60 research outputs found
Data analysis methods for the cosmic microwave background
41 pages, 21 figuresInternational audienceIn this review, we give an overview of some of the major aspects of data reduction and analysis for the cosmic microwave background (CMB). Since its prediction and discovery in the last century, the CMB radiation has proven itself to be one of our most valuable tools for precision cosmology. Recently, and especially when combined with complementary cosmological data, measurements of the CMB anisotropies have provided us with a wealth of quantitive information about the birth, evolution and structure of our Universe. We begin with a simple, general introduction to the physics of the CMB, including a basic overview of the experiments which record CMB data. The focus, however, will be the data analysis treatment of CMB data sets
EBEX: A balloon-borne CMB polarization experiment
EBEX is a NASA-funded balloon-borne experiment designed to measure the
polarization of the cosmic microwave background (CMB). Observations will be
made using 1432 transition edge sensor (TES) bolometric detectors read out with
frequency multiplexed SQuIDs. EBEX will observe in three frequency bands
centered at 150, 250, and 410 GHz, with 768, 384, and 280 detectors in each
band, respectively. This broad frequency coverage is designed to provide
valuable information about polarized foreground signals from dust. The
polarized sky signals will be modulated with an achromatic half wave plate
(AHWP) rotating on a superconducting magnetic bearing (SMB) and analyzed with a
fixed wire grid polarizer. EBEX will observe a patch covering ~1% of the sky
with 8' resolution, allowing for observation of the angular power spectrum from
\ell = 20 to 1000. This will allow EBEX to search for both the primordial
B-mode signal predicted by inflation and the anticipated lensing B-mode signal.
Calculations to predict EBEX constraints on r using expected noise levels show
that, for a likelihood centered around zero and with negligible foregrounds,
99% of the area falls below r = 0.035. This value increases by a factor of 1.6
after a process of foreground subtraction. This estimate does not include
systematic uncertainties. An engineering flight was launched in June, 2009,
from Ft. Sumner, NM, and the long duration science flight in Antarctica is
planned for 2011. These proceedings describe the EBEX instrument and the North
American engineering flight.Comment: 12 pages, 9 figures, Conference proceedings for SPIE Millimeter,
Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy V
(2010
Observing the Evolution of the Universe
How did the universe evolve? The fine angular scale (l>1000) temperature and
polarization anisotropies in the CMB are a Rosetta stone for understanding the
evolution of the universe. Through detailed measurements one may address
everything from the physics of the birth of the universe to the history of star
formation and the process by which galaxies formed. One may in addition track
the evolution of the dark energy and discover the net neutrino mass.
We are at the dawn of a new era in which hundreds of square degrees of sky
can be mapped with arcminute resolution and sensitivities measured in
microKelvin. Acquiring these data requires the use of special purpose
telescopes such as the Atacama Cosmology Telescope (ACT), located in Chile, and
the South Pole Telescope (SPT). These new telescopes are outfitted with a new
generation of custom mm-wave kilo-pixel arrays. Additional instruments are in
the planning stages.Comment: Science White Paper submitted to the US Astro2010 Decadal Survey.
Full list of 177 author available at http://cmbpol.uchicago.ed
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
CMB-S4---the next-generation ground-based cosmic microwave background (CMB)
experiment---is set to significantly advance the sensitivity of CMB
measurements and enhance our understanding of the origin and evolution of the
Universe, from the highest energies at the dawn of time through the growth of
structure to the present day. Among the science cases pursued with CMB-S4, the
quest for detecting primordial gravitational waves is a central driver of the
experimental design. This work details the development of a forecasting
framework that includes a power-spectrum-based semi-analytic projection tool,
targeted explicitly towards optimizing constraints on the tensor-to-scalar
ratio, , in the presence of Galactic foregrounds and gravitational lensing
of the CMB. This framework is unique in its direct use of information from the
achieved performance of current Stage 2--3 CMB experiments to robustly forecast
the science reach of upcoming CMB-polarization endeavors. The methodology
allows for rapid iteration over experimental configurations and offers a
flexible way to optimize the design of future experiments given a desired
scientific goal. To form a closed-loop process, we couple this semi-analytic
tool with map-based validation studies, which allow for the injection of
additional complexity and verification of our forecasts with several
independent analysis methods. We document multiple rounds of forecasts for
CMB-S4 using this process and the resulting establishment of the current
reference design of the primordial gravitational-wave component of the Stage-4
experiment, optimized to achieve our science goals of detecting primordial
gravitational waves for at greater than , or, in the
absence of a detection, of reaching an upper limit of at CL.Comment: 24 pages, 8 figures, 9 tables, submitted to ApJ. arXiv admin note:
text overlap with arXiv:1907.0447
CMB-S4
We describe the stage 4 cosmic microwave background ground-based experiment CMB-S4
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
Abstract: CMB-S4âthe next-generation ground-based cosmic microwave background (CMB) experimentâis set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the universe. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semianalytic projection tool, targeted explicitly toward optimizing constraints on the tensor-to-scalar ratio, r, in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2â3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments, given a desired scientific goal. To form a closed-loop process, we couple this semianalytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for r > 0.003 at greater than 5Ï, or in the absence of a detection, of reaching an upper limit of r < 0.001 at 95% CL
De Archeops Ă Planck, analyse des anisotropies du fond diffus cosmologique
LPSC 0588The analysis of cosmic microwave background anisotropies in both temperature and polarisation allows one to constrain the cosmological parameters that describe the Big-Bang model and the early Universe. This thesis is focused on the measurements obtained with the Archeops balloon borne experiment as well as on the future space mission Planck for which Archeops is a test-bench.After a general description of the standard cosmological model and of the CMB physics, this thesis deals more precisely with the reheating mechanism that produces matter at the end of inflation.The next part presents the Archeops and Planck experiments and their data analysis. I have developed various methods designed to study parasitic signals by cosmic rays, to evaluate the bolometer time response and to take into account the asymmetry of the optical beam.The CMB fluctuations analysis is performed by estimating the power spectra in both temperature and polarisation. For this purpose, I present a method that provides a fast unbiased estimation of the power spectra as well as analytic error bars not relying on Monte Carlo simulations. This method has been used to obtain the latest estimate of the Archeops CMB temperature power spectrum.Finally, the last part deals with the implications of the Archeops results for WMAP and Planck. A joint Archeops-WMAP analysis shows the consistency of the CMB measurements through a large frequency range and allows for the detection of the Sunyaev-Zel'dovich effect. In addition, the extrapolation of the Galactic dust polarised power spectra is used as a reference for Planck.L'analyse des anisotropies du fond diffus cosmologique (CMB) en température et en polarisation permet de contraindre une grande partie des paramÚtres cosmologiques décrivant le modÚle du Big-Bang et l'Univers primordial. Cette thÚse s'articule autour des mesures de l'expérience embarquée en ballon Archeops et de la future mission satellite Planck dont Archeops est le prototype. AprÚs une description générale du modÚle standard en cosmologie et de la physique du CMB, cette thÚse aborde plus particuliÚrement le mécanisme de "reheating" qui, à la fin de l'inflation, permet le réchauffement de l'Univers et la formation de la matiÚre. La suite de ce travail présente les expériences Archeops et Planck et l'analyse de leurs données. Dans ce cadre, j'ai développé plusieurs méthodes permettant l'étude des signaux des rayons cosmiques, la mesure des temps de réponse des bolomÚtres ainsi que la prise en compte de l'asymétrie des lobes optiques. L'étude des anisotropies passe par l'estimation des spectres de puissance en température et polarisation. Je présente une méthode rapide et non-biaisée donnant également une estimation analytique précise des barres d'erreur sans avoir recours aux simulations Monte-Carlo. Cette méthode a fourni la derniÚre estimation du spectre de puissance d'Archeops. Enfin, la derniÚre partie traite de l'implication des résultats d'Archeops pour WMAP et Planck. Une analyse jointe Archeops-WMAP montre la cohérence des mesures CMB sur une large gamme de fréquences et la détection de l'effet Sunyaev-Zel'dovich. Par ailleurs, l'extrapolation des spectres polarisés des avant-plans galactiques mesurés par Archeops sert de référence pour Planck
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