W. L. Holzapfel

Neutrino physics from the cosmic microwave background and large scale structure

This is a report on the status and prospects of the quantification of neutrino properties through the cosmological neutrino background for the Cosmic Frontier of the Division of Particles and Fields Community Summer Study long-term planning exercise. Experiments planned and underway are prepared to study the cosmological neutrino background in detail via its influence on distance-redshift relations and the growth of structure. The program for the next decade described in this document, including upcoming spectroscopic galaxy surveys eBOSS and DESI and a new Stage-IV CMB polarization experiment CMB-S4, will achieve σ(σmν) = 16 meV and σ(Neff) = 0.020. Such a mass measurement will produce a high significance detection of non-zero σmν, whose lower bound derived from atmospheric and solar neutrino oscillation data is about 58 meV. If neutrinos have a minimal normal mass hierarchy, this measurement will definitively rule out the inverted neutrino mass hierarchy, shedding light on one of the most puzzling aspects of the Standard Model of particle physics — the origin of mass. This precise a measurement of Neff will allow for high sensitivity to any light and dark degrees of freedom produced in the big bang and a precision test of the standard cosmological model prediction that Neff=3.046.

Interferometric Observation of Cosmic Microwave Background Anisotropies

We present a formalism for analyzing interferometric observations of the cosmic microwave background anisotropy and polarization. The formalism is based on the l-space expansion of the angular power spectrum favored in recent years. Explicit discussions of maximum likelihood analysis, power spectrum reconstruction, parameter estimation, imaging, and polarization are given. As an example, several calculations for the Degree Angular Scale Interferometer and Cosmic Background Interferometer experiments are presented.

Measurement of the Cosmic Microwave Background Polarization Lensing Power Spectrum with the POLARBEAR experiment

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 cosmological model. This measurement demonstrates 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.

Limits on the peculiar velocities of two distant clusters using the kinematic Sunyaev-Zeldovich effect

We report millimeter-wavelength observations of the Sunyaev-Zeldovich (S-Z) effect in two distant galaxy clusters. A relativistically correct analysis of the S-Z data is combined with the results of X-ray observations to determine the radial peculiar velocities (vr) of the clusters. We observed Abell 2163 (z = 0.201) in three millimeter-wavelength bands centered at 2.1, 1.4, and 1.1 mm. We report a significant detection of the thermal component of the S-Z effect seen as both a decrement in the brightness of the CMB at 2.1 mm and as an increment at 1.1 mm. Including uncertainties due to the calibration of the instrument, distribution and temperature of the intracluster gas, and astrophysical confusion, a simultaneous fit to the data in all three bands gives vr=+490−880+1370 km s-1 at 68% confidence. We observed Abell 1689 (z = 0.181) in the 2.1 and 1.4 mm bands. Including the same detailed accounting of uncertainty, a simultaneous fit to the data in both bands gives vr=+170−630+815 km s-1. The limits on the peculiar velocities of A2163 and A1689 correspond to deviations from the uniform Hubble flow of 2%-3%.

The Sunyaev-Zeldovich Infrared Experiment: A Millimeter-Wave Receiver for Cluster Cosmology

Measurements of the Sunyaev-Zeldovich (S-Z) effect toward distant clusters of galaxies can be used to determine the Hubble constant and the radial component of cluster peculiar velocities. Determination of the cluster peculiar velocity requires the separation of the two components of the S-Z effect, which are due to the thermal and bulk velocities of the intracluster plasma. The two components can be separated practically only at millimeter wavelengths. Measurements of the S-Z effect at millimeter wavelengths are subject to minimal astrophysical confusion and, therefore, provide an important test of results obtained at longer wavelengths. We describe the instrument used to make the first significant detections of the S-Z effect at millimeter wavelengths. This instrument employs new filter, detector, and readout technologies to produce sensitive measurements of differential sky brightness stable on long timescales. These advances allow drift-scan observations that achieve high sensitivity while minimizing common sources of systematic error.

Anisotropy in the cosmic microwave background at degree angular scales: Python V results

Observations of the microwave sky using the Python telescope in its fifth season of operation at the Amundsen-Scott South Pole Station in Antarctica are presented. The system consists of a 0.75 m off-axis telescope instrumented with a HEMT amplifier-based radiometer having continuum sensitivity from 37 to 45 GHz in two frequency bands. With a 091 × 102 beam, the instrument fully sampled 598 deg2 of sky, including fields measured during the previous four seasons of Python observations. Interpreting the observed fluctuations as anisotropy in the cosmic microwave background, we place constraints on the angular power spectrum of fluctuations in eight multipole bands up to l ~ 260. The observed spectrum is consistent with both the COBE experiment and previous Python results. There is no significant contamination from known foregrounds. The results show a discernible rise in the angular power spectrum from large (l ~ 40) to small (l ~ 200) angular scales. The shape of the observed power spectrum is not a simple linear rise, but has a sharply increasing slope starting at l ~ 150.

Using Sunyaev-Zeldovich Infrared Experiment (SuZIE) Arcminute-Scale Cosmic Microwave Background Anisotropy Data to Probe Open and Flat Λ Cold Dark Matter Cosmogonies

We use arcminute-scale data from the Sunyaev-Zeldovich Infrared Experiment to set limits on anisotropies in cosmic microwave background radiation in open and spatially flat Λ cold dark matter cosmogonies. There are no 2 σ detections for the models tested. The upper limits obtained are consistent with the amplitude of anisotropy detected by the COBE Differential Microwave Radiometer experiment.

DASI: a Degree Angular Scale Interferometer for imaging anisotropy in the cosmic microwave background

The Degree Angular Scale Interferometer (DASI) is a compact cm-wave interferometer designed to image anisotropy in the Cosmic Microwave Background (CMB) and to measure its angular power spectrum. The power spectrum will be densely sampled over the l range 160 to 710, corresponding to angular scales of 0.25 to 1.15 degrees. DASI consists of 13 elements. Each element consists of a 20-cm diameter lensed corrugated horn followed by a cooled low-noise HEMT amplifier operating from 26 - 36 GHz. All elements are mounted on a single alt-az mount, which fixes the projected baselines and obviates an IF tracking delay. The mount also includes rotation of the aperture plane along the line of sight to improve the u, v coverage and the control of instrumental systematics. The 10 GHz IF bandwidth will be correlated in 1 GHz bands to provide spectral index information. The instrument is scheduled to be completed in Summer 1998. After extensive testing it will be deployed at the South Pole for year-round operation starting in November 1999.

Constraints on Cosmological Parameters from the Angular Power Spectrum of a Combined 2500 deg

We report constraints on cosmological parameters from the angular power spectrum of a cosmic microwave background (CMB) gravitational lensing potential map created using temperature data from 2500 deg2 of South Pole Telescope (SPT) data supplemented with data from Planck in the same sky region, with the statistical power in the combined map primarily from the SPT data. We fit the lensing power spectrum to a model including cold dark matter and a cosmological constant (ΛCDM), and to models with single-parameter extensions to ΛCDM. We find constraints that are comparable to and consistent with those found using the full-sky Planck CMB lensing data, e.g., σ_8 Ω^(0.25)_m = 0.598 ± 0.024 from the lensing data alone with weak priors placed on other parameters. Combining with primary CMB data, we explore single-parameter extensions to ΛCDM. We find Ω_k = -0.012^(+0.021)_(-0.023) or M_ν < 0.70 eV at 95% confidence, in good agreement with results including the lensing potential as measured by Planck. We include two parameters that scale the effect of lensing on the CMB: A_L, which scales the lensing power spectrum in both the lens reconstruction power and in the smearing of the acoustic peaks, and A^(oo), which scales only the amplitude of the lensing reconstruction power spectrum. We find A^(oo) x A_L = 1.01 ± 0.08 for the lensing map made from combined SPT and Planck data, indicating that the amount of lensing is in excellent agreement with expectations from the observed CMB angular power spectrum when not including the information from smearing of the acoustic peaks.

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We review recent results of Sunyaev-Zel’dovich-effect (SZE) observations toward galaxy clusters. Using cm-wave receivers mounted on the OVRO and BIMA mm-wave arrays, we have obtained high signal-to-noise images of the effect for more than 25 clusters. Over 90% of these clusters are scheduled to be observed with AXAF during the first year of its observations. We present current estimates of cosmological parameters H0 and Ωm based on the SZE in galaxy clusters.