Gravitational lensing due to the large-scale distribution of matter in the cosmos distorts the primordial Cosmic Microwave Background (CMB) and thereby induces new, small-scale B -mode polarization. This signal carries detailed information about the distribution of all the gravitating matter between the observer and CMB last scattering surface. We report the first direct evidence for polarization lensing based on purely CMB information, from using the four-point correlations of even-and odd-parity E -and B -mode polarization mapped over ∼ 30 square degrees of the sky measured by the Polarbear experiment. These data were analyzed using a blind analysis framework and checked for spurious systematic contamination using null tests and simulations. Evidence for the signal of polarization lensing and lensing B -modes is found at 4.2σ (stat.+sys.) significance. The amplitude of matter fluctuations is measured with a precision of 27%, and is found to be consistent with the Lambda Cold Dark Matter (ΛCDM) cosmological model. This measurement demonstrates 2 a new technique, capable of mapping all gravitating matter in the Universe, sensitive to the sum of neutrino masses, and essential for cleaning the lensing B -mode signal in searches for primordial gravitational waves.Introduction: As Cosmic Microwave Background (CMB) photons traverse the Universe, their paths are gravitationally deflected by large-scale structures. By measuring the resulting changes in the statistical properties of the CMB anisotropies, maps of this gravitational lensing deflection, which traces large-scale structure, can be reconstructed. Gravitational lensing of the CMB has been detected in the CMB temperature anisotropy in several ways: in the smoothing of the acoustic peaks of the temperature power spectrum [1-3], in cross-correlations with tracers of the large-scale matter distribution [4][5][6][7][8][9][10], and in the four-point correlation function of CMB temperature maps [11][12][13][14].The South Pole Telescope (SPT) collaboration recently reported a detection of lensed polarization using the cross-correlation between maps of CMB polarization and sub-mm maps of galaxies from Herschel/SPIRE [15]. A companion paper to this one has also shown the evidence of the CMB lensing-Cosmic Infrared Background crosscorrelation results using Polarbear data [16], finding good agreement with the SPT measurements. This crosscorrelation is immune to several instrumental systematic effects but the cosmological interpretation of this measurement requires assumptions about the relation of submm galaxies to the underlying mass distribution [17].In this Letter, we present the first direct evidence for gravitational lensing of the polarized CMB using data from the Polarbear experiment. We present power spectra of the lensing deflection field for two four-point estimators using only CMB polarization data, and tests for spurious systematic contamination of these estimators. We combine the two estimators to increase the signal-to-noise of the lensing detection.CMB lens...
We report a measurement of the B-mode polarization power spectrum in the cosmic microwave background (CMB) using the Polarbear experiment in Chile. The faint B-mode polarization signature carries information about the universe's entire history of gravitational structure formation, and the cosmic inflation that may have occurred in the very early universe. Our measurement covers the angular multipole range 500 < < 2100 and is based on observations of an effective sky area of 25 deg 2 with 3. 5 resolution at 150 GHz. On these angular scales, gravitational lensing of the CMB by intervening structure in the universe is expected to be the dominant source of B-mode polarization. Including both systematic and statistical uncertainties, the hypothesis of no B-mode polarization power from gravitational lensing is rejected at 97.2% confidence. The band powers are consistent with the standard cosmological model. Fitting a single lensing amplitude parameter A BB to the measured band powers, A BB = 1.12 ± 0.61(stat) +0.04 −0.12 (sys) ± 0.07(multi), where A BB = 1 is the fiducial wmap-9 ΛCDM value. In this expression, "stat" refers to the statistical uncertainty, "sys" to the systematic uncertainty associated with possible biases from the instrument and astrophysical foregrounds, and "multi" to the calibration uncertainties that have a multiplicative effect on the measured amplitude A BB .
EBEX is a NASA-funded balloon-borne experiment designed to measure the polarization of the cosmic microwave background (CMB). Observations will be made using 1432 transition edge sensor (TES) bolometric detectors read out with frequency multiplexed SQuIDs. EBEX will observe in three frequency bands centered at 150, 250, and 410 GHz, with 768, 384, and 280 detectors in each band, respectively. This broad frequency coverage is designed to provide valuable information about polarized foreground signals from dust. The polarized sky signals will be modulated with an achromatic half wave plate (AHWP) rotating on a superconducting magnetic bearing (SMB) and analyzed with a fixed wire grid polarizer. EBEX will observe a patch covering ∼1% of the sky with 8' resolution, allowing for observation of the angular power spectrum from = 20 to 1000. This will allow EBEX to search for both the primordial B-mode signal predicted by inflation and the anticipated lensing B-mode signal. Calculations to predict EBEX constraints on r using expected noise levels show that, for a likelihood centered around zero and with negligible foregrounds, 99% of the area falls below r = 0.035. This value increases by a factor of 1.6 after a process of foreground subtraction. This estimate does not include systematic uncertainties. An engineering flight was launched in June, 2009, from Ft. Sumner, NM, and the long duration science flight in Antarctica is planned for 2011. These proceedings describe the EBEX instrument and the North American engineering flight.
We present the design and characterization of the polarbear experiment. polarbear will measure the polarization of the cosmic microwave background (CMB) on angular scales ranging from the experiment's 3.5 beam size to several degrees. The experiment utilizes a unique focal plane of 1,274 antenna-coupled, polarization sensitive TES bolometers cooled to 250 milliKelvin. Employing this focal plane along with stringent control over systematic errors, polarbear has the sensitivity to detect the expected small scale B-mode signal due to gravitational lensing and search for the large scale B-mode signal from inflationary gravitational waves.polarbear was assembled for an engineering run in the Inyo Mountains of California in 2010 and was deployed in late 2011 to the Atacama Desert in Chile. An overview of the instrument is presented along with characterization results from observations in Chile.
We reconstruct the gravitational lensing convergence signal from cosmic microwave background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with cosmic infrared background maps from the Herschel satellite. From the cross spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical significance of 4.0σ and indication of the presence of a lensing B-mode signal at a significance of 2.3σ. We demonstrate that our results are not biased by instrumental and astrophysical systematic errors by performing null tests, checks with simulated and real data, and analytical calculations. This measurement of polarization lensing, made via the robust cross-correlation channel, not only reinforces POLARBEAR auto-correlation measurements, but also represents one of the early steps towards establishing CMB polarization lensing as a powerful new probe of cosmology and astrophysics.
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