Radiative transfer with POLARIS

Reißl, Stefan; Wolf, S.; Brauer, Robert

doi:10.1051/0004-6361/201424930

Cited by 145 publications

(181 citation statements)

References 91 publications

(123 reference statements)

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“…We apply the three-dimensional continuum RT code POLARIS (POLArized RadIation Simulator, Reissl et al 2016;Brauer et al 2017). It solves the radiative transfer problem self-consistently with the Monte Carlo method.…”

Section: The Rt Code Polarismentioning

confidence: 99%

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GG Tauri A: dark shadows on the ringworld

Brauer¹,

Pantin²,

Folco³

et al. 2019

A&A

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Context. With its high complexity, large size, and close distance, the ringworld around GG Tau A is an appealing case to study the formation and evolution of protoplanetary disks around multiple star systems. However, investigations with radiative transfer models are usually neglecting the influence of the circumstellar dust around the individual stars. Aims. We investigate how circumstellar disks around the stars of GG Tau A are influencing the emission that is scattered at the circumbinary disk and if constraints on these circumstellar disks can be derived. Methods. We perform radiative transfer simulations with the code POLARIS to obtain spectral energy distributions and emission maps in the H-Band (near-infrared). Subsequently, we compare them with observations to achieve our aims. Results. We studied the ratio of polarized intensity at different locations in the circumbinary disk and conclude that the observed scattered-light near-infrared emission is best reproduced, if the circumbinary disk lies in the shadow of at least two co-planar circumstellar disks surrounding the central stars. This implies that the inner wall of the circumbinary disk is strongly obscured around the midplane, while the observed emission is actually dominated by the most upper disk layers. In addition, the inclined dark lane ("gap") on the western side of the circumbinary disk, which is a stable (non rotating) feature since ∼20 yr, can only be explained by the self-shadowing of a misaligned circumstellar disk surrounding one of the two components of the secondary close-binary star GG Tau Ab.A&A proofs: manuscript no. gg_tau tions (Sect. 2). Subsequently, we introduce the model of GG Tau A, which includes the inner circumstellar disks as well as the surrounding circumbinary disk (Sect. 3). Then, we present our results and investigate the impact of the circumstellar disks on the emission of the circumbinary disk (in Sect. 4). Finally, we summarize our conclusions in Sect. 5.

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Section: The Rt Code Polarismentioning

confidence: 99%

“…Even some single stars show similar effects (e.g., RXJ1604.3-2130, Pinilla et al 2018). We perform the radiative transfer simulations with the RT code POLARIS (Reissl et al 2016;Brauer et al 2017), which was recently updated to consider complex structures of circumstellar disks (Brauer et al in prep. ).…”

Section: Introductionmentioning

confidence: 99%

GG Tauri A: dark shadows on the ringworld

Brauer¹,

Pantin²,

Folco³

et al. 2019

A&A

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“…To investigate if the mechanism would work in the much denser circumstellar environment we need to compare the alignment timescale, given by the Larmor precession timescale, with the timescale set by gas-dust interaction (e.g. Hoang & Lazarian 2009;Reissl et al 2016). This comparison yields a lower limit for the magnetic field strength that, following Hoang & Lazarian (2009), can be written as:…”

Section: Dust Polarization Of Clump Cmentioning

confidence: 99%

Magnetically aligned dust and SiO maser polarisation in the envelope of the red supergiant VY Canis Majoris

Vlemmings

Khouri

Martí-Vidal

et al. 2017

A&A

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Aims. Polarization observations of circumstellar dust and molecular (thermal and maser) lines provide unique information about dust properties and magnetic fields in circumstellar envelopes of evolved stars. Methods. We use Atacama Large Millimeter/submillimeter Array Band 5 science verification observations of the red supergiant VY CMa to study the polarization of SiO thermal/masers lines and dust continuum at ∼ 1.7 mm wavelength. We analyse both linear and circular polarization and derive the magnetic field strength and structure, assuming the polarization of the lines originates from the Zeeman effect, and that of the dust originates from aligned dust grains. We also discuss other effects that could give rise to the observed polarization. Results. We detect, for the first time, significant polarization (∼ 3%) of the circumstellar dust emission at millimeter wavelengths. The polarization is uniform with an electric vector position angle of ∼ 8• . Varying levels of linear polarization are detected for the J = 4−3 28 SiO v = 0, 1, 2, and 29 SiO v = 0, 1 lines, with the strongest polarization fraction of ∼ 30% found for the 29 SiO v = 1 maser. The linear polarization vectors rotate with velocity, consistent with earlier observations. We also find significant (up to ∼ 1%) circular polarization in several lines, consistent with previous measurements. We conclude that the detection is robust against calibration and regular instrumental errors, although we cannot yet fully rule out non-standard instrumental effects. Conclusions. Emission from magnetically aligned grains is the most likely origin of the observed continuum polarization. This implies that the dust is embedded in a magnetic field > 13 mG. The maser line polarization traces the magnetic field structure. The magnetic field in the gas and dust is consistent with an approximately toroidal field configuration, but only higher angular resolution observations will be able to reveal more detailed field structure. If the circular polarization is due to Zeeman splitting, it indicates a magnetic field strength of ∼ 1 − 3 Gauss, consistent with previous maser observations.

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“…We apply the three-dimensional continuum RT code POLARIS (POLArized RadIation Simulator, Reissl et al 2016). This solves the radiative transfer problem self-consistently with the Monte Carlo method, and it considers magnetic fields as well as various dust grain alignment mechanisms.…”

Section: Radiative Transfermentioning

confidence: 99%

“…Furthermore, we vary selected parameters, such as dust grain size and density distribution, to cover different kinds of Bok globules and investigate the impact of such parameters on the answer of our key question. Based on our model of a Bok globule, we perform continuum radiative transfer simulations in the submm/mm regime with the radiative transfer code POLARIS (POLArized RadIation Simulator, Reissl et al 2016) which is able to consider magnetic fields and the dust grain alignment mechanisms mentioned above. From POLARIS, we obtain intensity and polarization maps to investigate a potential decrease in the degree of polarization.…”

Section: Introductionmentioning

confidence: 99%

On the origins of polarization holes in Bok globules

Brauer¹,

Wolf²,

Reißl³

2016

A&A

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Context. Polarimetric observations of Bok globules frequently show a decrease in the degree of polarization towards their central dense regions (polarization holes). This behaviour is usually explained with increased disalignment owing to high density and temperature, or insufficient angular resolution of a possibly complex magnetic field structure. Aims. We investigate whether a significant decrease in polarized emission of dense regions in Bok globules is possible under certain physical conditions. For instance, we evaluate the impact of optical depth effects and various properties of the dust phase. Methods. We use radiative transfer modelling to calculate the temperature structure of an analytical Bok globule model and simulate the polarized thermal emission of elongated dust grains. For the alignment of the dust grains, we consider a magnetic field and include radiative torque and internal alignment. Results. Besides the usual explanations, selected conditions of the temperature and density distribution, the dust phase and the magnetic field are also able to significantly decrease the polarized emission of dense regions in Bok globules. Taking submm/mm grains and typical column densities of existing Bok globules into consideration, the optical depth is high enough to decrease the degree of polarization by up to ∆P ∼ 10%. If limited to the densest regions, dust grain growth to submm/mm size and accumulated graphite grains decrease the degree of polarization by up to ∆P ∼ 10% and ∆P ∼ 5%, respectively. However, the effect of the graphite grains occurs only if they do not align with the magnetic field.

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Radiative transfer with POLARIS

Cited by 145 publications

References 91 publications

GG Tauri A: dark shadows on the ringworld

GG Tauri A: dark shadows on the ringworld

Magnetically aligned dust and SiO maser polarisation in the envelope of the red supergiant VY Canis Majoris

On the origins of polarization holes in Bok globules

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