A three-dimensional reconstruction of the interstellar magnetic field toward a star-forming region

Abstract

Context. The polarized thermal emission from interstellar dust offers a valuable tool for probing both the dust and the magnetic field in the interstellar medium (ISM). However, existing observations only yield the total amount of dust emission along the line of sight (LoS), with no information on its LoS distribution. Aims. We present a new method designed to give access to the LoS distribution of the dust emission, both in terms of intensity and polarization. Methods. We relied on three kinematic gas tracers (HI, 12CO, and 13CO emission lines) to identify the different clouds present along the LoS. We decomposed the measured intensity of the dust emission, $I_d$, into separate contributions from these clouds. We performed a similar decomposition of the measured Stokes parameters for linear polarization, $Q_d$ and $U_d$, to derive the polarization parameters of the different clouds, and from this we inferred the clouds' magnetic field orientations. Results. We applied our method to a $3{\mathrm{deg}}^2$ region of the sky, centered on $(l,b)=(139°30^{\prime },-3°16^{\prime })$ and exhibiting signs of star formation activity. We found this region to be dominated by an extended and bright cloud with nearly horizontal magnetic field, as expected from the nearly vertical polarization angles measured by Planck. More importantly, we detected the presence of two smaller, depolarizing molecular clouds with very different magnetic field orientations in the plane of the sky ($\simeq 65°$ and $\simeq 45°$ from the horizontal). This is a novel and viable result, which cannot be directly read off the Planck polarization maps. Conclusions. The application of our method to the G139 region convincingly demonstrates the need to complement 2D polarization maps with 3D kinematic information when looking for reliable estimates of magnetic field orientations.

26 pages, 10 figures, 3 tables, 3 appendices

References in corpus (27)

• HI4PI: A full-sky HI survey based on EBHIS and GASS
• Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust
• Gaia-2MASS 3D maps of Galactic interstellar dust within 3 kpc
• The Milky Way Imaging Scroll Painting (MWISP): Project Details and Initial Results from the Galactic Longitude of 25.8deg to 49.7deg
• Updated Gaia-2MASS 3D maps of Galactic interstellar dust
• Radiative torque alignment: Essential Physical Processes
• Planck intermediate results. XX. Comparison of polarized thermal emission from Galactic dust with simulations of MHD turbulence
• Pulsar Rotation Measures and Large-scale Magnetic Field Reversals in the Galactic Disk
• Low-frequency Faraday rotation measures towards pulsars using LOFAR: probing the 3-D Galactic halo magnetic field
• On the radiation driven alignment of dust grains: Detection of the polarization hole in a starless core
• On the Three-Dimensional Structure of Local Molecular Clouds
• Faraday tomography of the local interstellar medium with LOFAR: Galactic foregrounds towards IC342
• Submillimeter and Far-Infrared Polarimetric Observations of Magnetic Fields in Star-Forming Regions
• ROHSA: Regularized Optimization for Hyper-Spectral Analysis - Application to phase separation of 21 cm data
• Planck intermediate results. L. Evidence for spatial variation of the polarized thermal dust spectral energy distribution and implications for CMB $B$-mode analysis
• Plasma turbulence in the interstellar medium
• Evidence for Line-of-Sight Frequency Decorrelation of Polarized Dust Emission in $Planck$ Data
• A Morphological Classification of 18190 Molecular Clouds Identified in ${}^{12}$CO Data from the MWISP Survey
• FEDReD II : 3D Extinction Map with 2MASS and Gaia DR2 data
• Starlight-polarization-based tomography of the magnetized interstellar medium: PASIPHAE's line-of-sight inversion method
• The first degree-scale starlight-polarization-based tomography map of the magnetized interstellar medium
• Faraday tomography of LoTSS-DR2 data: I. Faraday moments in the high-latitude outer Galaxy and revealing Loop III in polarisation
• Two-component Magnetic Field along the Line of Sight to the Perseus Molecular Cloud: Contribution of the Foreground Taurus Molecular Cloud
• Mapping the Galactic Magnetic Field Orientation and Strength in Three Dimensions
• Will ALMA Reveal the True Core Mass Function of Protoclusters?
• Molecular Gas Structures traced by ${}^{13}$CO Emission in the 18,190 ${}^{12}$CO Molecular Clouds from the MWISP Survey
• Faraday tomography of LoTSS-DR2 data: II. Multi-tracer analysis in the high-latitude outer Galaxy