تقرير
CLASS Observations of Atmospheric Cloud Polarization at Millimeter Wavelengths
| العنوان: | CLASS Observations of Atmospheric Cloud Polarization at Millimeter Wavelengths |
|---|---|
| المؤلفون: | Li, Yunyang, Appel, John W., Bennett, Charles L., Bustos, Ricardo, Chuss, David T., Cleary, Joseph, Couto, Jullianna Denes, Dahal, Sumit, Datta, Rahul, Dünner, Rolando, Eimer, Joseph R., Essinger-Hileman, Thomas, Harrington, Kathleen, Iuliano, Jeffrey, Marriage, Tobias A., Petroff, Matthew A., Reeves, Rodrigo A., Rostem, Karwan, Shi, Rui, Valle, Deniz A. N., Watts, Duncan J., Wolff, Oliver F., Wollack, Edward J., Xu, Zhilei |
| سنة النشر: | 2023 |
| المجموعة: | Astrophysics Physics (Other) |
| مصطلحات موضوعية: | Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, Physics - Atmospheric and Oceanic Physics |
| الوصف: | 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 (CLASS) experiment on Cerro Toco in the Atacama Desert of northern Chile, from 2016 to 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 $90^\circ$ 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 $3.90\pm0.06$, 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. Comment: 16 pages, 14 figures, submitted to ApJ |
| نوع الوثيقة: | Working Paper |
| URL الوصول: | http://arxiv.org/abs/2309.07221 |
| رقم الأكسشن: | edsarx.2309.07221 |
| قاعدة البيانات: | arXiv |
| الوصف غير متاح. |