Cosmology Large Angular Scale Surveyor: Difference between revisions

Revision as of 16:24, 6 March 2020

Revision as of 16:25, 6 March 2020

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CLASS is currently observing the sky in all four frequency bands. The CLASS 40 GHz telescope achieved first light on 8 May 2016 and began a roughly five-year survey in September 2016 after initial commissioning observations were complete. In early 2018, the first 90 GHz telescope was installed on the same mount as the 40 GHz telescope, achieving first light on 30 May 2018. In 2019, the dual-frequency 150/220 GHz telescope was deployed, along with a second telescope mount, and achieved first light on 21 September 2019.

CLASS has made a first detection of [[circular polarization]] from the atmosphere at a frequency of 40 GHz, which is in agreement with models of atmospheric circular polarization due to [[Zeeman effect|Zeeman splitting]] of [[Allotropes of oxygen|molecular oxygen]] in the presence of the Earth's magnetic field.<ref>{{Cite journal|last=Petroff|first=Matthew A.|last2=Eimer|first2=Joseph R.|last3=Harrington|first3=Kathleen|last4=Ali|first4=Aamir|last5=Appel|first5=John W.|last6=Bennett|first6=Charles L.|last7=Brewer|first7=Michael K.|last8=Bustos|first8=Ricardo|last9=Chan|first9=Manwei|last10=Chuss|first10=David T.|last11=Cleary|first11=Joseph|date=2020-01-30|title=Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: A First Detection of Atmospheric Circular Polarization at Q band|url=https://ui.adsabs.harvard.edu/link_gateway/2020ApJ...889..120P/doi:10.3847/1538-4357/ab64e2|journal=The Astrophysical Journal|volume=889|issue=2|pages=120|doi=10.3847/1538-4357/ab64e2|issn=1538-4357}}</ref> The atmospheric circular polarization is smoothly-varying over the sky, allowing it to be separated from celestial circular polarization. This has allowed CLASS to constrain celestial circular polarization at 40 GHz to be less than 1 μK at angular scales of 5 degrees and less than 4 μK at angular scales around 1 degree.<ref>{{Cite journal|last=Padilla|first=Ivan L.|last2=Eimer|first2=Joseph R.|last3=Li|first3=Yunyang|last4=Addison|first4=Graeme E.|last5=Ali|first5=Aamir|last6=Appel|first6=John W.|last7=Bennett|first7=Charles L.|last8=Bustos|first8=Ricardo|last9=Brewer|first9=Michael K.|last10=Chan|first10=Manwei|last11=Chuss|first11=David T.|date=2020-01-29|title=Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: A Measurement of Circular Polarization at 40 GHz|url=https://ui.adsabs.harvard.edu/link_gateway/2020ApJ...889..105P/doi:10.3847/1538-4357/ab61f8|journal=The Astrophysical Journal|volume=889|issue=2|pages=105|doi=10.3847/1538-4357/ab61f8|issn=1538-4357}}</ref> CLASSThis hasis improvedan improvement upon previous limits on circular polarization in the CMB by more than a factor of 100.<ref>{{Cite journal|last=Mainini|first=R.|last2=Minelli|first2=D.|last3=Gervasi|first3=M.|last4=Boella|first4=G.|last5=Sironi|first5=G.|last6=Baú|first6=A.|last7=Banfi|first7=S.|last8=Passerini|first8=A.|last9=Lucia|first9=A. De|last10=Cavaliere|first10=F.|date=2013-08|title=An improved upper limit to the CMB circular polarization at large angular scales|url=https://doi.org/10.1088%2F1475-7516%2F2013%2F08%2F033|journal=Journal of Cosmology and Astroparticle Physics|language=en|volume=2013|issue=08|pages=033–033|doi=10.1088/1475-7516/2013/08/033|issn=1475-7516}}</ref><ref>{{Cite journal|last=Nagy|first=J. M.|last2=Ade|first2=P. A. R.|last3=Amiri|first3=M.|last4=Benton|first4=S. J.|last5=Bergman|first5=A. S.|last6=Bihary|first6=R.|last7=Bock|first7=J. J.|last8=Bond|first8=J. R.|last9=Bryan|first9=S. A.|last10=Chiang|first10=H. C.|last11=Contaldi|first11=C. R.|date=2017-08|title=A New Limit on CMB Circular Polarization from SPIDER|url=https://doi.org/10.3847%2F1538-4357%2Faa7cfd|journal=The Astrophysical Journal|language=en|volume=844|issue=2|pages=151|doi=10.3847/1538-4357/aa7cfd|issn=0004-637X}}</ref>

== See also ==