The detection of primordial B-mode polarization is still challenging due to the relatively low amplitude compared to the galactic foregrounds. To remove the contribution from the foreground, a comprehensive picture of the galactic magnetic field is indispensable. The Velocity Gradient Technique (VGT) is promising in tracing magnetic fields based on the modern understanding of the magneto-hydrodynamic turbulence. In this work, we apply VGT to a HI region containing an intermediate velocity cloud and a local velocity cloud, which are distinguishable in position-position-velocity space. We show that VGT gives an excellent agreement with the Planck polarization and stellar polarization. We confirm the advantages of VGT in constructing the 3D galactic magnetic field.
The detailed structure of the Galactic bulge still remain uncertain. The strong difficulties of obtaining observations of stars in the Galactic bulge have hindered the acquisition of a kinematic representation for the inner kpc of the Milky Way. The observation of the 3-d kinematics in several low foreground extinction windows can solve this problem. We have developed a new technique, which combines precise stellar HST positions and proper motions with integral field spectroscopy, in order to obtain reliable 3-d stellar kinematics in crowded fields of the Galactic center. In addition, we prese…
A significant number of the parameters of a gamma-ray burst (GRB) and its host galaxy are calculated from the afterglow. There are various methods obtaining extinction values for the necessary correction for galactic foreground. These are: galaxy counts, from HI 21 cm surveys, from spectroscopic measurements and colors of nearby Galactic stars, or using extinction maps calculated from infrared surveys towards the GRB. We demonstrate that AKARI Far-Infrared Surveyor sky surface brightness maps are useful uncovering the fine structure of the galactic foreground of GRBs. Galactic cirrus structure…
The CMB polarization promises to unveil the dawn of time measuring the gravitational wave background emitted by the Inflation. The CMB signal is faint, however, and easily contaminated by the Galactic foreground emission, accurate measurements of which are thus crucial to make CMB observations successful. We review the CMB polarization properties and the current knowledge on the Galactic synchrotron emission, which dominates the foregrounds budget at low frequency. We then focus on the S-Band Polarization All Sky Survey (S-PASS), a recently completed survey of the entire southern sky designed …
Recent Planck observations of dust polarization in the Galaxy have revealed that the power in $E$ mode is twice that in $B$ mode. Caldwell et. al. have formulated a theoretical model in the context of magnetohydrodynamic (MHD) turbulence and found it problematic to account for this result. In particular, they concluded that there is a very narrow range of theoretical parameters that could account for the observation. This poses a problem of whether the accepted description of MHD turbulence can apply to the interstellar medium. We revisit the problem and demonstrate that MHD turbulence corresp…
Present day cosmic microwave background (CMB) studies require more accurate removal of Galactic foreground emission. In this paper, we consider a way of filtering out the diffuse Galactic fluctuations on the basis of their statistical properties, namely, the power-law spectra of fluctuations. We focus on the statistical properties of two major Galactic foregrounds that arise from magnetized turbulence, namely, diffuse synchrotron emission and thermal emission from dust and describe how their power laws change with the Galactic latitude. We attribute this change to the change of the geometry of…
The afterglow of a gamma ray burst (GRB) can give us valuable insight into the properties of its host galaxy. To correctly interpret the spectra of the afterglow we need to have a good understanding of the foreground interstellar medium (ISM) in our own Galaxy. The common practice to correct for the foreground is to use neutral hydrogen (HI) data from the Leiden/Argentina/Bonn (LAB) survey. However, the poor spatial resolution of the single dish data may have a significant effect on the derived column densities. To investigate this, we present new high-resolution HI observations with the Austr…
Polarization of interstellar dust emission is a powerful probe of dust properties and magnetic field structure. Yet studies of external galaxies are hampered by foreground dust contribution. The aim of this study is to separate the polarised signal from the Large Magellanic Cloud (LMC) from that of the Milky Way (MW) in order to construct a wide-field, spatially complete map of dust polarization using the Planck 353 GHz data. To estimate the foreground polarization direction, we used velocity gradients in HI spectral line data and assessed the performance of the output by comparing to starligh…
The Blanco DECam Bulge Survey (BDBS) has imaged more than 200 square degrees of the southern Galactic bulge, providing photometry in the ugrizy filters for $\sim 250$ million unique stars. The presence of a strong foreground disk population, along with complex reddening and extreme image crowding, has made it difficult to constrain the presence of young and intermediate age stars in the bulge population. We employed an accurate cross-match of BDBS with the latest data release (EDR3) from the Gaia mission, matching more than 140 million sources with BDBS photometry and Gaia EDR3 photometry and …
White dwarfs comprise 95% of all stellar remnants, and are thus an excellent tracer of old stellar populations in the Milky Way. Current and planned telescopes are not able to directly probe the white dwarf population in its entirety due to its inherently low luminosity. However, the Galactic population of double white dwarf binaries gives rise to a millihertz gravitational-wave foreground detectable by the Laser Interferometer Space Antenna (LISA). Here we show how characterizing this foreground's angular power spectrum will enable us to probe the Galactic structure in a novel way and measure…
The overwhelming foreground causes severe contamination on the detection of 21-cm signal during the Epoch of Reionization (EoR). Among various foreground components, the Galactic free-free emission is less studied, so that its impact on the EoR observation remains unclear. To better constrain this emission, we perform the Monte Carlo simulation of H$α$ emission, which comprises direct and scattered H$α$ radiation from HII regions and warm ionized medium (WIM). The positions and radii of HII regions are quoted from the WISE HII catalog, and the WIM is described by an axisymmetric model. The sca…
Optical stellar polarimetry in the Perseus molecular cloud direction is known to show a fully mixed bi-modal distribution of position angles across the cloud (Goodman et al. 1990). We study the Gaia trigonometric distances to each of these stars and reveal that the two components in position angles trace two different dust clouds along the line of sight. One component, which shows a polarization angle of -37.6 deg +/- 35.2 deg and a higher polarization fraction of 2.0 +/- 1.7%, primarily traces the Perseus molecular cloud at a distance of 300 pc. The other component, which shows a polarization…
Using high-resolution data from the Galactic Arecibo L-Band Feed Array HI (GALFA-HI) survey, we show that linear structure in Galactic neutral hydrogen (HI) correlates with the magnetic field orientation implied by Planck 353 GHz polarized dust emission. The structure of the neutral interstellar medium is more tightly coupled to the magnetic field than previously known. At high Galactic latitudes, where the Planck data are noise-dominated, the HI data provide an independent constraint on the Galactic magnetic field orientation, and hence the local dust polarization angle. We detect strong cros…
The observations of fluctuations in the cosmic microwave background provide information about primordial inhomogeneities in the universe. However, the B-mode polarization of the inflationary gravitational wave is contaminated by the Galactic foreground polarized radiation arising from dust aligned by interstellar magnetic fields. To trace magnetic fields we use the Velocity Gradient Technique, which employs a modern understanding of the nature of magneto-hydrodynamics turbulent motions. In this paper, we combine the VGT with the Principal Component Analysis (PCA) to improve the accuracy of mag…
Polarized Galactic foregrounds are one of the primary sources of systematic error in measurements of the B-mode polarization of the Cosmic Microwave Background (CMB). Experiments are becoming increasingly sensitive to complexities in the foreground frequency spectra that are not captured by standard parametric models, potentially affecting our ability to efficiently separate out these components. Employing a suite of dust models encompassing a variety of physical effects, we simulate observations of a future seven-band CMB experiment to assess the impact of these complexities on parametric com…
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.
The overwhelming foreground contamination hinders the accurate detection of the 21-cm signal of neutral hydrogen during the Epoch of Reionization (EoR). Among various foreground components, the Galactic free-free emission is less studied, so that its impact on the EoR observations remains unclear. In this work, we employ the observed $\rm Hα$ intensity map with the correction of dust absorption and scattering, the Simfast21 software, and the latest SKA1-Low layout configuration to simulate the SKA "observed" images of Galactic free-free emission and the EoR signal. By calculating the one-dimen…
Resolving the phase structure of neutral hydrogen (HI) is crucial for understanding the life cycle of the interstellar medium (ISM). However, accurate measurements of HI temperature and density are limited by the availability of background continuum sources for measuring HI absorption. Here we test the use of deep learning for extracting HI properties over large areas without optical depth information. We train a 1D convolutional neural network using synthetic observations of 3D numerical simulations of the ISM to predict the fraction of cold neutral medium (f_CNM) and the correction to the op…
$Ab$ $initio$ 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）
The large-scale magnetic field of the Milky Way is thought to be created by an alpha-Omega dynamo, which implies that it should have opposite handedness North and South of the Galactic midplane. Here we attempt to detect a variation in handedness using polarization data from the Wilkinson Microwave Anisotropy Probe. Previous analyzes of the parity-even and parity-odd parts of linear polarization of the global dust and synchrotron emission have focused on quadratic correlations in spectral space of, and between, these two components. Here, by contrast, we analyze the parity-odd polarization its…
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…
[Abridged] We present updated estimates of Galactic foreground emission using seven years of WMAP data. Using the power spectrum of differences between multi-frequency template-cleaned maps, we find no evidence for foreground contamination outside of the updated (KQ85y7) foreground mask. We place a 15 microKelvin upper bound on rms foreground contamination in the cleaned maps used for cosmological analysis. We find no indication in the polarization data of an extra "haze" of hard synchrotron emission from energetic electrons near the Galactic center. We provide an updated map of the cosmic mic…
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, …
This paper provides full sky maps of foreground emission in all WMAP channels, with very low residual contamination from the Cosmic Microwave Background (CMB) anisotropies and controlled level of instrumental noise. Foreground maps are obtained by subtraction of a properly filtered CMB map, obtained from linear combinations of needlet-based representations of all WMAP observations and of a 100-micron map. The error in the reconstructed foreground maps on large scales is significantly lower than the original error due to CMB contamination, while remaining of the order of the original WMAP noise…
Recent Planck observations have revealed some of the important statistical properties of synchrotron and dust polarisation, namely, the $B$ to $E$ mode power and temperature-$E$ (TE) mode cross-correlation. In this paper, we extend our analysis in Kandel et al. (2017) that studied $B$ to $E$ mode power ratio for polarised dust emission to include TE cross-correlation and develop an analogous formalism for synchrotron signal, all using a realistic model of magnetohydrodynamical (MHD) turbulence. Our results suggest that the Planck results for both synchrotron and dust polarisation can be unders…
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…
The characterization of the dust polarization foreground to the Cosmic Microwave Background (CMB) is a necessary step towards the detection of the B-mode signal associated with primordial gravitational waves. We present a method to simulate maps of polarized dust emission on the sphere, similarly to what is done for the CMB anisotropies. This method builds on the understanding of Galactic polarization stemming from the analysis of Planck data. It relates the dust polarization sky to the structure of the Galactic magnetic field and its coupling with interstellar matter and turbulence. The Galac…
Characterizing the sub-mm Galactic emission has become increasingly critical especially in identifying and removing its polarized contribution from the one emitted by the Cosmic Microwave Background (CMB). In this work, we present a parametric foreground removal performed onto sub-patches identified in the celestial sphere by means of spectral clustering. Our approach takes into account efficiently both the geometrical affinity and the similarity induced by the measurements and the accompanying errors. The optimal partition is then used to parametrically separate the Galactic emission encoding…
Understanding the non-Gaussian nature of Galactic foreground emissions towards small scales
Texas A&M University（德州农工大学）；Indian Institute of Astrophysics（印度天体物理研究所）；Korea Institute for Advanced Study (KIAS)（韩国高等研究院）；National Institute of Science Education and Research（国家科学教育研究所）；Homi Bhabha National Institute（霍米·巴巴国立研究所）；University of Alberta（阿尔伯塔大学）；Raman Research Institute（拉曼研究所）；Inter University Centre for Astronomy and Astrophysics（大学间天文与天体物理中心）
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）
We analyse WMAP 7-year temperature data, jointly modeling the cosmic microwave background (CMB) and Galactic foreground emission. We use the Commander code based on Gibbs sampling. Thus, from the WMAP7 data, we derive simultaneously the CMB and Galactic components on scales larger than 1deg with sensitivity improved relative to previous work. We conduct a detailed study of the low-frequency foreground with particular focus on the "microwave haze" emission around the Galactic center. We demonstrate improved performance in quantifying the diffuse galactic emission when Haslam 408MHz data are inc…
Templates for polarised emission from Galactic foregrounds at frequencies relevant to Cosmic Microwave Background (CMB) polarisation experiments are obtained by modelling the Galactic Magnetic Field (GMF) on large scales. This work extends the results of O'Dea et al. by including polarised synchrotron radiation as a source of foreground emission. The polarisation direction and fraction in this calculation are based solely on the underlying choice of GMF model and therefore provide an independent prediction for the polarisation signal on large scales. Templates of polarised foregrounds may be o…
Total-power radiometry with individual meter-wave antennas is a potentially effective way to study the Cosmic Dawn ($z\sim20$) through measurement of sky brightness arising from the $21$~cm transition of neutral hydrogen, provided this can be disentangled from much stronger Galactic and extra-galactic foregrounds. In the process, measured spectra of integrated sky brightness temperature can be used to quantify the foreground emission properties. In this work, we analyze a subset of data from the Large-aperture Experiment to Detect the Dark Age (LEDA) in the range $50-87$~MHz and constrain the …
We present results from a sample of XMM-Newton and Suzaku observations of interstellar clouds that cast shadows in the soft X-ray background (SXRB) - the first uniform analysis of such a sample from these missions. By fitting to the on- and off-shadow spectra, we separated the foreground and Galactic halo components of the SXRB. We tested different foreground models - two solar wind charge exchange (SWCX) models and a Local Bubble (LB) model. We also examined different abundance tables. We found that Anders & Grevesse (1989) abundances, commonly used in previous SXRB studies, may result in ove…
The cosmic microwave background (CMB) is one of the finest probes of cosmology. Its all-sky temperature and linear polarization (LP) fluctuations have been measured precisely at a level of deltaT/TCMB ~10^{-6}. In comparison, circular polarization (CP) of the CMB, however, has not been precisely explored. Current upper limit on the CP of the CMB is at a level of deltaV/TCMB ~10^{-4} and is limited on large scales. Some of the cosmologically important sources which can induce a CP in the CMB include early universe symmetry breaking, primordial magnetic field, galaxy clusters and Pop III stars (…
We investigate possible imprints of galactic foreground structures such as the "radio loops" in the derived maps of the cosmic microwave background. Surprisingly there is evidence for these not only at radio frequencies through their synchrotron radiation, but also at microwave frequencies where emission by dust dominates. This suggests the mechanism is magnetic dipole radiation from dust grains enriched by metallic iron or ferrimagnetic materials. This new foreground we have identified is present at high galactic latitudes, and potentially dominates over the expected $B$-mode polarization sig…
The Internal Linear Combination (ILC) method has been extensively used to extract the cosmic microwave background (CMB) anisotropy map from foreground contaminated multi-frequency maps. However, the performance of simple ILC is limited and can be significantly improved by heavily constraint equations, dubbed cILC. The standard ILC and cILC works on the spin-0 field. Recently, a generalized version of ILC is developed to estimate polarization maps in which the quantity $Q \pm iU$ is combined at multiple frequencies using complex coefficients called Polarization ILC (PILC). A statistical moment …
We compute the cross correlation of the intensity and polarisation from the 5-year WMAP data in different sky-regions with respect to template maps for synchrotron, dust, and free-free emission. We derive the frequency dependence and polarisation fraction for all three components in 48 different sky regions of HEALPix (Nside=2) pixelisation. The anomalous emission associated with dust is clearly detected in intensity over the entire sky at the K (23 GHz) and Ka (33 GHz) WMAP bands, and is found to be the dominant foreground at low Galactic latitude, between b=-40 and b=+10. The synchrotron spe…
We present observations and CMB foreground analysis of the Parkes Galactic Meridian Survey (PGMS), an investigation of the Galactic latitude behaviour of the polarized synchrotron emission at 2.3 GHz with the Parkes Radio Telescope. The survey consists of a 5-deg wide strip along the Galactic meridian l=254-deg extending from Galactic plane to South Galactic pole. We identify three zones distinguished by polarized emission properties: the disc, the halo, and a transition region connecting them. The halo section lies at latitudes |b| > 40-deg and has weak and smooth polarized emission mostly at…
Extending Galactic foreground emission with neural networks
Università degli Studi di Catania（卡塔尼亚大学）；INFN - Sezione di Catania（意大利国家核物理研究所卡塔尼亚分部）；INAF - Osservatorio Astrofisico di Catania（意大利国家天体物理研究所卡塔尼亚天文台）；Università di Roma Tor Vergata（罗马二大）；INFN Sezione di Roma2, Università di Roma Tor Vergata（意大利国家核物理研究所罗马二大分部）
