Polarization of Light From Distant Stars by Interstellar Medium

Hiltner, W. A.

doi:10.1126/science.109.2825.165

Cited by 318 publications

(166 citation statements)

References 2 publications

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“…Early observations by Hiltner (1949);Hall (1949) and later by Heiles (2000) demonstrated that starlight emission in the optical domain was polarized, and therefore we can expect the thermal dust emission at millimeter wavelengths also to be polarized. This was confirmed by the Archeops observations at 353 GHz (Ponthieu et al 2005) that yielded a polarization fraction of about 10% in the Galactic plane.…”

Section: Thermal Dustmentioning

confidence: 99%

Joint 3D modelling of the polarized Galactic synchrotron and thermal dust foreground diffuse emission

Fauvet

Macías-Pérez

Aumont

et al. 2011

A&A

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Aims. We present for the first time a coherent model of the polarized Galactic synchrotron and thermal dust emissions that are likely to form the predominant diffuse foregrounds for measuring the polarized CMB fluctuations by the Planck satellite mission. Methods. We produced 3D models of the Galactic magnetic field including regular and turbulent components, and of the distribution of matter in the Galaxy including relativistic electron and dust grain components. By integrating along the line of sight, we constructed maps of the polarized Galactic synchrotron and thermal dust emission for each of these models and compared them to currently available data. We consider the 408 MHz all-sky continuum survey, the 23 GHz band of the Wilkinson Microwave Anisotropy Probe, and the 353 GHz Archeops data. Results. The best-fit parameters obtained are consistent with previous estimates in the literature based only on synchrotron emission and pulsar rotation measurements and this allows us to reproduce the large-scale features observed in the data. Unmodeled local Galactic structures and the effect of turbulence make it difficult to accurately reconstruct observations in the Galactic plane. Conclusions. Finally, using the best-fit model we are able to estimate the expected polarized foreground contamination at the Planck frequency bands. For the CMB bands, 70, 100, 143 and 217 GHz, at high Galactic latitudes although the CMB signal dominates in general, a significant foreground contribution is expected at large angular scales. In particular, this contribution will dominate the CMB signal for the B modes expected from realistic models of a background of primordial gravitational waves.

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Section: Thermal Dustmentioning

confidence: 99%

Joint 3D modelling of the polarized Galactic synchrotron and thermal dust foreground diffuse emission

Fauvet

Macías-Pérez

Aumont

et al. 2011

A&A

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“…The notion that the grains can be aligned with respect to the magnetic field can be traced back to the discovery of starlight polarization by Hall (1949) and Hiltner (1949), which arises from interstellar grains. Historically, the theory of the grain alignment was primarily developed to explain the interstellar polarization, but grain alignment is a much more widespread phenomenon (see Lazarian 2007 for a review).…”

Section: Introductionmentioning

confidence: 99%

Grain Alignment and Polarized Emission from Magnetized T Tauri Disks

Cho

Lazarían

2007

ApJ

129

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The structure of magnetic fields within protostellar disks may be studied via polarimetry provided that grains are aligned with respect to the magnetic field within the disks. We explore the alignment of dust grains by radiative torque in T Tauri disks and provide predictions for polarized emission for disks viewed at different wavelengths and viewing angles. We show that the alignment is especially efficient in the outer parts of the disks. In the presence of a magnetic field, these aligned grains produce polarized emission in infrared wavelengths. We consider a simple disk model and provide predictions for polarization that are available to the present-day instruments that do not resolve the disks and will be available to future instruments that will resolve the disks. We find that the polarized emission drops for wavelengths shorter than $10 m. Between $10 and $100 m, the polarized emission is dominated by the emission from the surface layer, and the degree of polarization can be as large as $10% for unresolved disks. We find that the degree of polarization at these wavelengths is very sensitive to the size distribution of dust grains in the disk surface layer, which should allow for the testing of the predicted grain-size distributions. The degree of polarization in the far-infrared/ submillimeter wavelengths is sensitive to the size distribution of dust grains in the disk interior. When we take a MathisRumpl-Nordsieck-type distribution with maximum grain size of 500-1000 m, the degree of polarization is around the 2%-3% level at wavelengths larger than $100 m. Our study indicates that multifrequency infrared polarimetric studies of protostellar disks can provide good insights into the details of their magnetic structure.

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“…The polarized light measured by ExPo not only contains the polarized light coming from the circumstellar environment, but also telescope polarization (Miller 1963) and interstellar polarization (Hiltner 1949). Moreover, any small difference between the beamsplitter transmission coefficients (T A , T B ) or the FLC transmission coefficients (T L , T R ) introduces an artificial polarization signature.…”

Section: Instrumental Polarizationmentioning

confidence: 99%

Data-reduction techniques for high-contrast imaging polarimetry

Cánovas

Rodenhuis

Jeffers

et al. 2011

A&A

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Context. Imaging polarimetry is a powerful tool for detecting and characterizing exoplanets and circumstellar environments. Polarimetry allows a separation of the light coming from an unpolarized source such as a star and the polarized source such as a planet or a protoplanetary disk. Future facilities like SPHERE at the VLT or EPICS at the E-ELT will incorporate imaging polarimetry to detect exoplanets. The Extreme Polarimeter (ExPo) is a dual-beam imaging polarimeter that can currently reach contrast ratios of 10 5 , enough to characterize circumstellar environments. Aims. We present the data-reduction steps for a dual-beam imaging polarimeter that can reach contrast ratios of 10 5 . Methods. The data obtained with ExPo at the William Herschel Telescope (WHT) are analyzed. Instrumental artifacts and noise sources are discussed for an unpolarized star and for a protoplanetary disk (AB Aurigae).Results. The combination of fast modulation and dual-beam techniques allows us to minimize instrumental artifacts. A proper data processing and alignment of the images is fundamental when dealing with high contrasts. Imaging polarimetry proves to be a powerful method to resolve circumstellar environments even without a coronagraph mask or an adaptive optics system.

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Polarization of Light From Distant Stars by Interstellar Medium

Cited by 318 publications

References 2 publications

Joint 3D modelling of the polarized Galactic synchrotron and thermal dust foreground diffuse emission

Joint 3D modelling of the polarized Galactic synchrotron and thermal dust foreground diffuse emission

Grain Alignment and Polarized Emission from Magnetized T Tauri Disks

Data-reduction techniques for high-contrast imaging polarimetry

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