182 research outputs found
Galaxy cluster cosmology with the Atacama Cosmology Telescope
No full textObservations of the Cosmic Microwave Background (CMB) are crucial components of our understanding of cosmology. Modern high resolution, ground-based CMB survey instruments provide important information about the mass and energy content of our present Universe and the high-energy physics of the Big Bang.
In this work we present several aspects of our work on the Atacama Cosmology Telescope (ACT), a 6m telescope in Northern Chile that observed the CMB in three millimetre wavelength bands from 2007–2010. We begin with a description of the Multi-Channel Electronics readout system, an important component of the data acquisition systems for ACT and several other CMB observatories. The system provides room-temperature electronics and software for controlling and reading out arrays of Transition Edge Sensor bolometers via a cryogenic time-domain multiplexing system.
We next present our measurement of the ACT point spread function, or beam, using observations of Solar System planets. An accurate understanding of the beam and its covariant error is essential for interpretation of astrophysical and cosmological signal in the ACT data. We then use our understanding of the beam and the instrument calibration to measure the brightness temperatures of Uranus and Saturn at millimetre wavelengths. Precise measurements of planetary brightnesses provide convenient calibration sources for other observatories at these wavelengths.
Finally we present a sample of galaxy clusters detected in the ACT maps. We develop a new approach for the analysis of Sunyaev-Zeldovich signal that incorporates a model for the typical cluster pressure to better understand selection effects and evaluate cluster masses. Addressing the current level of systematic uncertainty in the overall mass calibration of clusters, we explore the cosmological constraints obtained when calibrating the mass relation based on pressure profile measurements from X-ray data and from models that take different approaches to the cluster physics. Ultimately we use dynamical mass estimates based on optical velocity dispersion measurements to obtain constraints on the amplitude of scalar fluctuations, the matter density, the Dark Energy equation of state parameter, and the sum of the neutrino mass species.Science, Faculty ofPhysics and Astronomy, Department ofGraduat
Localization of a particle due to dissipation in 1 and 2 dimensional lattices
No full textWe study two aspects of the problem of a particle moving on a lattice while subject to dissipation, often called the "Schmid model." First, a correspondence between the Schmid model and boundary sine-Gordon field theory is explored, and a new method is applied to the calculation of the partition function for the theory. Second, a traditional condensed matter formulation of the problem in one spatial dimension is extended to the case of an arbitrary two-dimensional Bravais lattice. A well-known mathematical analogy between one-dimensional dissipative quantum mechanics and string theory provides an equivalence between the Schmid model at the critical point and boundary sine-Gordon theory, which describes a free bosonic field subject to periodic interaction on the boundaries. Using the tools of conformal field theory, the partition function is calculated as a function of the temperature and the renormalized coupling constants of the boundary interaction. The method pursues an established technique of introducing an auxiliary free boson, fermionizing the system, and constructing the boundary state in fermion variables. However, a different way of obtaining the fermionic boundary conditions from the bosonic theory leads to an alternative renormalization for the coupling constants that occurs at a more natural level than in the established approach. Recent renormalization group analyses of the extension of the Schmid model to a two-dimensional periodic potential have yielded interesting new structure in the phase diagram for the mobility. We extend a classic one-dimensional, finite temperature calculation to the case of an arbitrary two-dimensional Bravais lattice. The duality between weak-potential and tightbinding lattice limits is reproduced in the two-dimensional case, and a perturbation expansion in the potential strength used to verify the change in the critical dependence of the mobility on the strength of the dissipation. With a triangular lattice the possibility of third order contributions arises, and we obtain some preliminary expressions for their contributions to the mobility.Science, Faculty ofPhysics and Astronomy, Department ofGraduat
ACTPol: a polarization-sensitive receiver for the Atacama Cosmology Telescope.
No full textThe six-meter Atacama Cosmology Telescope (ACT) in Chile was built to measure the cosmic microwave background (CMB) at arcminute angular scales.
We are building a new polarization sensitive receiver for ACT (ACTPol). ACTPol will characterize the gravitational lensing of the CMB and aims
to constrain the sum of the neutrino masses with ~ 0.05 eV precision, the running of the spectral index of inflation-induced fluctuations, and
the primordial helium abundance to better than 1 %. Our observing fields will overlap with the SDSS BOSS survey at optical wavelengths, enabling
a variety of cross-correlation science, including studies of the growth of cosmic structure from Sunyaev-Zel'dovich observations of clusters of
galaxies as well as independent constraints on the sum of the neutrino masses. We describe the science objectives and the initial receiver design.
Copyright 2010 Society of Photo-Optical Instrumentation Engineers.
One print or electronic copy may be made for personal use only. Systematic reproduction and distribution,
duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Science, Faculty ofPhysics and Astronomy, Department ofReviewedFacult
BICEP2/SPUD: searching for inflation with degree scale polarimetry from the South Pole.
No full textBICEP2/SPUD is the new powerful upgrade of the existing BICEP1 experiment, a bolometric receiver to study thepolarization of the cosmic microwave background
radiation, which has been in operation at the South Pole since January2006. BICEP2 will provide an improvement up to 10 times mapping speed at 150 GHz compared
to BICEP1, using thesame BICEP telescope mount. SPUD, a series of compact, mechanically-cooled receivers deployed on the DASI mountat the Pole, will provide
similar mapping speed in to BICEP2 in three bands, 100, 150, and 220 GHz. The new systemwill use large TES focal plane arrays to provide unprecedented
sensitivity and excellent control of foregroundcontamination.
Copyright 2008 Society of Photo-Optical Instrumentation Engineers.
One print or electronic copy may be made for personal use only. Systematic reproduction and distribution,
duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Science, Faculty ofPhysics and Astronomy, Department ofReviewedFacult
Modeling and characterization of the SPIDER half-wave plate.
No full textSpider is a balloon-borne array of six telescopes that will observe the Cosmic Microwave Background. The 2624
antenna-coupled bolometers in the instrument will make a polarization map of the CMB with approximately one-half
degree resolution at 145 GHz. Polarization modulation is achieved via a cryogenic sapphire half-wave plate (HWP)
skyward of the primary optic. We have measured millimeter-wave transmission spectra of the sapphire at room and
cryogenic temperatures. The spectra are consistent with our physical optics model, and the data gives excellent
measurements of the indices of A-cut sapphire. We have also taken preliminary spectra of the integrated HWP,
optical system, and detectors in the prototype Spider receiver. We calculate the variation in response of the
HWP between observing the CMB and foreground spectra, and estimate that it should not limit the Spider constraints
on inflation.
Copyright 2010 Society of Photo-Optical Instrumentation Engineers.
One print or electronic copy may be made for personal use only. Systematic reproduction and distribution,
duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Science, Faculty ofPhysics and Astronomy, Department ofReviewedFacult
Design and first-light performance of TES bolometer arrays for submillimeter spectroscopy with ZEUS-2
No full textWe have recently commissioned the 2nd generation redshift(z) and Early Universe Spectrometer (ZEUS-2) at the Caltech Submillimeter Observatory. ZEUS-2 is a long-slit grating spectrometer (R~1000) for observations in the submillimeter wavelength regime that is optimized for observations of redshifted far-infrared spectral lines from galaxies in the early universe. Here we report on the design and first light performance of the first TES bolometer array installed in ZEUS-2. This array features 280 pixels each 1.26 mm square and arranged to provide ∼35 pixel spectra at ∼8 spatial positions on the sky. A 1/4-wavelength back short of 100 micron and gold mesh absorber matching the impedance of free space provides near 90% quantum efficiency for the 350 and 450 micron telluric windows. Array readout is done using SQUID multiplexers and the Multichannel Electronics. We will also report on the progress to install two additional arrays tuned to provide similar performance across the remaining telluric windows between 200-850 microns. 2012 SPIE.
Copyright 2012 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Science, Faculty ofPhysics and Astronomy, Department ofReviewedFacult
Modeling and characterization of the SPIDER half-wave plate
No full textSPIE Astronomical Telescopes + Instrumentation, 2010, San Diego, California, United StatesAuthors: Sean A. Bryan, Peter A. R. Ade, Mandana Amiri, Steve Benton, Richard Bihary, James J. Bock, J. Richard Bond, Joseph A. Bonetti, H. Cynthia Chiang, Carlo R. Contaldi, Brendan P. Crill, Daniel O'Dea, Olivier Dore, Marzieh Farhang, Jeffrey P. Filippini, Laura Fissel, Natalie Gandilo, Sunil Golwala, Jon E. Gudmundsson, Matthew Hasselfield, Mark Halpern, Kyle R. Helson, Gene Hilton, Warren Holmes, Viktor V. Hristov, Kent D. Irwin, William C. Jones, Chao Lin Kuo, Carrie J. MacTavish, Peter Mason, Tracy Morford, Thomas E. Montroy, C. Barth Netterfield, Alexandra S. Rahlin, Carl D. Reintsema, Daniel Riley, John E. Ruhl, Marcus C. Runyan, Matthew A. Schenker, Jamil Shariff, Juan Diego Soler, Amy Transrud, Rebecca Tucker, Carole Tucker, Anthony TurnerSpider is a balloon-borne array of six telescopes that will observe the Cosmic Microwave Background. The 2624 antenna-coupled bolometers in the instrument will make a polarization map of the CMB with approximately one-half degree resolution at 145 GHz. Polarization modulation is achieved via a cryogenic sapphire half-wave plate (HWP) skyward of the primary optic. We have measured millimeter-wave transmission spectra of the sapphire at room and cryogenic temperatures. The spectra are consistent with our physical optics model, and the data gives excellent measurements of the indices of A-cut sapphire. We have also taken preliminary spectra of the integrated HWP, optical system, and detectors in the prototype Spider receiver. We calculate the variation in response of the HWP between observing the CMB and foreground spectra, and estimate that it should not limit the Spider constraints on inflation.Spider is funded by NASA grant number NNX07AL64G, and is also supported by a generous gift from the Gordon and Betty Moore Foundation. WCJ acknowledges the support of the Alfred P. Sloan Foundation.https://www.spiedigitallibrary.org/conference-proceedings-of-spie/7741/1/Modeling-and-characterization-of-the-SPIDER-half-wave-plate/10.1117/12.857837.shor
Keck Array: a pulse tube cooled CMB polarimeter.
No full textThe Keck Array is a cosmic microwave background (CMB) polarimeter that will begin observing from the South Pole in late
2010. The initial deployment will consist of three telescopes similar to BICEP2 housed in ultracompact, pulse tube cooled
cryostats. Two more receivers will be added the following year. In these proceedings we report on the design and performance
of the Keck cryostat. We also report some initial results on the performance of antenna-coupled TES detectors operating in
the presence of a pulse tube. We find that the performance of the detectors is not seriously impacted by the replacement of
BICEP2's liquid helium cryostat with a pulse tube cooled cryostat.
Copyright 2010 Society of Photo-Optical Instrumentation Engineers.
One print or electronic copy may be made for personal use only. Systematic reproduction and distribution,
duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Science, Faculty ofPhysics and Astronomy, Department ofReviewedFacult
The Atacama Cosmology Telescope: The Two-season ACTPol Sunyaev–Zel\u27dovich Effect Selected Cluster Catalog
No full textSystems and control software for the Atacama Cosmology Telescope.
No full textThe Atacama Cosmology Telescope (ACT) is designed to measure temperature anisotropies of the cosmic microwave background (CMB) at arcminute resolution. It
is the first CMB experiment to employ a 32×32 close-packed array of free-space-coupled transition-edge superconducting bolometers. We describe the organization
of the telescope systems and software for autonomous, scheduled operations. When paired with real-time data streaming and display, we are able to operate
the telescope at the remote site in the Chilean Altiplano via the Internet from North America. The telescope had a data rate of 70 GB/day in the 2007 season,
and the 2008 upgrade to three arrays will bring this to 210 GB/day.
Copyright 2008 Society of Photo-Optical Instrumentation Engineers.
One print or electronic copy may be made for personal use only. Systematic reproduction and distribution,
duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Science, Faculty ofPhysics and Astronomy, Department ofReviewedFacult
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