Session D8: CMB II

ACTPol: Overview of a next-generation polarization-sensitive CMB observatory in Chile

ACTPol is a new polarization sensitive receiver on the six-meter Atacama Cosmology Telescope which is surveying the Chilean sky and will produce deep maps of the polarization, temperature, and lensing of the Cosmic Microwave Background (CMB) in two frequency bands centered near 90 and 150 GHz. These measurements will improve constraints on inflation, neutrino properties, curvature, the primordial helium abundance, and dark energy. Cross correlating the ACTPol maps with optical surveys accessible from Chile will significantly amplify these constraints. In this talk I provide an overview of the project inclduing discussions of the instrument, science goals, and status of ACTPol.   

ACTPol: Receiver Characterization, Instrument Deployment and Current Status

ACTPol is a new polarization sensitive receiver for the 6\,m Atacama Cosmology Telescope, forming an instrument that will enable a wide range of science goals. The full focal plane will contain $>$3000 transition edge sensors with central frequencies around 90\,GHz and 150\,GHz and operating at 100\,mK. Currently 30\% of this focal plane has been integrated and will be deployed at the site in Chile. In this talk I will discuss the laboratory characterization, deployment, and status of the instrument.   

First CMB Polarization Measurements from SPTpol

The South Pole Telescope (SPT) is a 10-meter mm-wave telescope located at the geographic South Pole, and dedicated to measurements of the cosmic microwave background (CMB). We installed a new, polarization-sensitive receiver (SPTpol) in January 2012, and spent the 2012 Austral winter observing the 100 square degree SPT deep field. SPTpol is among the first of a new generation of CMB experiments capable of detecting the $\sim$100s nK fluctuations of the CMB's B-mode polarization. It has 1536 polarization-sensitive detectors split between 150 GHz and 90 GHz observing bands, and can measure arcminute-scale features on the CMB sky. Here I present early results from the SPTpol E-mode and B-mode CMB polarization measurements.   

Cosmological Results from Sunyaev-Zel'dovich-selected Galaxy Clusters in the 2500-square-degree SPT-SZ Survey

The South Pole Telescope (SPT) is a 10-meter millimeter-wavelength telescope located at the geographic South Pole. In Fall 2011 the SPT completed a three band (90, 150, 220 GHz) survey of 2500 deg$^{2}$ of the southern sky. One of the primary objectives of this survey was the compilation of a nearly mass-limited sample of galaxy clusters selected via the Sunyaev-Zel'dovich (SZ) Effect. The final sample consists of $\sim$550 galaxy clusters ($>85\%$ new discoveries) with a median mass of 3x10$^{14}M_{solar}$/h, a median redshift of 0.55, and a maximum spectroscopic redshift to date of 1.47. I will highlight recent cosmological results derived from the cluster sample and discuss on-going efforts to improve the calibration of the mass-SZ observable relation. With improved mass calibration, the full SPT-SZ cluster sample will constrain the dark energy equation of state parameter, w, with a precision of $\sigma_{w}$ = 0.05 when combined with WMAP and $\sigma_{w}$ = 0.075 with galaxy clusters alone. These projected cluster-only constraints are comparable to the best current constraints from geometric measurements of the Universe, and, by measuring the effect of dark energy on the growth of structure, serve as an independent test of the standard dark energy model.   

CMB Temperature Power Spectrum Measurements and Cosmological Constraints from the 2500 Square Degree SPT-SZ Survey

The South Pole Telescope (SPT) is a 10-meter millimeter-wavelength telescope located at the geographic South Pole. I will present a measurement of the cosmic microwave background (CMB) temperature power spectrum from the recently completed 2500 square degree SPT-SZ survey. This measurement covers the third to ninth acoustic peaks in the CMB power spectrum, spanning the damping tail. The data are well fit by the standard LCDM model, and improve constraints on the model parameters; in particular, the angular sound horizon $\theta_s$ improves by a factor of 2.7. In addition, the datasets show interesting hints of deviations from the LCDM model. Combining the CMB data with low-redshift measurements, the sum of the neutrino masses is constrained to be $0.32\pm0.11$ eV. Using the combined dataset, we find an upper limit on the tensor-to-scalar ratio in primordial power spectrum of $r<0.11$, and constrain the running of the spectral index in the primordial power spectrum to be $-0.046 < dn_s/d\ln k < -0.003 $ at 95\% confidence. We have explored other model extensions including curvature, the primordial helium abundance, and the effective number of neutrino species.   

Probing Reionization and Large-Scale Structure with the 2500 Square Degree SPT-SZ Survey

The South Pole Telescope (SPT) is a 10-meter mm-wavelength telescope located at the South Pole. The SPT recently completed a 2500 square degree survey with arcminute resolution at observing frequencies of 95, 150, and 220 GHz. I will present measurements from the SPT survey of the Cosmic Microwave Background (CMB) power spectrum from angular multipoles between $2000 \textless \ell \textless 9400$. This measurement is sensitive to secondary anisotropies of the CMB, in particular the thermal and kinetic Sunyaev-Zel'dovich (SZ) effects, the cosmic infrared background (CIB), and radio galaxies. I will discuss how we can use the SPT data to constrain the kinetic SZ power and determine how long the epoch of reionization lasted, and together with the Planck optical depth constraint, when it began and ended. I will also present constraints on the sum of the neutrino masses based on the thermal SZ power spectrum and bispectrum. Finally, I will discuss future constraints enabled by the combination of the SPT data with higher frequency measurements from the Herschel-SPIRE instrument. The combined data sets will provide further improvements in the CIB and SZ power spectra constraints, leading to unprecedented constraints on structure formation and the reionization history of the universe.   

Gravitational Lensing of the Microwave Background in the 2500 Square Degree SPT Survey

The South Pole Telescope (SPT) is a 10-meter microwave background telescope located at the geographic South Pole that completed a deep multi-band survey of $\sim$2,500 square degrees of the southern sky in Fall 2011. The high angular resolution and sensitivity enable a reconstruction of the matter potential integrated toward the last scattering surface, effectively weighing the Hubble volume. The inferred lensing potential power spectrum is a sensitive probe of cosmological structure growth and geometry beyond the temperature and polarization power spectra. I will present the results of our analysis using an optimal trispectrum estimator to achieve the highest signal-to-noise measurement of gravitational lensing of the CMB to date. Careful control of astrophysical and instrumental contaminants of the non-Gaussian signature of lensing allow us to place robust constraints on dark energy and the sum of the masses of neutrinos. I will also discuss how the correlation of our lensing maps with galaxy clustering surveys can yield novel astrophysical and cosmological information. The talk will conclude by previewing the potential of joint analyses of our lensing measurements with Planck satellite data, as well as of new data currently being collected by SPTpol.   

Final Results from Three Years of Observations with the BICEP Telescope

The BICEP (Background Imaging of Cosmic Extragalactic Polarization) telescope is the first instrument designed specifically to search for the signature of inflation using the polarization of the Cosmic Microwave Background at degree angular scales. BICEP combines polarization sensitive bolometers, operating at 100 and 150 GHz, with a small aperture cryogenic refracting telescope. It operated for three seasons from 2006 through 2008 at the Amundsen-Scott South Pole Station. Results from the first two seasons, published in Chiang et al. (2010), have so far provided the tightest upper limits on B-mode polarization of the CMB. We report on new results that incorporate the full three year data set to improve this constraint. Besides including more data, the new analysis uses a novel method to deproject the dominant source of systematic contamination in BICEP data. The successful design of BICEP is the basis of BICEP2, which operated at the South Pole from 2010 through 2012, and the Keck Array, which began observations in 2011 and is still operating. These experiments are currently producing extremely deep maps of CMB polarization.