Experiments designed to measure the redshifted 21~cm line from the Epoch of Reionization (EoR) are challenged by strong astrophysical foreground contamination, ionospheric distortions, complex instrumental response and other different types of noise (e.g. radio frequency interference). The astrophysical foregrounds are dominated by diffuse synchrotron emission from our Galaxy. Here we present a simulation of the Galactic emission used as a foreground module for the LOFAR- EoR key science project end-to-end simulations. The simulation produces total and polarized intensity over $10^\circ \times 10^\circ$ maps of the Galactic synchrotron and free-free emission, including all observed characteristics of the emission: spatial fluctuations of amplitude and spectral index of the synchrotron emission, together with Faraday rotation effects. The importance of these simulations arise from the fact that the Galactic polarized emission could behave in a manner similar to the EoR signal along the frequency direction. As a consequence, an improper instrumental calibration will give rise to leakages of the polarized to the total signal and mask the desired EoR signal. In this paper we address this for the first time through realistic simulations.
Intensity mapping of the HI 21 cm line and the CO 2.61 mm line from the epoch of reionization has emerged as powerful, complementary, probes of the high-redshift Universe. However, both maps and their cross-correlation are dominated by foregrounds. We propose a new analysis by which the signal is unbiased by foregrounds, i.e. it can be measured without foreground mitigation. We construct the antisymmetric part of the HI-CO cross-correlation, arising because the statistical fluctuations of two fields have different evolution in time. We show that the sign of this new signal can distinguish mode…
Intensity mapping of the H I 21 cm line and the CO 2.61 mm line from the epoch of reionization has emerged as powerful, complementary, probes of the high-redshift Universe. However, both maps and their cross-correlation are dominated by foregrounds. We propose a new analysis by which the signal is unbiased by foregrounds, i.e. it can be measured without foreground mitigation. We construct the antisymmetric part of two-point cross-correlation between intensity maps of the H I 21 cm line and the CO 2.61 mm line, arising because the statistical fluctuations of two fields have different evolution …
The cross-correlation between fluctuations in the electron scattering optical depth $τ_{\rm es}$ as probed by future Cosmic Microwave Background (CMB) experiments, and fluctuations in the 21cm differential brightness temperature $ΔT_{\rm 21cm}$ as probed by ground-based radio interferometers, will trace the reionization history of the Universe. In particular, the $τ_{\rm es}-$21cm cross-correlation should yield a determination of the characteristic bubble size distribution and ionization fraction as a function of redshift. When assuming that the cross-correlation signal is limited by instrumen…
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 low-frequency radio sky is dominated by the diffuse synchrotron emission of our Galaxy and extragalactic radio sources related to Active Galactic Nuclei and star-forming galaxies. This foreground emission is much brighter than the cosmological 21 cm emission from the Cosmic Dawn and Epoch of Reionization. Studying the physical properties of the foregrounds is therefore of fundamental importance for their mitigation in the cosmological 21 cm experiments. This chapter gives a comprehensive overview of the foregrounds and our current state-of-the-art knowledge about their mitigation.
Upcoming cosmic microwave background (CMB) surveys will soon make the first detection of the polarized Sunyaev-Zel'dovich effect, the linear polarization generated by the scattering of CMB photons on the free electrons present in collapsed objects. Measurement of this polarization along with knowledge of the electron density of the objects allows a determination of the quadrupolar temperature anisotropy of the CMB as viewed from the space-time location of the objects. Maps of these remote temperature quadrupoles have several cosmological applications. Here we propose a new application: reconst…
Context: Currently, detection of the primordial gravitational waves by the B-mode of Cosmic Microwave Background (CMB) is primarily limited by our knowledge of the polarized microwave foreground emissions. Thus improvements of the foreground analysis are necessary. As revealed in~\cite{2018arXiv180410382L}, the E-mode and B-mode of the polarized foreground have noticeable different properties, both in morphology and frequency spectrum, suggesting that they arise from different physical processes, and need to be studied separately. Aims: I will study the polarized emission from Galactic loops, …
$Ab$ $initio$ modeling of Galactic dust polarized CMB foreground
Nanjing University（南京大学）；University of California, San Diego（加州大学圣迭戈分校）；Kavli Institute for Theoretical Physics, University of California, Santa Barbara（加州大学圣巴巴拉分校卡弗里理论物理研究所）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）
We present 3D models of the Galactic magnetic field including regular and turbulent components, and of the distribution of matter in the Galaxy including relativistic electrons and dust grains. By integrating along the line of sight, we construct maps of the polarized Galactic synchrotron and thermal dust emissions for each of these models. We perform a likelihood analysis to compare the maps of the Ka, Q, V and W bands of the Wilkinson Microwave Anisotropy Probe (Wmap) and the 353 GHz Archeops data to the models obtained by varying the pitch angle of the regular magnetic field, the relative a…
Polarized Galactic synchrotron emission is an undesirable foreground for cosmic microwave background (CMB) experiments observing at frequencies $< 150$ GHz. We perform a combined analysis of observational data at 1.4, 2.3, 23, 30 and 33 GHz to quantify the spatial variation of the polarized synchrotron spectral index, $β^{pol}$, on $\sim3.5^\circ$ scales. We compare results from different data combinations to address limitations and inconsistencies present in these public data, and form a composite map of $β^{pol}$. Data quality masking leaves 44% sky coverage (73% for $|b|> 45^\circ$). Genera…
We produce simulations of emission of the atomic CII line in large sky fields in order to determine the current prospects for mapping this line during the high redshift Epoch of Reionization. We estimate the CII line intensity, redshift evolution and spatial fluctuations using observational relations between CII emission and the SFR in a galaxy for the frequency range of 200 GHz to 300 GHz. We obtained a frequency averaged intensity of CII emission of ${\rm I_{\rm CII}=(4 \pm 2)\times10^{2}\, Jy\, \rm sr^{-1}}$ in the redshift range $z\, \sim\, 5.3\, -\, 8.5$. Observations of CII emission in t…
We report the first direct and robust measurement of the faint-end slope of the Lyman-alpha emitter (LAE) luminosity function at z = 5.7. Candidate LAEs from a low-spectral-resolution blind search with IMACS on Magellan-Baade were targeted at higher resolution to distinguish high redshift LAEs from foreground galaxies. All but 2 of our 42 single-emission-line systems have flux F $< 2.0 \times 10^{-17}$ ergs s$^{-1}$ cm$^{-2}$, making these the faintest emission-lines observed for a z = 5.7 sample with known completeness, an essential property for determining the faint end slope of the LAE lumi…
We investigate the cross-correlation between the spatial distribution of Lyman Break Galaxies (LBGs) and the 21cm intensity mapping signal at $z\sim[3-5]$. At these redshifts, galactic feedback is supposed to only marginally affect the matter power spectrum, and the neutral hydrogen distribution is independently constrained by quasar spectra. Using a high resolution N-body simulation, populated with neutral hydrogen a posteriori, we forecast for the expected LBG-21cm cross-spectrum and its error for a 21cm field observed by the Square Kilometre Array (SKA1-LOW and SKA1-MID), combined with a sp…
Precise measurement of the foreground synchrotron emission, which contaminates the faint polarized cosmic microwave background radiation (CMB), is a major challenge for the next-generation of CMB experiments. To address this, dedicated foreground measurement experiments are being undertaken at radio frequencies between 2 and 40 GHz. Foreground polarized synchrotron emission measurements are particularly challenging, primarily due to the complicated frequency dependence in the presence of Faraday rotation, and are best recovered through broad fractional-bandwidth polarization measurements at fr…
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 …
Contribution to the 2026 Cosmology session of the 60th Rencontres de Moriond: Galactic moments: Understanding polarized foregrounds complexity in the quest for CMB primordial $B$ modes with LiteBIRD
Univ Toulouse, CNES, CNRS, IRAP（图卢兹大学，法国国家空间研究中心，法国国家科学研究中心，天体物理研究所）；Université Paris-Saclay, CNRS/IN2P3, IJCLab（巴黎-萨克雷大学，法国国家科学研究中心/法国国家粒子物理研究所，IJCLab）；Instituto de Astrofísica de Canarias（加那利群岛天体物理研究所）；Departamento de Astrofísica, Universidad de La Laguna (ULL)（拉帕拉塔大学天体物理学系）；Department of Physics, University of Oxford（牛津大学物理系）
A wealth of new data from upgraded and new radio interferometers are rapidly improving and transforming our understanding of the faint extra-galactic radio sky. Indeed the mounting statistics at sub-mJy and uJy flux levels is finally allowing us to get stringent observational constraints on the faint radio population and on the modeling of its the various components. In this paper I will provide a brief overview of the latest results in areas that are potentially important for an accurate treatment of extra-galactic foregrounds in experiments designed to probe the Epoch of Reionization.
