Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: A First Detection of Atmospheric Circular Polarization at Q band

Petroff, Matthew A.; Eimer, Joseph; Harrington, Kathleen; Ali, Aamir; Appel, John W.; Bennett, C. L.; Brewer, Michael K.; Bustos, R.; Chan, Manwei; Chuss, David T.; Cleary, Joseph; Couto, Jullianna Denes; Dahal, Sumit; Dünner, Rolando; Essinger-Hileman, Thomas; Rojas, Pedro Fluxá; Gothe, D.A.; Iuliano, Jeffrey; Marriage, Tobias A.; Miller, Nathan J.; Núñez, Carolina; Padilla, Ivan L.; Parker, Lucas; Reeves, R.; Rostem, Karwan; Valle, Deniz Augusto Nunes; Watts, Duncan J.; Weiland, J. L.; Wollack, Edward J.; Xu, Zhilei

doi:10.3847/1538-4357/ab64e2

Cited by 14 publications

(10 citation statements)

References 73 publications

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“…12 Whether the higher V white noise is responsible for the lower knee frequencies depends on whether the red noise is uncorrelated with the V modulation function or if it represents on-sky signal. † † While CLASS has made the first detection of continuum circular polarization due to Zeeman splitting of oxygen in the atmosphere, 13,14 we do not expect this component to have significant random fluctuations, and there are no other known sources of V fluctuations on sky.…”

Section: Resultsmentioning

confidence: 74%

Long-timescale stability in CMB observations at multiple frequencies using front-end polarization modulation

Cleary¹,

Datta²

2022

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XI

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The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array observing the Cosmic Microwave Background (CMB) at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the CMB polarization on the largest angular scales to constrain the inflationary tensor-to-scalar ratio and the optical depth due to reionization. To achieve the long time-scale stability necessary for this measurement from the ground, CLASS utilizes a front-end, variable-delay polarization modulator on each telescope. Here we report on the improvements in stability afforded by front-end modulation using data across all four CLASS frequencies. Across one month of modulated linear polarization data in 2021, CLASS achieved median knee frequencies of 9. 1, 29.1, 20.4, and 36.4 mHz for the 40, 90, 150, and 220 GHz observing bands. The knee frequencies are approximately an order of magnitude lower than achieved via CLASS pair-differencing orthogonal detector pairs without modulation.

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Section: Resultsmentioning

confidence: 74%

Long-timescale stability in CMB observations at multiple frequencies using front-end polarization modulation

Cleary¹,

Datta²

2022

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XI

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“…In the Rayleigh scattering regime, circular polarization from directly scattering atmospheric circular emission (Petroff et al 2020) is negligible due to parity. For Mie scattering, the coupling between linear and circular polarization (Bohren & Huffman 1983) can convert the linear polarization induced by preceding scatterings into circular polarization (Kawata 1978;Slonaker et al 2005).…”

Section: Mie Scatteringmentioning

confidence: 99%

“…Despite being mostly unpolarized (Battistelli et al 2012), the atmosphere is known to be circularly polarized due to the Zeeman effect from the magnetic dipole transition of the oxygen molecules in the Earth's magnetic field (Lenoir 1967(Lenoir , 1968Petroff et al 2020). This is a systematic issue for experiments with polarization modulation (Chuss et al 2012;Nagy et al 2017) and presents a challenge to ground-based pursuits of astrophysical/cosmological circular polarization signatures (King & Lubin 2016;Padilla et al 2020;Eimer et al 2023).…”

Section: Introductionmentioning

confidence: 99%

CLASS Observations of Atmospheric Cloud Polarization at millimeter Wavelengths

Li 李,

Appel,

Bennett

et al. 2023

ApJ

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The dynamic atmosphere imposes challenges to ground-based cosmic microwave background observation, especially for measurements on large angular scales. The hydrometeors in the atmosphere, mostly in the form of clouds, scatter the ambient thermal radiation and are known to be the main linearly polarized source in the atmosphere. This scattering-induced polarization is significantly enhanced for ice clouds due to the alignment of ice crystals under gravity, which are also the most common clouds seen at the millimeter-astronomy sites at high altitudes. This work presents a multifrequency study of cloud polarization observed by the Cosmology Large Angular Scale Surveyor experiment on Cerro Toco in the Atacama Desert of northern Chile, from 2016–2022, at the frequency bands centered around 40, 90, 150, and 220 GHz. Using a machine-learning-assisted cloud classifier, we made connections between the transient polarized emission found in all four frequencies with the clouds imaged by monitoring cameras at the observing site. The polarization angles of the cloud events are found to be mostly 90° from the local meridian, which is consistent with the presence of horizontally aligned ice crystals. The 90 and 150 GHz polarization data are consistent with a power law with a spectral index of 3.90 ± 0.06, while an excess/deficit of polarization amplitude is found at 40/220 GHz compared with a Rayleigh scattering spectrum. These results are consistent with Rayleigh-scattering-dominated cloud polarization, with possible effects from supercooled water absorption and/or Mie scattering from a population of large cloud particles that contribute to the 220 GHz polarization.

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“…Cosmological birefringence has nowadays attracted a renewed interest, following its claimed detection on Planck legacy data [127]. Cosmic birefringence can also manifest itself due to Euler-Heisenberg photon-photon forward scattering that produces circular polarized CMB photons [128,129] for which new observational constraints have recently been obtained [130,131]. For other measurable effects which can be used to test the NEDs see e.g.…”

Section: Neds and Gravity/cmt Holographymentioning

confidence: 99%

Introductory Notes on Non-linear Electrodynamics and its Applications

Sorokin¹

2021

Preprint

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In 1934 Born and Infeld constructed the first non-linear generalization of Maxwell's electrodynamics that turned out to be a remarkable theory in many respects. In 1936 Heisenberg and Euler computed an effective action describing non-linear corrections to Maxwell's theory due to quantum electron-positron one-loop effects. Since then, these and a variety of other models of non-linear electrodynamics proposed in the course of decades have been extensively studied and used in a wide range of areas of theoretical physics including string theory, gravity, cosmology and condensed matter (CMT). In these notes I will overview general properties of non-linear electrodynamics and particular models which are distinguished by their symmetries and physical properties, such as a recently discovered unique non-linear modification of Maxwell's electrodynamics which is conformal and duality invariant. I will also sketch how non-linear electromagnetic effects may manifest themselves in physical phenomena (such as vacuum birefringence), in properties of gravitational objects (e.g. charged black holes) and in the evolution of the universe, and can be used, via gravity/CMT holography, for the description of properties of certain conducting and insulating materials.

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Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: A First Detection of Atmospheric Circular Polarization at Q band

Cited by 14 publications

References 73 publications

Long-timescale stability in CMB observations at multiple frequencies using front-end polarization modulation

Long-timescale stability in CMB observations at multiple frequencies using front-end polarization modulation

CLASS Observations of Atmospheric Cloud Polarization at millimeter Wavelengths

Introductory Notes on Non-linear Electrodynamics and its Applications

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