Measurements of Tropospheric Ice Clouds with a Ground-based CMB Polarization Experiment, POLARBEAR

S. Takakura, M. A.O. Aguilar-Faundez, Y. Akiba, K. Arnold, C. Baccigalupi, D. Barron, D. Beck, F. Bianchini, D. Boettger, J. Borrill, K. Cheung, Y. Chinone, T. Elleflot, J. Errard, G. Fabbian, C. Feng, N. Goeckner-Wald, T. Hamada, M. Hasegawa, M. HazumiL. Howe, D. Kaneko, N. Katayama, B. Keating, R. Keskitalo, T. Kisner, N. Krachmalnicoff, A. Kusaka, A. T. Lee, L. N. Lowry, F. T. Matsuda, A. J. May, Y. Minami, M. Navaroli, H. Nishino, L. Piccirillo, D. Poletti, G. Puglisi, C. L. Reichardt, Y. Segawa, M. Silva-Feaver, P. Siritanasak, A. Suzuki, O. Tajima, S. Takatori, D. Tanabe, G. P. Teply, C. Tsai

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The polarization of the atmosphere has been a long-standing concern for ground-based experiments targeting cosmic microwave background (CMB) polarization. Ice crystals in upper tropospheric clouds scatter thermal radiation from the ground and produce a horizontally polarized signal. We report a detailed analysis of the cloud signal using a ground-based CMB experiment, Polarbear, located at the Atacama desert in Chile and observing at 150 GHz. We observe horizontally polarized temporal increases of low-frequency fluctuations ("polarized bursts," hereafter) of ≲0.1 K when clouds appear in a webcam monitoring the telescope and the sky. The hypothesis of no correlation between polarized bursts and clouds is rejected with >24σ statistical significance using three years of data. We consider many other possibilities including instrumental and environmental effects, and find no reasons other than clouds that can explain the data better. We also discuss the impact of the cloud polarization on future ground-based CMB polarization experiments.

    Original languageEnglish
    Article number102
    JournalAstrophysical Journal
    Volume870
    Issue number2
    Early online date10 Jan 2019
    DOIs
    Publication statusPublished - 2019

    Keywords

    • atmospheric effects
    • cosmic background radiation
    • cosmology: observations
    • polarization
    • scattering

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