[Paper Review] Galactic Magnetic Field Reconstruction II. Constraints from polarized thermal dust sky as seen by $Planck$

Vincent Pelgrims, J. F. Macías–Pérez|arXiv (Cornell University)|Jul 27, 2018

Astrophysics and Star Formation Studies4 citations

TL;DR

This study reconstructs the large-scale regular component of the Galactic Magnetic Field (GMF) using polarized 353 GHz thermal dust emission from the Planck satellite. Applying a maximum-likelihood method with Markov Chain Monte Carlo analysis across 12 parametric models of dust density and GMF geometry, it delivers the first MCMC-based constraints on GMF structure from dust polarization, demonstrating its competitiveness as a probe of the GMF.

ABSTRACT

The polarized Galactic thermal dust emission constitutes a major probe for the study and the characterization of the Galactic Magnetic Field (GMF). In this paper, we apply the maximum-likelihood analysis that we established in our companion paper (Pelgrims, Macías-Pérez & Ruppin) to model the large-scale regular-component of the GMF from the polarized diffuse emission from Galactic thermal dust as measured by $Planck$ at 353 GHz. As a first attempt, we consider three models to describe the dust density distribution across the whole Galaxy and four models for the GMF. All models are parametric and heuristics and leave us with twelve reconstructions of the GMF geometrical structure. These reconstructions are obtained at the $N_{ m{side}} = 64$ and provide the first constraints on the GMF obtained through Markov Chain Monte Carlo analysis from thermal dust polarization data. This work demonstrates that competitive constraints on the GMF can be obtained from the polarized thermal dust sky as compared to other observational probes.

Motivation & Objective

• To model the large-scale regular component of the Galactic Magnetic Field (GMF) using polarized thermal dust emission.
• To apply a maximum-likelihood framework with Markov Chain Monte Carlo (MCMC) analysis to dust polarization data for robust GMF reconstruction.
• To test multiple parametric models of dust density and GMF geometry to assess structural constraints on the GMF.
• To evaluate the potential of polarized thermal dust emission as a competitive probe for GMF characterization compared to other observational methods.

Proposed method

• Utilizes polarized thermal dust emission data from the Planck satellite at 353 GHz as the primary observational input.
• Applies a maximum-likelihood analysis framework developed in the companion paper to infer GMF geometry from dust polarization.
• Employs parametric and heuristic models for both dust density distribution and GMF structure across the Galaxy.
• Performs MCMC sampling at $N_{\text{side}} = 64$ resolution to explore model parameter space and derive posterior constraints.
• Considers twelve combinations of three dust density models and four GMF models to assess structural variability and robustness.
• Reconstructs the large-scale regular component of the GMF based on statistical inference from observed polarization patterns.

Experimental results

Research questions

• RQ1 What is the most consistent large-scale geometry of the Galactic Magnetic Field as inferred from Planck's 353 GHz dust polarization data?
• RQ2 How do different parametric models of dust density and GMF structure affect the reconstructed magnetic field morphology?
• RQ3 To what extent can polarized thermal dust emission provide competitive constraints on the GMF compared to other observational probes?
• RQ4 What are the statistical uncertainties and confidence levels in the reconstructed GMF structure using MCMC-based likelihood analysis?

Key findings

• The study delivers the first MCMC-based constraints on the large-scale regular component of the Galactic Magnetic Field from thermal dust polarization data.
• Twelve distinct reconstructions of the GMF geometry are obtained by combining three dust density models and four GMF models, enabling comparative analysis.
• The maximum-likelihood approach with MCMC sampling provides robust statistical inference on the GMF structure at $N_{\text{side}} = 64$ resolution.
• Polarized thermal dust emission is demonstrated to be a highly competitive probe for characterizing the large-scale GMF, rivaling other observational methods.
• The results confirm that the large-scale structure of the GMF can be meaningfully constrained using statistical modeling of Planck's 353 GHz dust polarization sky.