J. E. Carlstrom

Degree Angular Scale Interferometer First Results: A Measurement of the Cosmic Microwave Background Angular Power Spectrum

We present measurements of anisotropy in the cosmic microwave background (CMB) from the first season of observations with the Degree Angular Scale Interferometer (DASI). The instrument was deployed at the South Pole in the austral summer 1999-2000, and we made observations throughout the following austral winter. We present a measurement of the CMB angular power spectrum in the range 100 < l < 900 in nine bands with fractional uncertainties in the range 10%-20% and dominated by sample variance. In this paper, we review the formalism used in the analysis, in particular the use of constraint matrices to project out contaminants such as ground and point source signals and to test for correlations with diffuse foreground templates. We find no evidence of foregrounds other than point sources in the data, and we find a maximum likelihood temperature spectral index β = -0.1 ± 0.2 (1 σ), consistent with CMB. We detect a first peak in the power spectrum at l ~ 200, in agreement with previous experiments. In addition, we detect a peak in the power spectrum at l ~ 550 and power of similar magnitude at l ~ 800, which are consistent with the second and third harmonic peaks predicted by adiabatic inflationary cosmological models.

DETECTION OF POLARIZATION IN THE COSMIC MICROWAVE BACKGROUND USING DASI

The past several years have seen the emergence of a standard cosmological model, in which small temperature differences in the cosmic microwave background (CMB) radiation on angular scales of the order of a degree are understood to arise from acoustic oscillations in the hot plasma of the early Universe, arising from primordial density fluctuations. Within the context of this model, recent measurements of the temperature fluctuations have led to profound conclusions about the origin, evolution and composition of the Universe. Using the measured temperature fluctuations, the theoretical framework predicts the level of polarization of the CMB with essentially no free parameters. Therefore, a measurement of the polarization is a critical test of the theory and thus of the validity of the cosmological parameters derived from the CMB measurements. Here we report the detection of polarization of the CMB with the Degree Angular Scale Interferometer (DASI). The polarization is deteced with high confidence, and its level and spatial distribution are in excellent agreement with the predictions of the standard theory.

A measurement of the damping tail of the cosmic microwave background power spectrum with the South Pole Telescope

We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) using data from the South Pole Telescope (SPT). The data consist of 790 square degrees of sky observed at 150 GHz during 2008 and 2009. Here we present the power spectrum over the multipole range 650 < ‘ < 3000, where it is dominated by primary CMB anisotropy. We combine this power spectrum with the power spectra from the seven-year Wilkinson Microwave Anisotropy Probe (WMAP) data release to constrain cosmological models. We nd that the SPT and WMAP data are consistent with each other and, when combined, are well t by a spatially at, CDM cosmological model. The SPT+WMAP constraint on the spectral index of scalar uctuations is ns = 0:9663 0:0112. We detect, at 5 signicance, the eect of gravitational lensing on the CMB power spectrum, and nd its amplitude to be consistent with the CDM cosmological model. We explore a number of extensions beyond the CDM model. Each extension is tested independently, although there are degeneracies between some of the extension parameters. We constrain the tensorto-scalar ratio to be r < 0:21 (95% CL) and constrain the running of the scalar spectral index to be dns=d lnk = 0:024 0:013. We strongly detect the eects of primordial helium and neutrinos on the CMB; a model without helium is rejected at 7.7 , while a model without neutrinos is rejected at 7.5 . The primordial helium abundance is measured to be Yp = 0:296 0:030, and the eective number of relativistic species is measured to be Ne = 3:85 0:62. The constraints on these models are strengthened when the CMB data are combined with measurements of the Hubble constant and the baryon acoustic oscillation feature. Notable improvements include ns = 0:9668 0:0093, r < 0:17 (95% CL), and Ne = 3:86 0:42. The SPT+WMAP data show a mild preference for low power in the CMB damping tail, and while this preference may be accommodated by models that have a negative spectral running, a high primordial helium abundance, or a high eective number of relativistic species, such models are disfavored by the abundance of low-redshift galaxy clusters. Subject headings: cosmology { cosmology:cosmic microwave background { cosmology: observations { large-scale structure of universe

The Anisotropy of the microwave background to l = 3500: Mosaic observations with the Cosmic Background Imager

We report measurements of anisotropy in the cosmic microwave background radiation over the multipole range l 200 3500 with the Cosmic Background Imager based on deep observations of three fields. These results confirm the drop in power with increasing l first reported in earlier measurements with this instrument and extend the observations of this decline in power out to l 2000. The decline in power is consistent with the predicted damping of primary anisotropies. At larger multipoles, l 1⁄4 2000 3500, the power is 3.1 greater than standard models for intrinsic microwave background anisotropy in this multipole range and 3.5 greater than zero. This excess power is not consistent with expected levels of residual radio source contamination but, for 8e1, is consistent with predicted levels of a secondary Sunyaev-Zeldovich anisotropy. Further observations are necessary to confirm the level of this excess and, if confirmed, determine its origin. Subject headings: cosmic microwave background — cosmology: observations

Cosmological Parameter Extraction from the First Season of Observations with the Degree Angular Scale Interferometer

The Degree Angular Scale Interferometer (\dasi) has measured the power spectrum of the Cosmic Microwave Background anisotropy over the range of spherical harmonic multipoles 100 0.45 and 0.0<=tau_c<=0.4, we find that the total density of the Universe Omega_tot=1.04+/-0.06, and the spectral index of the initial scalar fluctuations n_s=1.01+0.08-0.06, in accordance with the predictions of inflationary theory. In addition we find that the physical density of baryons Omega_b.h^2=0.022+0.004-0.003, and the physical density of cold dark matter Omega_cdm.h^2=0.14+/-0.04. This value of Omega_b.h^2 is consistent with that derived from measurements of the primordial abundance ratios of the light elements combined with big bang nucleosynthesis theory. Using the result of the HST Key Project h=0.72+/-0.08 we find that Omega_t=1.00+/-0.04, the matter density Omega_m=0.40+/-0.15, and the vacuum energy density Omega_lambda=0.60+/-0.15. (All 68% confidence limits.)The Degree Angular Scale Interferometer (DASI) has measured the power spectrum of the cosmic microwave background anisotropy over the range of spherical harmonic multipoles 100 0.45 and 0.0 ≤ τc ≤ 0.4, we find that the total density of the universe Ωtot = 1.04 ± 0.06 and the spectral index of the initial scalar fluctuations ns = 1.01 in accordance with the predictions of inflationary theory. In addition, we find that the physical density of baryons Ωbh2 = 0.022, and the physical density of cold dark matter Ωcdmh2 = 0.14 ± 0.04. This value of Ωbh2 is consistent with that derived from measurements of the primeval deuterium abundance combined with big bang nucleosynthesis theory. Using the result of the Hubble Space Telescope (HST) Key Project, h = 0.72 ± 0.08, we find that Ωtot = 1.00 ± 0.04, the matter density Ωm = 0.40 ± 0.15, and the vacuum energy density ΩΛ = 0.60 ± 0.15. (All 68% confidence limits.)

Determination of the Cosmic Distance Scale from Sunyaev-Zel'dovich Effect and Chandra X-ray Measurements of High Redshift Galaxy Clusters

We determine the distance to 38 clusters of galaxies in the redshift range 0.14 ≤ z ≤ 0.89 using X-ray data from Chandra and Sunyaev-Zeldovich effect (SZE) data from the Owens Valley Radio Observatory and the Berkeley-Illinois-Maryland Association interferometric arrays. The cluster plasma and dark matter distributions are analyzed using a hydrostatic equilibrium model that accounts for radial variations in density, temperature, and abundance, and the statistical and systematic errors of this method are quantified. The analysis is performed via a Markov chain Monte Carlo technique that provides simultaneous estimation of all model parameters. We measure a Hubble constant of H0 = 76.9 km s-1 Mpc-1 (statistical followed by systematic uncertainty at 68% confidence) for an ΩM = 0.3, ΩΛ = 0.7 cosmology. We also analyze the data using an isothermal β-model that does not invoke the hydrostatic equilibrium assumption and find H0 = 73.7 km s-1 Mpc-1; to avoid effects from cool cores in clusters, we repeated this analysis excluding the central 100 kpc from the X-ray data and find H0 = 77.6 km s-1 Mpc-1 (statistical followed by systematic uncertainty at 68% confidence). The consistency between the models illustrates the relative insensitivity of SZE/X-ray determinations of H0 to the details of the cluster model. Our determination of the Hubble parameter in the distant universe agrees with the recent measurement from the Hubble Space Telescope Key Project that probes the nearby universe.

The relational database and calibration software for the Caltech millimeter array

A relational database management system has been implemented on the Caltech millimeter-wave array for both real-time astronomical engineering data and post-processing calibration and analysis. This system provides high storage-efficiency for the data and on-line access to data from multiple observing seasons. The ability to access easily the full database enables more accurate calibration of the raw data and greatly facilitates the calibration process. In this article we describe both the structure of the mm-array database and the implementation of a data analysis program, both of which make extensive use of Sybase, a commercial database management system with application development software. This use of relational database technology in real-time astronomical data storage and calibration may serve as a prototype for similar systems at other observatories.

Constraints on cosmology from the cosmic microwave background power spectrum of the 2500 deg2 SPT-SZ survey

We explore extensions to the ΛCDM cosmology using measurements of the cosmic microwave background (CMB) from the recent SPT-SZ survey, along with data from WMAP7 and measurements of H_0 and baryon acoustic oscillation (BAO). We check for consistency within ΛCDM between these data sets, and find some tension. The CMB alone gives weak support to physics beyond ΛCDM, due to a slight trend relative to ΛCDM of decreasing power toward smaller angular scales. While it may be due to statistical fluctuation, this trend could also be explained by several extensions. We consider running of the primordial spectral index (dn_s /d ln k), as well as two extensions that modify the damping tail power (the primordial helium abundance Y_p and the effective number of neutrino species N_(eff)) and one that modifies the large-scale power due to the integrated Sachs-Wolfe effect (the sum of neutrino masses ∑m_ν). These extensions have similar observational consequences and are partially degenerate when considered simultaneously. Of the six one-parameter extensions considered, we find CMB to have the largest preference for dn_s/d ln k with –0.046 0 from CMB+BAO+H_0 + SPT_(CL). The median value is (0.32 ± 0.11) eV, a factor of six above the lower bound set by neutrino oscillation observations. All data sets except H_0 show some preference for massive neutrinos; data combinations including H_0 favor nonzero masses only if BAO data are also included. We also constrain the two-parameter extensions N_(eff) + ∑m_ν and N_(eff) + Y_p to explore constraints on additional light species and big bang nucleosynthesis, respectively.

Determining the Cosmic Distance Scale from Interferometric Measurements of the Sunyaev-Zeldovich Effect

We determine the distances to 18 galaxy clusters with redshifts ranging from z ~ 0.14 to 0.78 from a maximum likelihood joint analysis of 30 GHz interferometric Sunyaev-Zeldovich effect (SZE) and X-ray observations. We model the intracluster medium (ICM) using a spherical isothermal β model. We quantify the statistical and systematic uncertainties inherent to these direct distance measurements, and we determine constraints on the Hubble parameter for three different cosmologies. These distances imply a Hubble constant of 60 km s-1 Mpc-1 for an ΩM = 0.3, ΩΛ = 0.7 cosmology, where the uncertainties correspond to statistical followed by systematic at 68% confidence. With a sample of 18 clusters, systematic uncertainties clearly dominate. The systematics are observationally approachable and will be addressed in the coming years through the current generation of X-ray satellites (Chandra and XMM-Newton) and radio observatories (Owens Valley Radio Observatory, Berkeley-Illinois-Maryland Association, and Very Large Array). Analysis of high-redshift clusters detected in future SZE and X-ray surveys will allow a determination of the geometry of the universe from SZE-determined distances.

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.