Dust polarization modelling at large scale over the northern Galactic cap using EBHIS and <i>Planck</i> data

Adak, Debabrata; Ghosh, T.; Boulanger, F.; Haud, U.; Kalberla, P. M. W.; Martín, P. G.; Bracco, A.; Souradeep, T.

doi:10.1051/0004-6361/201936124

Cited by 15 publications

(15 citation statements)

References 66 publications

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“…Thus, while IVCs are likely not a concern for foreground modeling in this region, the LVC substructure may be cause to consider models with multiple dust components. The very nature of the multiphase neutral medium may cause such velocity substructure, as well as variations in dust properties (e.g., Murray et al 2020), motivating the incorporation of phase structure into foreground modeling (Ghosh et al 2017;Adak et al 2020).…”

Section: The Bicep/keck Fieldmentioning

confidence: 99%

“…In their approach, the number of layers was simply a free parameter of the model, unrelated to a specific physical quantity. In contrast, the model of Ghosh et al (2017) and Adak et al (2020) employs three discrete layers of dust, each associated with a different phase of the ISM. Their analysis is based on HI4PI data in the Galactic polar caps and also succeeds in reproducing observables in the polarized dust emission.…”

Section: Comparison Of the Number Of Clouds Per Sight Line With Previmentioning

confidence: 99%

“…Innovative, data-driven approaches are being developed to characterize the ISM properties (Clark et al 2015;Clark 2018;Philcox et al 2018;González-Casanova & Lazarian 2019;Zhang et al 2019). Recent studies try to construct realistic realizations of dust foregrounds using 3D dust maps (Martínez-Solaeche et al 2018) or H I data (Ghosh et al 2017;Clark & Hensley 2019;Lu et al 2020;Adak et al 2020;Hu et al 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Other studies adopt a more physically motivated assumption about the number of clouds per pixel. For example, Ghosh et al (2017) and Adak et al (2020) assume three dust layers, each arising from a different gas phase of the ISM. The approach of Martínez-Solaeche et al (2018) assumes that each distance bin in the 3D dust map of Green et al (2019) is a different dust layer.…”

Section: Introductionmentioning

confidence: 99%

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Maps of the Number of H i Clouds along the Line of Sight at High Galactic Latitude

Panopoulou

Lenz

2020

ApJ

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Characterizing the structure of the Galactic interstellar medium (ISM) in three dimensions is of high importance for accurate modeling of dust emission as a foreground to the cosmic microwave background (CMB). At high Galactic latitude, where the total dust content is low, accurate maps of the 3D structure of the ISM are lacking. We develop a method to quantify the complexity of the distribution of dust along the line of sight with the use of H I line emission. The method relies on a Gaussian decomposition of the H I spectra to disentangle the emission from overlapping components in velocity. We use this information to create maps of the number of clouds along the line of sight. We apply the method to (a) the high Galactic latitude sky and (b) the region targeted by the BICEP/Keck experiment. In the north Galactic cap we find on average three clouds per 0.2 square degree pixel, while in the south the number falls to 2.5. The statistics of the number of clouds are affected by intermediate-velocity clouds (IVCs), primarily in the north. IVCs produce detectable features in the dust emission measured by Planck. We investigate the complexity of H I spectra in the BICEP/Keck region and find evidence for the existence of multiple components along the line of sight. The data (doi: 10.7910/DVN/8DA5LH) and software are made publicly available and can be used to inform CMB foreground modeling and 3D dust mapping.Unified Astronomy Thesaurus concepts: Interstellar medium (847); Neutral hydrogen clouds (1099); Interstellar atomic gas (833)

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Section: The Bicep/keck Fieldmentioning

confidence: 99%

Section: Comparison Of the Number Of Clouds Per Sight Line With Previmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Maps of the Number of H i Clouds along the Line of Sight at High Galactic Latitude

Panopoulou

Lenz

2020

ApJ

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“…This approach differs from previous work where dust polarization maps are computed from a phenomenological model and ancillary observations (Planck Collaboration Int. XLII 2016; Ghosh et al 2017;Vansyngel et al 2017;Levrier et al 2018;Adak et al 2020;Clark & Hensley 2019) or directly from numerical simulations (Kim et al 2019). It follows what has been done for dust total intensity by Allys et al (2019) using the RWST, and Aylor et al (2019) using a Generative Adversarial Network.…”

Section: Random Syntheses Ofq + Iũ Polarization Mapsmentioning

confidence: 79%

Statistical description of dust polarized emission from the diffuse interstellar medium

Blancard

Levrier

Allys

et al. 2020

A&A

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The statistical characterization of the diffuse magnetized interstellar medium (ISM) and Galactic foregrounds to the cosmic microwave background (CMB) poses a major challenge. To account for their non-Gaussian statistics, we need a data analysis approach capable of efficiently quantifying statistical couplings across scales. This information is encoded in the data, but most of it is lost when using conventional tools, such as one-point statistics and power spectra. The wavelet scattering transform (WST), a low-variance statistical descriptor of non-Gaussian processes introduced in data science, opens a path towards this goal. To establish the methodology, we applied the WST to noise-free maps of dust polarized thermal emission computed from a numerical simulation of magnetohydrodynamical turbulence in the diffuse ISM. We analyzed normalized complex Stokes maps and maps of the polarization fraction and polarization angle. The WST yields a few thousand coefficients; some of them measure the amplitude of the signal at a given scale, and the others characterize the couplings between scales and orientations. The dependence on orientation can be fitted with the reduced wavelet scattering transform (RWST), an angular model introduced in previous works for total intensity maps. The RWST provides a statistical description of the polarization maps, quantifying their multiscale properties in terms of isotropic and anisotropic contributions. It allowed us to exhibit the dependence of the map structure on the orientation of the mean magnetic field and to quantify the non-Gaussianity of the data. We also used RWST coefficients, complemented by additional constraints, to generate random synthetic maps with similar statistics. Their agreement with the original maps demonstrates the comprehensiveness of the statistical description provided by the RWST. This work is a step forward in the analysis of observational data and the modeling of CMB foregrounds. We also release PyWST, a public Python package to perform WST and RWST analyses of two-dimensional data.

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Compressed magnetized shells of atomic gas and the formation of the Corona Australis molecular cloud

Bracco

Bresnahan

Palmeirim

et al. 2020

A&A

Self Cite

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We present the identification of the previously unnoticed physical association between the Corona Australis molecular cloud (CrA), traced by interstellar dust emission, and two shell-like structures observed with line emission of atomic hydrogen (HI) at 21 cm. Although the existence of the two shells had already been reported in the literature, the physical link between the HI emission and CrA had never been highlighted until now. We used both Planck and Herschel data to trace dust emission and the Galactic All Sky HI Survey (GASS) to trace HI. The physical association between CrA and the shells is assessed based both on spectroscopic observations of molecular and atomic gas and on dust extinction data with Gaia. The shells are located at a distance between ~140 and ~190 pc, which is comparable to the distance of CrA, which we derived as (150.5 ± 6.3) pc. We also employed dust polarization observations from Planck to trace the magnetic-field structure of the shells. Both of them show patterns of magnetic-field lines following the edge of the shells consistently with the magnetic-field morphology of CrA. We estimated the magnetic-field strength at the intersection of the two shells via the Davis-Chandrasekhar-Fermi (DCF) method. Despite the many caveats that are behind the DCF method, we find a magnetic-field strength of (27 ± 8) μG, which is at least a factor of two larger than the magnetic-field strength computed off of the HI shells. This value is also significantly larger compared to the typical values of a few μG found in the diffuse HI gas from Zeeman splitting. We interpret this as the result of magnetic-field compression caused by the shell expansion. This study supports a scenario of molecular-cloud formation triggered by supersonic compression of cold magnetized HI gas from expanding interstellar bubbles.

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Dust polarization modelling at large scale over the northern Galactic cap using EBHIS and Planck data

Cited by 15 publications

References 66 publications

Maps of the Number of H i Clouds along the Line of Sight at High Galactic Latitude

Maps of the Number of H i Clouds along the Line of Sight at High Galactic Latitude

Statistical description of dust polarized emission from the diffuse interstellar medium

Compressed magnetized shells of atomic gas and the formation of the Corona Australis molecular cloud

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