Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: A Measurement of Circular Polarization at 40 GHz

Abstract

We report circular polarization measurements from the first two years of observation with the 40 GHz polarimeter of the Cosmology Large Angular Scale Surveyor (CLASS). CLASS is conducting a multi-frequency survey covering 75% of the sky from the Atacama Desert designed to measure the cosmic microwave background (CMB) linear E and B polarization on angular scales $1^{\circ }\lesssim \theta \le 90^{\circ }$, corresponding to a multipole range of $2\le \ell \lesssim 200$. The modulation technology enabling measurements of linear polarization at the largest angular scales from the ground, the Variable-delay Polarization Modulator, is uniquely designed to provide explicit sensitivity to circular polarization (Stokes $V$). We present a first detection of circularly polarized atmospheric emission at 40 GHz that is well described by a dipole with an amplitude of $124\pm 4\mu \mathrm{K}$ when observed at an elevation of $45^{\circ }$, and discuss its potential impact as a foreground to CMB experiments. Filtering the atmospheric component, CLASS places a 95% C.L. upper limit of $0.4{\mu \mathrm{K}}^2$ to $13.5{\mu \mathrm{K}}^2$ on $\ell (\ell +1)C_{\ell }^{VV}/(2\pi )$ between $1\le \ell \le 120$, representing a two-orders-of-magnitude improvement over previous limits.

8 pages, 5 figures

References in corpus (36)

• The NumPy array: a structure for efficient numerical computation
• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• Efficient Computation of CMB anisotropies in closed FRW models
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results
• A measurement by BOOMERANG of multiple peaks in the angular power spectrum of the cosmic microwave background
• Detection of Polarization in the Cosmic Microwave Background using DASI
• BICEP2 / Keck Array x: Constraints on Primordial Gravitational Waves using Planck, WMAP, and New BICEP2/Keck Observations through the 2015 Season
• Fast estimation of polarization power spectra using correlation functions
• The Atacama Cosmology Telescope: Two-Season ACTPol Spectra and Parameters
• Measurements of the Temperature and E-Mode Polarization of the CMB from 500 Square Degrees of SPTpol Data
• CLASS: The Cosmology Large Angular Scale Surveyor
• The Atacama Cosmology Telescope: Data Characterization and Map Making
• Large Angular Scale Polarization of the Cosmic Microwave Background and the Feasibility of its Detection
• The Cosmology Large Angular Scale Surveyor
• Generation of circular polarization of the CMB
• Is the Cosmic Microwave Background Circularly Polarized?
• The Cosmology Large Angular Scale Surveyor (CLASS): 40 GHz optical design
• Properties of a Variable-delay Polarization Modulator
• A New Limit on CMB Circular Polarization from SPIDER
• Circular Polarization of the CMB: A probe of the First stars
• A Projected Estimate of the Reionization Optical Depth Using the CLASS Experiment's Sample-Variance Limited E-Mode Measurement
• The Cosmology Large Angular Scale Surveyor (CLASS): 38 GHz detector array of bolometric polarimeters
• Polarization of the Atmosphere as a Foreground for Cosmic Microwave Background Polarization Experiments
• The V-mode polarization of the Cosmic Microwave Background
• An improved upper limit to the CMB circular polarization at large angular scales
• Circular polarization of the CMB: Foregrounds and detection prospects
• On-sky performance of the CLASS Q-band telescope
• Exploring circular polarization in the CMB due to conventional sources of cosmic birefringence
• Circular polarization of the cosmic microwave background from vector and tensor perturbations
• Recovery of Large Angular Scale CMB Polarization for Instruments Employing Variable-delay Polarization Modulators
• Measuring the Largest Angular Scale CMB B-mode Polarization with Galactic Foregrounds on a Cut Sky
• New probe of magnetic fields in the prereionization epoch. I. Formalism
• Circular dichroism, magnetic knots and the spectropolarimetry of the Cosmic Microwave Background
• Circular polarization in a spherical basis
• A template of atmospheric O2 circularly polarized emission for CMB experiments
• On the CMB circular polarization. I. The Cotton-Mouton effect

Cited by in corpus (13)

• Early Dark Energy Does Not Restore Cosmological Concordance
• Four-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: On-sky Receiver Performance at 40, 90, 150, and 220 GHz Frequency Bands
• Probing Lorentz-violating electrodynamics with CMB polarization
• Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: 40 GHz Telescope Pointing, Beam Profile, Window Function, and Polarization Performance
• Framework for analysis of next generation, polarised CMB data sets in the presence of galactic foregrounds and systematic effects
• Two Year Cosmology Large Angular Scale Surveyor (CLASS) Observations: Long Timescale Stability Achieved with a Front-End Variable-delay Polarization Modulator at 40 GHz
• Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: A First Detection of Atmospheric Circular Polarization at Q Band
• CMB polarization as a tool to constrain the optical properties of the Universe
• Circular polarization of cosmic photons due to their interactions with Sterile neutrino dark matter
• A Simulation-Based Method for Correcting Mode Coupling in CMB Angular Power Spectra
• Cosmology Large Angular Scale Surveyor (CLASS): 90 GHz Telescope Pointing, Beam Profile, Window Function, and Polarization Performance
• Characterization of a half-wave plate for cosmic microwave background circular polarization measurement with POLARBEAR
• A measurement of atmospheric circular polarization with POLARBEAR