究所）；Direction du Numérique - Pôle CESAR, University of Strasbourg（斯特拉斯堡大学数字事务处-CESAR中心）
We study cross-correlations of the kinetic Sunyaev-Zel'dovich effect (kSZ) and 21 cm signals during the epoch of reionisation (EoR) to measure the effects of patchy reionisation. Since the kSZ effect is proportional to the line-of-sight velocity, the kSZ-21 cm cross correlation suffers from cancellation at small angular scales. We thus focus on the correlation between the kSZ-squared field (kSZ$^2$) and 21 cm signals. When the global ionisation fraction is low ($x_e\lesssim 0.7$), the kSZ$^2$ fluctuation is dominated by rare ionised bubbles which leads to an anti-correlation with the 21 cm sig…
The Cosmic Dawn and Epoch of Reionisation, during which collapsed structures produce the first ionising photons and proceed to reionise the intergalactic medium, span a large range in redshift (z~30-6) and time (t_{age} ~ 0.1-1.0~Gyr). Exploration of these epochs using the redshifted 21~cm emission line from neutral hydrogen is currently limited to statistical detection and estimation metrics (e.g., the power spectrum) due to the weakness of the signal. Brightness temperature fluctuations in the line-of-sight (LOS) dimension are probed by observing the emission line at different frequencies, a…
The 21-cm line fluctuations and the cosmic microwave background (CMB) are powerful probes of the epoch of reionisation of the universe. We study the potential of the cross-correlation between 21-cm line fluctuations and CMB anisotropy to obtain further constraints on the reionisation history. We compute analytically the 21-cm cross-correlation with the CMB temperature anisotropy and polarisation, and we calculate the signal-to-noise (SN) ratio for its detection with Planck together with LOFAR, MWA and SKA. We find, on the one hand, that the 21-cm cross-correlation signal with CMB polarisation …
Interferometry of the cosmic 21-cm signal is set to revolutionise our understanding of the Epoch of Reionisation (EoR) and the Cosmic Dawn (CD). The culmination of ongoing efforts will be the upcoming Square Kilometre Array (SKA), which will provide tomography of the 21-cm signal from the first billion years of our Universe. Using a galaxy formation model informed by high-$z$ luminosity functions, here we forecast the accuracy with which the first phase of SKA-low (SKA1-low) can constrain the properties of the unseen galaxies driving the astrophysics of the EoR and CD. We consider three observ…
Detecting the 21-cm hyperfine transition from neutral hydrogen in the intergalactic medium is our best probe for understanding the astrophysical processes driving the Epoch of Reionisation (EoR). The primary means for a detection of this 21-cm signal is through a statistical measurement of the spatial fluctuations using the 21-cm power spectrum (PS). However, the 21-cm signal is non-Gaussian meaning the PS, which only measures the Gaussian fluctuations, is sub-optimal for characterising all of the available information. The upcoming Square Kilometre Array (SKA) will perform a deep, 1000 hr obs…
Emulation of the Global (sky-averaged) 21-cm signal with neural networks has been shown to be an essential tool for physical signal modelling. In this paper we present globalemu, a Global 21-cm signal emulator that uses redshift as a character defining variable alongside a set of astrophysical parameters to estimate the signal brightness temperature. Combined with physically-motivated data pre-processing this makes for a reliable and fast emulator that is relatively insensitive to the network design. globalemu can emulate a high resolution signal in 1.3 ms in comparison to 133 ms, a factor of …
Semi-numeric methods have made it possible to efficiently model the epoch of reionisation (EoR). While most implementations involve a reduction to a simple three-parameter model, we introduce a new mass-dependent ionising efficiency parameter that folds in physical parameters that are constrained by the latest numerical simulations. This new parameterization enables the effective modeling of a broad range of host halo masses containing ionising sources, extending from the smallest Population III host halos with $M \sim 10^6 M_\odot$, which are often ignored, to the rarest cosmic peaks with $M …
The recent detection of ULASJ1342+0928, a bright QSO at $z=7.54$, provides a powerful probe of the ionisation state of the intervening intergalactic medium, potentially allowing us to set strong constraints on the epoch of reionisation (EoR). Here we quantify the presence of Ly$α$ damping wing absorption from the EoR in the spectrum of ULASJ1342+0928. Our Bayesian framework simultaneously accounts for uncertainties on: (i) the intrinsic QSO emission (obtained from reconstructing the Ly$α$ profile from a covariance matrix of emission lines) and (ii) the distribution of HII regions during reioni…
Recent results of ground-based telescopes, giving high-quality measurements of the CMB temperature power spectrum on small scales motivate the need for an accurate model of foregrounds, which dominate the primary signal at these multipoles. In a previous work, we have shown that cosmological information could be retrieved from the power spectrum of the thermal SZ effect. In this work, we introduce a physically motivated model of the Epoch of Reionisation in the cosmological analysis of CMB data, which is coherent on all scales. In particular, at high multipoles, the power spectrum of the kinet…
Using the latest upper limits on the 21-cm power spectrum at $z\approx9.1$ from the Low Frequency Array (LOFAR), we explore regions of parameter space which are inconsistent with the data. We use 21CMMC, a Monte Carlo Markov Chain sampler of 21cmFAST which directly forward models the 3D cosmic 21-cm signal in a fully Bayesian framework. We use the astrophysical parameterisation from 21cmFAST, which includes mass-dependent star formation rates and ionising escape fractions as well as soft-band X-ray luminosities to place limits on the properties of the high-$z$ galaxies. Further, we connect the…
Line intensity mapping opens up a new and exciting window for probing cosmology and fundamental physics during the Epoch of Reionisation, extending to redshifts previously untested by galaxy surveys. The power spectra of these line fluctuations are a promising tool to test gravity over a large range of scales and redshifts. We simulate cosmological volumes of 21cm fluctuations in general parametrisations of modified gravity, in order to calculate the corresponding power spectra, where additional parameters are the initial condition of matter perturbations $α$ and the scale-dependent modified g…
Globular clusters are dense stellar systems that have typical ages of ~13 billion years, implying that they formed at redshifts of z>~6. Massive stars in newly formed or primordial globular clusters could have played an important role during the epoch of cosmological reionisation (z>~6) as sources of energetic, neutral hydrogen ionising UV photons. We investigate whether or not these stars could have been as important in death as sources of energetic X-ray photons as they were during their main sequence lives. Most massive stars are expected to form in binaries, and an appreciable fraction of …
