Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.02301

Optimizing spectral-matching component separation for measuring CMB B-mode polarization with a satellite mission

Hoang Viet Tran·Guillaume Patanchon·Michele Citran·Benjamin Beringue
View original source ↗Read source document ↗Export metadata ↓

Abstract

The measurement of primordial CMB B-mode polarization is fundamentally limited by our ability to separate this faint signal from bright and complex Galactic foregrounds. Spectral Matching Independent Component Analysis (SMICA) offers a flexible, semi-blind approach to this foreground-cleaning problem. However, its standard implementation relies on a physically unrealistic assumption of non-spatially varying foreground emission, reducing the efficiency of the method. In this work, we develop two complementary strategies to address this limitation at the component-separation level. First, we augment SMICA with effective foreground components beyond the physical dust and synchrotron degrees of freedom. Second, we extend SMICA to operate independently on subsets of the sky, better capturing local variations in the foreground emission. Beyond component separation, we further explore a likelihood-level marginalization procedure using internally reconstructed foreground templates. We demonstrate the performance of the pipeline on simulated LiteBIRD-like observations, using foreground models of increasing complexity based on $\texttt{d1s1}$ and $\texttt{d10s5}$. Combining our component-separation improvements with template marginalization brings the recovered tensor-to-scalar ratio $r$ to effectively unbiased levels, with statistical uncertainties on the order of $10^{-3}$ or below.

Explore related subjects

astro-ph.IMastro-ph.CO

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Hoang Viet Tran, Guillaume Patanchon, Michele Citran, Benjamin Beringue. 2026-10-01. Optimizing spectral-matching component separation for measuring CMB B-mode polarization with a satellite mission. https://arxiv.org/abs/2610.02301

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

A chemically etched D-band waveguide orthomode transducer for CMB measurements

This study presents a prototype D-band waveguide orthomode transducer (OMT) fabricated using chemically etched brass platelets. This method offers a fast, cost-effective, and scalable approach for producing waveguide OMTs above 100 GHz, making it well-suited for current and future Cosmic Microwave Background polarization experiments, where large focal planes with thousands of receivers are required to detect the faint primordial \textit{B}-modes. Chemical etching has already demonstrated its effectiveness in manufacturing corrugated feedhorn arrays with state-of-the-art performance up to 150 GHz. Here, we evaluate its applicability to more complex structures, such as OMTs. We designed a single OMT prototype operating in the 130-170 GHz range, fabricated by chemically etching 0.15 mm-thick brass plates, which were then stacked, aligned, and mechanically clamped. Simulations based on metrological measurements of the OMT profile predict return losses below $-$10 dB, isolation better than $-$30 dB, and transmission around $-$0.5 dB. The measured transmission and isolation, however, is around $-$1.5/$-$2 dB and $<-$20 dB, respectively. Further simulations show that the degradation in the transmission is related to defects and roughness along the etched profile ($\mathrm{RMS}\simeq$3 $μ$m), which is a typical and unavoidable effect of chemical etching. The discrepancy in isolation, instead, could arise from a slight rotation ($\sim$3$^{\circ}$) of the polarization angle within the measurement chain. Our results show that chemical etching is a fast, low-cost, and scalable technique for producing waveguide OMTs with state-of-the-art performance in terms of return loss and isolation. However, at frequencies above 100 GHz the transmission coefficient may degrade due to the mechanical precision limitations of chemical etching.

astro-ph.IM↗
arXiv2026

On the Nonlinear Dependence of Underground Muon Rate on Atmospheric Temperature Observed at Daya Bay

The underground cosmic-ray muon rate is modulated by atmospheric temperature. It can be explained by the theories of Barrett, Gaisser, and others. However, the Daya Bay Neutrino Experiment observes a nonlinear temperature dependence. We find that, when deriving the temperature dependence of the muon rate, existing theories consider only the impact of the local temperature on muon production at the layer where muons are produced. In this work, we provide a more general solution to the cascade equations that fully depicts how the entire temperature profile influences the final muon rate. The corresponding definitions of the effective temperature weight and temperature coefficient are also presented. We have examined the results using the numerical tool MCEq with real atmospheric temperature inputs. A linear modulation is recovered and verified. This work can help explain the nonlinear effect observed at Daya Bay and provide a more refined theoretical framework for calculating the temperature coefficient in other experiments.

astro-ph.IM↗
arXiv2026

A space of inference spaces in the space sciences - parametric Bayesian inference in astronomy, cosmology and particle physics

A sample of parametric Bayesian inference applications from astronomy, cosmology and particle physics is studied, augmented by mock data sets and toy problems. The parameter spaces of these parametric physical models and their posterior distributions from analysing specific data are characterized by (1) the number of model parameters, (2) whether the posterior shape is similar to a Gaussian, (3) whether the posterior has light or heavy tails, (4) how small the posterior is compared to the prior, i.e., how informative the data are, (5) whether some parameters remain unconstrained while others are highly constrained, (6) whether the posterior has multiple, disconnected modes, and (7) whether the inference undergoes phase transitions. These axis define a parameter space of inference problems. We characterize each of the inference problems and observe that inference in astrophysics spans the entire parameter space, from low to high dimensionality, mono- to multi-modal, and a variety of complex distributions that range from uninformative to highly informative. Furthermore, the computational cost of the physical models can range from milliseconds to dozens of seconds. The collated sample of inference problems is proposed as a standard test bed for new samplers. For reproducibility and ease of use, a Docker compute image is provided.

astro-ph.IM↗