Modelling and simulation of large-scale polarized dust emission over the southern Galactic cap using the GASS Hi data

Ghosh, T.; Boulanger, F.; Martín, P. G.; Bracco, A.; Vansyngel, F.; Aumont, J.; Bock, J. J.; Doré, O.; Haud, U.; Kalberla, P. M. W.; Serra, P.

doi:10.1051/0004-6361/201629829

Cited by 41 publications

(48 citation statements)

References 85 publications

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“…First, the T map, which is added to the polarization part through the parameter ρ, has a filamentary structure and thus is anisotropic. This amounts to adding an extra polarization layer that is perfectly aligned with the filamentary structure of the matter and is similar to what is carried out by Ghosh et al (2017) for their cold neutral medium map. Second, the factor f breaks the symmetry between E and B, whereas the power is expected to be equally distributed between E and B modes in the case of isotropic turbulence (Caldwell et al 2017).…”

Section: Introducing Te Correlation and E-b Asymmetrymentioning

confidence: 83%

“…It overcomes the difficulty of generating realizations of the turbulent component of the magnetic field in three dimensions over the celestial sphere. Ghosh et al (2017) uses Hi data to associate the layers with different phases of the ISM, each of which provide a different intensity map. On the contrary, in the simulations presented in this paper, like in PXLIV, the term S i (ν) in Eqs.…”

Section: Astrophysical Frameworkmentioning

confidence: 99%

“…The factor f 2 = 0.55 is close to the value of R BB = 0.48 (Table 1). Within this model, unlike for that of Ghosh et al (2017), the T E correlation accounts for only a small part of the E-B asymmetry. Figure 4 shows ratios between the different power spectra of the simulated maps.…”

Section: Matching Planck Power Spectramentioning

confidence: 99%

“…In this paper, we extend their work to produce Stokes maps that fit dust polarization power spectra including the T E correlation and the T T/EE and EE/BB power ratios at high and intermediate Galactic latitudes. In a companion paper Ghosh et al (2017), the dust polarization of the southern sky region with the lowest dust column density is modeled using Hi observations and astrophysical insight to constrain their model parameters. In essence, our approach is more mathematical but it allows us to model dust polarization over a larger fraction of the sky.…”

Section: Introductionmentioning

confidence: 99%

“…Second, the factor f breaks the symmetry between E and B, whereas the power is expected to be equally distributed between E and B modes in the case of isotropic turbulence (Caldwell et al 2017). Through the parameter f , the random component of B is anisotropic in all layers and everywhere on the sky, unlike in Ghosh et al (2017) where anisotropy is introduced in only one layer.…”

Section: Introducing Te Correlation and E-b Asymmetrymentioning

confidence: 99%

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Statistical simulations of the dust foreground to cosmic microwave background polarization

Vansyngel

Boulanger

Ghosh

et al. 2017

A&A

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101

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The characterization of the dust polarization foreground to the cosmic microwave background (CMB) is a necessary step toward the detection of the B-mode signal associated with primordial gravitational waves. We present a method to simulate maps of polarized dust emission on the sphere that is similar to the approach used for CMB anisotropies. This method builds on the understanding of Galactic polarization stemming from the analysis of Planck data. It relates the dust polarization sky to the structure of the Galactic magnetic field and its coupling with interstellar matter and turbulence. The Galactic magnetic field is modeled as a superposition of a mean uniform field and a Gaussian random (turbulent) component with a power-law power spectrum of exponent α M . The integration along the line of sight carried out to compute Stokes maps is approximated by a sum over a small number of emitting layers with different realizations of the random component of the magnetic field. The model parameters are constrained to fit the power spectra of dust polarization EE, BB, and T E measured using Planck data. We find that the slopes of the E and B power spectra of dust polarization are matched for α M = −2.5, an exponent close to that measured for total dust intensity but larger than the Kolmogorov exponent −11/3. The model allows us to compute multiple realizations of the Stokes Q and U maps for different realizations of the random component of the magnetic field, and to quantify the variance of dust polarization spectra for any given sky area outside of the Galactic plane. The simulations reproduce the scaling relation between the dust polarization power and the mean total dust intensity including the observed dispersion around the mean relation. We also propose a method to carry out multifrequency simulations, including the decorrelation measured recently by Planck, using a given covariance matrix of the polarization maps. These simulations are well suited to optimize component separation methods and to quantify the confidence with which the dust and CMB B-modes can be separated in present and future experiments. We also provide an astrophysical perspective on our phenomenological modeling of the dust polarization spectra.

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Section: Introducing Te Correlation and E-b Asymmetrymentioning

confidence: 83%

Section: Astrophysical Frameworkmentioning

confidence: 99%

Section: Matching Planck Power Spectramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introducing Te Correlation and E-b Asymmetrymentioning

confidence: 99%

See 3 more Smart Citations

Statistical simulations of the dust foreground to cosmic microwave background polarization

Vansyngel

Boulanger

Ghosh

et al. 2017

A&A

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101

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H i anisotropies associated with radio-polarimetric filaments

Kalberla¹,

Kerp²,

Haud

et al. 2017

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Context. LOFAR detected toward 3C 196 linear polarization structures which were found subsequently to be closely correlated with cold filamentary H i structures. The derived direction-dependent H i power spectra revealed marked anisotropies for narrow ranges in velocity, sharing the orientation of the magnetic field as expected for magneto hydrodynamical (MHD) turbulence. Aims. Using the Galactic portion of the Effelsberg-Bonn H i Survey (EBHIS) we continue our study of such anisotropies in the H i distribution in direction of two WSRT fields, Horologium and Auriga; both are well known for their prominent radio-polarimetric depolarization canals. At 349 MHz the observed pattern in total intensity is insignificant but polarized intensity and polarization angle show prominent ubiquitous structures with so far unknown origin. Methods. Apodizing the H i survey data by applying a rotational symmetric 50% Tukey window, we derive average and position angle dependent power spectra. We fit power laws and characterize anisotropies in the power distribution. We used a Gaussian analysis to determine relative abundances for the cold and warm neutral medium. Results. For the analyzed radio-polarimetric targets significant anisotropies are detected in the H i power spectra; their position angles are aligned to the prominent depolarization canals, initially detected by WSRT. H i anisotropies are associated with steep power spectra. Steep power spectra, associated with cold gas, are detected also in other fields. Conclusions. Radio-polarimetric depolarization canals are associated with filamentary H i structures that belong to the cold neutral medium (CNM). Anisotropies in the CNM are in this case linked to a steepening of the power-spectrum spectral index, indicating that phase transitions in a turbulent medium occur on all scales. Filamentary H i structures, driven by thermal instabilities, and radiopolarimetric filaments are associated with each other. The magneto-ionic medium that causes the radio-polarimetric filaments is probably wrapped around the H i.

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Planck2018 results

Akrami

Ashdown

Aumont

et al. 2020

A&A

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141

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The study of polarized dust emission has become entwined with the analysis of the cosmic microwave background (CMB) polarization in the quest for the curl-like B-mode polarization from primordial gravitational waves and the low-multipole E-mode polarization associated with the reionization of the Universe. We used the new Planck PR3 maps to characterize Galactic dust emission at high latitudes as a foreground to the CMB polarization and use end-to-end simulations to compute uncertainties and assess the statistical significance of our measurements. We present Planck EE, BB, and T E power spectra of dust polarization at 353 GHz for a set of six nested high-Galactic-latitude sky regions covering from 24 to 71 % of the sky. We present power-law fits to the angular power spectra, yielding evidence for statistically significant variations of the exponents over sky regions and a difference between the values for the EE and BB spectra, which for the largest sky region are α EE = −2.42 ± 0.02 and α BB = −2.54 ± 0.02, respectively. The spectra show that the T E correlation and E/B power asymmetry discovered by Planck extend to low multipoles that were not included in earlier Planck polarization papers due to residual data systematics. We also report evidence for a positive T B dust signal. Combining data from Planck and WMAP, we have determined the amplitudes and spectral energy distributions (SEDs) of polarized foregrounds, including the correlation between dust and synchrotron polarized emission, for the six sky regions as a function of multipole. This quantifies the challenge of the component-separation procedure that is required for measuring the low-reionization CMB E-mode signal and detecting the reionization and recombination peaks of primordial CMB B modes. The SED of polarized dust emission is fit well by a singletemperature modified black-body emission law from 353 GHz to below 70 GHz. For a dust temperature of 19.6 K, the mean dust spectral index for dust polarization is β P d = 1.53 ± 0.02. The difference between indices for polarization and total intensity is β P d − β I d = 0.05 ± 0.03. By fitting multi-frequency cross-spectra between Planck data at 100, 143, 217, and 353 GHz, we examine the correlation of the dust polarization maps across frequency. We find no evidence for a loss of correlation and provide lower limits to the correlation ratio that are tighter than values we derive from the correlation of the 217-and 353-GHz maps alone. If the Planck limit on decorrelation for the largest sky region applies to the smaller sky regions observed by sub-orbital experiments, then frequency decorrelation of dust polarization might not be a problem for CMB experiments aiming at a primordial B-mode detection limit on the tensor-to-scalar ratio r 0.01 at the recombination peak. However, the Planck sensitivity precludes identifying how difficult the component-separation problem will be for more ambitious experiments targeting lower limits on r.

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Modelling and simulation of large-scale polarized dust emission over the southern Galactic cap using the GASS Hi data

Cited by 41 publications

References 85 publications

Statistical simulations of the dust foreground to cosmic microwave background polarization

Statistical simulations of the dust foreground to cosmic microwave background polarization

H i anisotropies associated with radio-polarimetric filaments

Planck2018 results

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