Showing papers on "Atacama Cosmology Telescope published in 2017"

Elucidating $\Lambda$CDM: Impact of Baryon Acoustic Oscillation Measurements on the Hubble Constant Discrepancy

Abstract: We examine the impact of baryon acoustic oscillation (BAO) scale measurements on the discrepancy between the value of the Hubble constant ($H_0$) inferred from the local distance ladder and from Planck cosmic microwave background (CMB) data. While the BAO data alone cannot constrain $H_0$, we show that combining the latest BAO results with WMAP, Atacama Cosmology Telescope (ACT), or South Pole Telescope (SPT) CMB data produces values of $H_0$ that are $2.4-3.1\sigma$ lower than the distance ladder, independent of Planck, and that this downward pull was less apparent in some earlier analyses that used only angle-averaged BAO scale constraints rather than full anisotropic information. At the same time, the combination of BAO and CMB data also disfavors the lower values of $H_0$ preferred by the Planck high-multipole temperature power spectrum. Combining galaxy and Lyman-$\alpha$ forest (Ly$\alpha$) BAO with a precise estimate of the primordial deuterium abundance produces $H_0=66.98\pm1.18$ km s$^{-1}$ Mpc$^{-1}$ for the flat $\Lambda$CDM model. This value is completely independent of CMB anisotropy constraints and is $3.0\sigma$ lower than the latest distance ladder constraint, although $2.4\sigma$ tension also exists between the galaxy BAO and Ly$\alpha$ BAO. These results show that it is not possible to explain the $H_0$ disagreement solely with a systematic error specific to the Planck data. The fact that tensions remain even after the removal of any single data set makes this intriguing puzzle all the more challenging to resolve.

The Atacama Cosmology Telescope: Two-season ACTPol spectra and parameters

Abstract: We present the temperature and polarization angular power spectra measured by the Atacama Cosmology Telescope Polarimeter (ACTPol). We analyze night-time data collected during 2013{14 using two detector arrays at 149 GHz, from 548 deg2 of sky on the celestial equator. We use these spectra, and the spectra measured with the MBAC camera on ACT from 2008{10, in combination with Planck and WMAP data to estimate cosmological parameters from the temperature, polarization, and temperature-polarization cross-correlations. We �nd the new ACTPol data to be consistent with the �CDM model. The ACTPol temperature-polarization cross-spectrum now provides stronger constraints on multiple parameters than the ACTPol temperature spectrum, including the baryon density, the acoustic peak angular scale, and the derived Hubble constant. The new ACTPol data provide information on damping tail parameters. The joint uncertainty on the number of neutrino species and the primordial helium fraction is reduced by 20% when adding ACTPol to Planck temperature data alone.

Two-season Atacama Cosmology Telescope polarimeter lensing power spectrum

Abstract: We report a measurement of the power spectrum of cosmic microwave background (CMB) lensing from two seasons of Atacama Cosmology Telescope polarimeter (ACTPol) CMB data. The CMB lensing power spectrum is extracted from both temperature and polarization data using quadratic estimators. We obtain results that are consistent with the expectation from the best-fit Planck ΛCDM model over a range of multipoles L=80–2100, with an amplitude of lensing Alens=1.06±0.15(stat)±0.06(sys) relative to Planck. Our measurement of the CMB lensing power spectrum gives σ8Ω 0.25 m=0.643±0.054; including baryon acoustic oscillation scale data, we constrain the amplitude of density fluctuations to be σ8=0.831±0.053. We also update constraints on the neutrino mass sum. We verify our lensing measurement with a number of null tests and systematic checks, finding no evidence of significant systematic errors. This measurement relies on a small fraction of the ACTPol data already taken; more precise lensing results can therefore be expected from the full ACTPol data set.

The Atacama Cosmology Telescope: The Two-Season ACTPol Sunyaev-Zel'dovich Effect Selected Cluster Catalog

Abstract: We present a catalog of 182 galaxy clusters detected through the Sunyaev-Zel'dovich effect by the Atacama Cosmology Telescope in a contiguous 987.5 deg$^{2}$ field. The clusters were detected as SZ decrements by applying a matched filter to 148 GHz maps that combine the original ACT equatorial survey with data from the first two observing seasons using the ACTPol receiver. Optical/IR confirmation and redshift measurements come from a combination of large public surveys and our own follow-up observations. Where necessary, we measured photometric redshifts for clusters using a pipeline that achieves accuracy $\Delta z/(1 + z)=0.015$ when tested on SDSS data. Under the assumption that clusters can be described by the so-called Universal Pressure Profile and its associated mass-scaling law, the full signal-to-noise > 4 sample spans the mass range $1.6 4 \times 10^{14}$ M$_{\odot}$ is consistent with the number of such clusters found in the South Pole Telescope SZ survey.

Detection of the pairwise kinematic Sunyaev-Zel'dovich effect with BOSS DR11 and the Atacama Cosmology Telescope

Abstract: We present a new measurement of the kinematic Sunyaev-Zel'dovich effect using data from the Atacama Cosmology Telescope (ACT) and the Baryon Oscillation Spectroscopic Survey (BOSS). Using 600 square degrees of overlapping sky area, we evaluate the mean pairwise baryon momentum associated with the positions of 50,000 bright galaxies in the BOSS DR11 Large Scale Structure catalog. A non-zero signal arises from the large-scale motions of halos containing the sample galaxies. The data fits an analytical signal model well, with the optical depth to microwave photon scattering as a free parameter determining the overall signal amplitude. We estimate the covariance matrix of the mean pairwise momentum as a function of galaxy separation, using microwave sky simulations, jackknife evaluation, and bootstrap estimates. The most conservative simulation-based errors give signal-to-noise estimates between 3.6 and 4.1 for varying galaxy luminosity cuts. We discuss how the other error determinations can lead to higher signal-to-noise values, and consider the impact of several possible systematic errors. Estimates of the optical depth from the average thermal Sunyaev-Zel'dovich signal at the sample galaxy positions are broadly consistent with those obtained from the mean pairwise momentum signal.

Cosmological Parameters From Pre-Planck CMB Measurements: A 2017 Update

Abstract: We present cosmological constraints from the combination of the full mission nine-year WMAP release and small-scale temperature data from the pre-Planck Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT) generation of instruments. This is an update of the analysis presented in Calabrese et al. [Phys. Rev. D 87, 103012 (2013)], and highlights the impact on CDM cosmology of a 0.06 eV massive neutrino which was assumed in the Planck analysis but not in the ACTSPT analyses and a Planck-cleaned measurement of the optical depth to reionization. We show that cosmological constraints are now strong enough that small differences in assumptions about reionization and neutrino mass give systematic differences which are clearly detectable in the data. We recommend that these updated results be used when comparing cosmological constraints from WMAP, ACT and SPT with other surveys or with current and future full-mission Planck cosmology. Cosmological parameter chains are publicly available on the NASAs LAMBDA data archive.

Relieving tensions related to the lensing of the cosmic microwave background temperature power spectra

Abstract: The angular power spectra of the cosmic microwave background (CMB) temperature anisotropies reconstructed from Planck data seem to present “too much” gravitational lensing distortion. This is quantified by the control parameter A L that should be compatible with unity for a standard cosmology. With the class Boltzmann solver and the profile-likelihood method, for this parameter we measure a 2.6 σ shift from 1 using the Planck public likelihoods. We show that, owing to strong correlations with the reionization optical depth τ and the primordial perturbation amplitude A s , a ~ 2 σ tension on τ also appears between the results obtained with the low ( l ≤ 30) and high (30 l ≲ 2500) multipoles likelihoods. With Hillipop, another high- l likelihood built from Planck data, this difference is lowered to 1.3 σ . In this case, the A L value is still in disagreement with unity by 2.2 σ , suggesting a non-trivial effect of the correlations between cosmological and nuisance parameters. To better constrain the nuisance foregrounds parameters, we include the very-high- l measurements of the Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT) experiments and obtain A L = 1.03 ± 0.08. The Hillipop+ACT+SPT likelihood estimate of the optical depth is τ = 0.052 ± 0.035, which is now fully compatible with the low- l likelihood determination. After showing the robustness of our results with various combinations, we investigate the reasons for this improvement that results from a better determination of the whole set of foregrounds parameters. We finally provide estimates of the Λ cold dark matter parameters with our combined CMB data likelihood.

Characterization of the Mid-Frequency Arrays for Advanced ACTPol

Abstract: The Advanced ACTPol upgrade on the Atacama Cosmology Telescope aims to improve the measurement of the cosmic microwave background anisotropies and polarization, using four new dichroic detector arrays fabricated on 150-mm silicon wafers. These bolometric cameras use AlMn transition-edge sensors, coupled to feedhorns with orthomode transducers for polarization sensitivity. The first deployed camera is sensitive to both 150 GHz and 230 GHz. Here we present the lab characterization of the thermal parameters and optical efficiencies for the two newest fielded arrays, each sensitive to both 90 GHz and 150 GHz. We provide assessments of the parameter uniformity across each array with evaluation of systematic uncertainties. Lastly, we show the arrays' initial performance in the field.

Searching for Fossil Evidence of AGN Feedback in WISE-selected Stripe-82 Galaxies by Measuring the Thermal Sunyaev-Zel’dovich Effect with the Atacama Cosmology Telescope

Abstract: We directly measure the thermal energy of the gas surrounding galaxies through the thermal Sunyaev-Zel'dovich (tSZ) effect. We perform a stacking analysis of microwave background images from the Atacama Cosmology Telescope, around 1179 massive quiescent elliptical galaxies at 0.5 <= z <= 1.0 ('low-z') and 3274 galaxies at 1.0 <= z <= 1.5 ('high-z'), selected using data from the Wide-Field Infrared Survey Explorer All-Sky Survey and the Sloan Digital Sky Survey (SDSS) within the SDSS Stripe-82 field. The gas surrounding these galaxies is expected to contain energy from past episodes of active galactic nucleus (AGN) feedback, and after using modeling to subtract undetected contaminants, we detect a tSZ signal at a significance of 0.9-sigma for our low-z galaxies and 1.8-sigma for our high-z galaxies. We then include data from the high-frequency Planck bands for a subset of 227 low-z galaxies and 529 high-z galaxies and find low-z and high-z tSZ detections of 1.0-sigma and 1.5-sigma, respectively. These results indicate an average thermal heating around these galaxies of 5.6(+5.9/-5.6) x 10^60 erg for our low-z galaxies and 7.0(+4.7/-4.4) x 10^60 erg for our high-z galaxies. Based on simple heating models, these results are consistent with gravitational heating without additional heating due to AGN feedback.

Planck intermediate results LII. Planet flux densities

Abstract: Measurements of flux density are described for five planets, Mars, Jupiter, Saturn, Uranus, and Neptune, across the six Planck High Frequency Instrument frequency bands (100‐857 GHz) and these are then compared with models and existing data. In our analysis, we have also included estimates of the brightness of Jupiter and Saturn at the three frequencies of the Planck Low Frequency Instrument (30, 44, and 70 GHz). The results provide constraints on the intrinsic brightness and the brightness time‐variability of these planets. The majority of the planet flux density estimates are limited by systematic errors, but still yield better than 1% measurements in many cases. Applying data from Planck HFI, the Wilkinson Microwave Anisotropy Probe (WMAP), and the Atacama Cosmology Telescope (ACT) to a model that incorporates contributions from Saturn's rings to the planet's total flux density suggests a best fit value for the spectral index of Saturn's ring system of beta(ring) = 2 : 30 +/‐ 0 : 03 over the 30‐1000 GHz frequency range. Estimates of the polarization amplitude of the planets have also been made in the four bands that have polarization‐sensitive detectors (100‐353 GHz); this analysis provides a 95% confidence level upper limit on Mars's polarization of 1.8, 1.7, 1.2, and 1.7% at 100, 143, 217, and 353 GHz, respectively. The average ratio between the Planck‐HFI measurements and the adopted model predictions for all five planets (excluding Jupiter observations for 353 GHz) is 1.004, 1.002, 1.021, and 1.033 for 100, 143, 217, and 353 GHz, respectively. Model predictions for planet thermodynamic temperatures are therefore consistent with the absolute calibration of Planck‐HFI detectors at about the three‐percent level. We compare our measurements with published results from recent cosmic microwave background experiments. In particular, we observe that the flux densities measured by Planck HFI and WMAP agree to within 2%. These results allow experiments operating in the mm‐wavelength range to cross‐calibrate against Planck and improve models of radiative transport used in planetary science.

Testing cosmic acceleration for w(z) parametrizations using fgas measurements in galaxy clusters

Abstract: In this paper we study the cosmic acceleration for five dynamical dark energy models whose equation of state varies with redshift. The cosmological parameters of these models are constrained by performing a MCMC analysis using mainly gas mass fraction, $f_{gas}$, measurements in two samples of galaxy clusters: one reported by Allen et al. (2004), which consists of $42$ points spanning the redshift range $0.05

Advanced ACTPol Low Frequency Array: Readout and Characterization of Prototype 27 and 39 GHz Transition Edge Sensors

Abstract: Advanced ACTPol (AdvACT) is a third generation polarization upgrade to the Atacama Cosmology Telescope, designed to observe the cosmic microwave background (CMB). AdvACT expands on the 90 and 150 GHz transition edge sensor (TES) bolometer arrays of the ACT Polarimeter (ACTPol), adding both high frequency (HF, 150/230 GHz) and low frequency (LF, 27/39 GHz) multichroic arrays. The addition of the high and low frequency detectors allows for the characterization of synchrotron and spinning dust emission at the low frequencies and foreground emission from galactic dust and dusty star forming galaxies at the high frequencies. The increased spectral coverage of AdvACT will enable a wide range of CMB science, such as improving constraints on dark energy, the sum of the neutrino masses, and the existence of primordial gravitational waves. The LF array will be the final AdvACT array, replacing one of the MF arrays for a single season. Prior to the fabrication of the final LF detector array, we designed and characterized prototype TES bolometers. Detector geometries in these prototypes are varied in order to inform and optimize the bolometer designs for the LF array, which requires significantly lower noise levels and saturation powers (as low as ${\sim}1$ pW) than the higher frequency detectors. Here we present results from tests of the first LF prototype TES detectors for AdvACT, including measurements of the saturation power, critical temperature, thermal conductance and time constants. We also describe the modifications to the time-division SQUID readout architecture compared to the MF and HF arrays.

Exploring The Universe With The Atacama Cosmology Telescope: Polarization-Sensitive Measurements Of The Cosmic Microwave Background

Abstract: Over the past twenty-five years, observations of the Cosmic Microwave Background (CMB) temperature fluctuations have served as an important tool for answering some of the most fundamental questions of modern cosmology: how did the universe begin, what is it made of, and how did it evolve? More recently, measurements of the faint polarization signatures of the CMB have offered a complementary means of probing these questions, helping to shed light on the mysteries of cosmic inflation, relic neutrinos, and the nature of dark energy. A second-generation receiver for the Atacama Cosmology Telescope (ACT), the Atacama Cosmology Telescope Polarimeter (ACTPol), was designed and built to take advantage of both these cosmic signals by measuring the CMB to high precision in both temperature and polarization. The receiver features three independent sets of cryogenically cooled optics coupled to transition-edge sensor (TES) based polarimeter arrays via monolithic silicon feedhorn stacks. The three detector arrays, two operating at 149 GHz and one operating at both 97 and 149 GHz, contain over 1000 detectors each and are continuously cooled to a temperature near 100 mK by a custom-designed dilution refrigerator insert. Using ACT's six meter diameter primary mirror and diffraction limited optics, ACTPol is able to make high-fidelity measurements of the CMB at small angular scales (l ~ 9000), providing an excellent complement to Planck. The design and operation of the instrument are discussed in detail, and results from the first two years of observations are presented. The data are broadly consistent with /\CDM and help improve constraints on model extensions when combined with temperature measurements from Planck. Degree Type Dissertation Degree Name Doctor of Philosophy (PhD) Graduate Group Physics & Astronomy First Advisor Mark Devlin Subject Categories Astrophysics and Astronomy This dissertation is available at ScholarlyCommons: https://repository.upenn.edu/edissertations/2990 EXPLORING THE UNIVERSE WITH THE ATACAMA COSMOLOGY TELESCOPE: POLARIZATION-SENSITIVE MEASUREMENTS OF THE COSMIC MICROWAVE BACKGROUND Marius Lungu A DISSERTATION in Physics and Astronomy Presented to the Faculties of the University of Pennsylvania in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy 2017 Supervisor of Dissertation Mark Devlin, Professor of Physics Graduate Group Chairperson Joshua Klein, Professor of Physics Dissertation Committee James Aguirre, Professor of Physics Gary Bernstein, Professor of Physics Bhuvnesh Jain, Professor of Physics Evelyn Thomson, Professor of Physics

Large Millimeter Bolometric Arrays on ACT for Cosmic Microwave Background Observations

Abstract: Two upgraded cameras on the Atacama Cosmology Telescope (ACT), the ACT Polarimeter (ACTPol) and the Advanced ACTPol, have made and will make measurements of the temperature and polarization in the Cosmic Microwave Background (CMB) with arcminute resolution. The ACT observing site is located 5200 m near the top of Cerro Toco in the Atacama Desert of northern Chile. This thesis work is based on my efforts on ACTPol and Advanced ACTPol since 2013 and presents research with the polarimeters employed to map the CMB sky with the ACT’s focal plane arrays at multiple frequency bands. In the Chapter 1, the Cosmic Microwave Background is reviewed and an introduction of current CMB telescopes with a concentration on ground based systems currentlyed in Chile and at the South Pole is presented. Also, an overview of ACT telescope is detailed, on the site, the instrument and the scan strategy. Chapter 2 describes the bolometer physics and properties of the ACTPol’s and the Advanced ACTPol’s detectors. Chapter 3 describes the implementation of the multiplexing readout systems for these two cameras and the readout assembly schematics. Chapter 4 describes the work on the assembly of the detector array, which details all the procedures to put together the array package. It includes the work on the assembly of the ACTPol’s second and third arrays as well as the first three arrays of the Advanced ACTPol. Thus this section compares the similarity and difference between two generations of the cameras; and also presents the challenges moving toward high-density arrays. Chapter ?? summarizes the analysis which characterizes the ACT detector performance in the lab and in-situ. By the time of this dissertation, there have been 6 cameras on the ACT telescope, the analysis covers the characterization of these cameras individually or in ensemble for better systematics understanding. Chapter 6 concludes this thesis work with future prospects.