Colloque national CMB-France #3

20 juin 2022, 09:30 → 21 juin 2022, 17:00 Europe/Paris

L'initiative CMB-France vise à mettre en place une animation scientifique au niveau national autour des études CMB (cmb-france.cnrs.fr).

Le CMB-France #3 aura lieu les 20 et 21 Juin 2022 à l'IAP.

 

L'inscription est gratuite mais obligatoire: ici.

 

CMB-France peut prendre en charge les missions (dans la limite des stocks disponibles). Renseignez-vous auprès de M. Tristram.

 

L’agenda est en cours de finalisation mais l’idée de ces colloques est de:

• présenter les nouveautés scientifiques et les nouveaux résultats dans le domaine
• donner un statut sur l’avancement des expériences ou des projets en cours
• permettre aux jeunes (post-doc, PhD) de présenter leur travail

N’hésitez pas à nous contacter ou à soumettre vos propositions de presentation (avant le 10 Juin).

 

Les informations de connexion seront envoyées par la mailing-liste cmb-france. Pensez à vous inscrire.

 

  Cette action est soutenue par le PNCG.

lundi 20 juin

14:00 → 14:30 Introduction

14:30 → 17:00 Session #1

14:30 Searching for physics beyond the standard model with Planck, SPT, and ACT data.

Measurements of the CMB temperature and polarisation power spectra provide high-precision constraints on cosmological parameters and point to a value for the expansion rate today 5 sigma lower than what supernovae and distance-ladder analyses find.
While the latter analyses measure the Hubble constant directly, we must assume a given cosmological model to infer the expansion rate from CMB data.
Hence, changes to physics at early times away from standard model dynamics result in different parameter constraints from CMB data - and provide a possible pathway to resolving the Hubble tension.
In this talk, I explore constraints on two such models, primordial magnetic fields and early dark energy using the latest Planck, South Pole Telescope (SPT), and Atacama Cosmology Telescope data.
I present new limits on primordial magnetic fields and show how a 3.3$\sigma$ hint for early dark energy emerges in the CMB data.
From these results I motivate the joint analysis of CMB temperature and polarisation power spectra.
I present the status of this ongoing analysis for SPT data and highlight the internal consistency of the data set.

Orateur: Lennart Balkenhol (University of Melbourne)

France_CMB_2022_talk_redac.pdf

15:10 Building SPT3G 2019/2020 likelihood

The South Pole Telescope (SPT) is observing the CMB anisotropies with arcminute resolution using its state-of-the-art camera (SPT-3G). Constraints on cosmological parameters from the obtained data will be as tight as Planck’s one, while remaining independent from the satellite experiment, thus allowing to test the consistency of the two dataset and investigate new physics. A reliable estimation of cosmological parameters requires accurate covariance matrices. In this talk, I will present my recent work on analytical pseudo-power spectrum covariance matrices for small survey area. First, I will introduce an efficient (but computationally expensive) exact calculation of such matrices. Then, using it as a reference, I estimate the accuracy of existing and new approximations of the covariance matrix. Finally, I will present solutions to mitigate the effect of point source masking.

Orateur: Etienne Camphuis (Institut d'Astrophysique de Paris)

20220620_cmbfrance.pdf

15:50 Café

16:20 Simultaneous determination of miscalibrated polarization angles and cosmic birefringence from Planck PR4

We present a new implementation of the methodology proposed in Minami et al. (2019) for the simultaneous determination of cosmic birefringence and the miscalibration of polarization angles based on a fast and analytical maximum likelihood solution iterative algorithm. Following the hint of the 2.4σ cosmic birefringence signal of β = 0.35◦ ± 0.14◦ found by Minami & Komatsu (2020) in Planck 2018 polarization data (PR3), we apply this methodology to continue the search for the signature of parity-violating physics in the Cosmic Microwave Background using data from Planck PR4 (NPIPE reprocessing). For nearly full-sky data, we initially confirm the previously re- ported value with a smaller statistical uncertainty. We also find that the values of β decrease as the Galactic mask is enlarged, which can be interpreted as the effect of polarized foreground emis- sion. Acknowledging that the miscalibration of polarization angles is not the only instrumental systematic that can create spurious TB and EB correlations, a detailed study of NPIPE’s end-to- end simulations is conducted to evaluate the possible impact of systematics like cross-polarization effects or temperature-to-polarization leakage. This study demonstrates that the β measurements are not significantly affected by any of the known systematics, reinforcing the hypothesis that the decline on β as the Galactic mask is enlarged is driven by the foreground EB correlation. Finally, two independent ways to model the foreground EB contribution and mitigate its impact on β are proposed. Although the good agreement between the two models is encouraging, we do not as- sign cosmological significance to the measured value of β until we improve our knowledge of the foreground polarization.

Orateur: Patricia DIEGO-PALAZUELOS

Birefringence_CMBFrance.pdf

17:00 → 17:45 Session #2: Discussion

17:00 CMB-S4

Status of CMB-S4

Orateur: Julian Borrill

An Introduction To CMB-S4.pdf

mardi 21 juin

09:30 → 12:40 Session #3: CMB Foregrounds

09:30 New model of Planck polarized dust maps using Cross Wavelet Scattering Transform

The fine measurement of the polarized emission of the CMB is intimately linked to the ability to separate it from the Galactic foregrounds. A specific difficulty for this goal is to take into account the spatial non-Gaussian structure of these foregrounds. In this work, we propose a new method that is able to extract the non-Gaussian features of the galactic dust emission from noisy observations, that we apply to a full-sky map from the SRoll2 HFI-Planck data at 353Ghz. This method introduces in particular the Cross Wavelet Scattering Transform (CWST). These statistics, which are able to characterize non-Gaussian statistical dependencies between different processes, play a crucial role in extracting the features of the dust emission from two half-missions with different noise realizations. This statistical separation of components allows to recover the statistics of the dust emission, including its non-Gaussian properties, until close to lmax~800, where the noise dominates in power by a factor 100 in power spectrum ( fsky=0.5), as well as to generate new realizations of the foregrounds with reproduce these statistical properties up to the same scale. Thanks to their realistic non-Gaussian features, we expect these new models of galactic dust emission to play a strategic role for future CMB analyses.

Orateur: Dr Erwan Allys (LPENS)

CMB_Fr_21 06.pdf

10:10 High precision modeling of polarized signals

The modeling and removal of foregrounds poses a major challenge to searches for signals from inflation using the cosmic microwave background (CMB). In particular, the modeling of CMB foregrounds including various spatial averaging effects introduces multiple complications that will have to be accounted for in upcoming analyses.
In this work, we introduce the generalization of the intensity moment expansion to the spin-2 field of linear polarization: the \emph{spin-moment} expansion.
Within this framework, moments become spin-2 objects that are directly related to the underlying spectral parameter and polarization angle distribution functions. In obtaining the required expressions for the polarization modeling, we highlight the similarities and differences with the intensity moment methods. A spinor rotation in the complex plane with frequency naturally arises from the first order moment when the signal contains both SED distortions and polarization mixing. Additional dependencies are introduced at higher order, and we demonstrate on several illustrative examples how these can be accounted for.
Our new modeling of the polarized SED reveals to be a powerful tool to model the frequency dependence of the polarization angle. As such, it can be immediately applied to numerous astrophysical situations.

Orateur: Léo Vacher (Institut de recherche en astrophysique et planétologie (IRAP))

spin-moments.pdf

10:50 Café

11:20 Statistical separation of dust and CIB with Wavelet Phase Harmonics (WPH)

Modelling the emission of Galactic dust is a main challenge for CMB polarization experiments. Current models make use of Planck total intensity data plagued by the difficulty of separating dust emission from the Cosmic Infrared Background (CIB). We address this outstanding difficulty from a new perspective compared to previous attempts. We will show that dust and CIB may be statistically separated using their radically different structure on the sky. Our approach makes uses of a CIB model map built from a cosmological simulation and Herschel/SPIRE observations. We use the Wavelet Phase Harmonics (WPH) statistics to separate dust and CIB and derive a statistical, non-Gaussian, model of each component. We demonstrate and validate the separation on mock data, before applying it to Herschel observations of cosmological fields and the diffuse interstellar medium (ISM) at high Galactic latitude. The two models derived from our analysis of Herschel observations are generative models, which may be used to simulate maps of each component, essentially free from mutual contamination. We will present an astrophysical application where we extend our statistical modelling to HI observations to investigate the dynamical coupling of gas and dust, down to the smallest spatial scales, a few hundredths of a parsec in the diffuse ISM, probed by Herschel.

Orateur: Constant Auclair (LPENS)

12:00 Polarized foregrounds

I will present new maps of polarised synchrotron and dust emission extracted from Planck and WMAP data.

Orateur: Jacques Delabrouille (IN2P3)

Delabrouille-synchrotron.pdf

14:00 → 16:45 Session #4

14:00 Dust polarization spectral dependence from Planck HFI data

The search for the primordial B-modes in the cosmic microwave background (CMB) polarization depends on the separation from the brighter dust foreground signal. In this context, the characterization of the spatial variations of the spectral energy distribution (SED) of thermal dust in polarization has become a critical subject of study.
This contribution aims at presenting a power spectra analysis of Planck data, which improves on previous studies by using the newly released SRoll2 maps that better correct systematic effects, and by extending the analysis to regions near the Galactic plane. Our analysis focuses on the lowest multipoles between l = 4 , and 32, and three sky areas with sky fractions of fsky = 80%, 90%, and 97%. The mean dust SED for polarization and the 353 GHz Q and U maps are used to compute residual maps at 100, 143 and 217 GHz, highlighting spatial variations of the dust polarization SED. Residuals are detected at the three frequencies for the three sky areas. The power spectra show that models based on total intensity data are underestimating by a significant factor the complexity of dust polarized CMB foreground. This analysis emphasizes the need to include variations of polarization angles in simulations of the dust polarized CMB foreground and the importance to consider the geometrical properties of the polarization. The frequency dependence of the EE and BB power spectra of residual maps yields further insight, suggesting that a significant refinement to dust modeling will be needed to ensure an unbiased detection of the CMB primordial B-modes at the precision required by future CMB experiments.

Orateur: Alessia Ritacco (INAF, LPENS)

AR_CMBFrance_v1.pdf

14:40 Detection and reconstruction of SZ effect with Deep Learning

The Planck collaboration has extensively used the six Planck HFI frequency maps to detect the Sunyaev-Zel’dovich effect (SZ) with dedicated methods, for example by applying (i) component separation to construct a full-sky map of the y parameter or (ii) matched multi-filters to detect galaxy clusters via their hot gas. Although powerful, these methods may still introduce biases in the detection of the sources or in the reconstruction of the SZ signal due to prior knowledge. The wide sky fraction and the large number of frequencies used in CMB observations make them a gold mine for applications of deep learning, especially to recover tiny signals such as SZ. I will present first results on such application to detect the SZ signal from the Planck HFI frequency maps. Trained on Planck clusters, we can recover them in a test area and in the full sky we detect more than 18 000 other potential SZ sources for which we have statistical indications of galaxy cluster signatures, by stacking at their positions at different wavelengths. We further perform a component separation on a simulated sky (WebSky) based on Convolutional Neural Network to try to break the known degeneracy between the infrared emission and the SZ effect. Deep learning applications shown in these proof-of-concept studies are promising for the detections of galaxy clusters and the characterisation of large-scale structures via their hot gas in future CMB experiments such as Simons Observatory.

Orateur: Dr Victor Bonjean (IAC)

15:20 Direct measurement of the hydrostatic bias

The NIKA2 Sunyaev Zel’dovich Large Program (LPSZ) aims at studying 45 clusters of galaxies at intermediate and high redshift (0.5 < z < 0.9). A joint analysis of the thermal SZ (tSZ) effect on CMB at millimetre wavelength with the NIKA2 camera and in X-ray with XMM-Newton satellite permits the reconstruction of clusters’ thermodynamical properties and hydrostatic masses. These mass estimates are fundamental for cluster cosmology with the next generation of CMB experiments. Here, we test the robustness of LPSZ hydrostatic mass estimates against systematic effects induced by the data processing or the modelling. We illustrate these systematic effects with a multi-probe analysis of the well known galaxy cluster CL J1226.9+3332, which is a massive and high redshift cluster that has already been observed at several wavelengths. In addition, using Cluster Lensing And Supernova survey with Hubble (CLASH) observations we obtain estimates of the lensing masses for a common sample with the LPSZ. From this we are able to compare the different mass estimates and test the impact of systematic effects on the hydrostatic to lensing cluster mass bias.

Orateur: Miren Muñoz Echeverría (LPSC)

cmb21062022_MuñozEcheverría.pdf

16:00 Café