100 research outputs found

    Agnostic cosmology in the CAMEL framework

    Full text link
    Cosmological parameter estimation is traditionally performed in the Bayesian context. By adopting an "agnostic" statistical point of view, we show the interest of confronting the Bayesian results to a frequentist approach based on profile-likelihoods. To this purpose, we have developed the Cosmological Analysis with a Minuit Exploration of the Likelihood ("CAMEL") software. Written from scratch in pure C++, emphasis was put in building a clean and carefully-designed project where new data and/or cosmological computations can be easily included. CAMEL incorporates the latest cosmological likelihoods and gives access from the very same input file to several estimation methods: (i) A high quality Maximum Likelihood Estimate (a.k.a "best fit") using MINUIT ; (ii) profile likelihoods, (iii) a new implementation of an Adaptive Metropolis MCMC algorithm that relieves the burden of reconstructing the proposal distribution. We present here those various statistical techniques and roll out a full use-case that can then used as a tutorial. We revisit the Λ\LambdaCDM parameters determination with the latest Planck data and give results with both methodologies. Furthermore, by comparing the Bayesian and frequentist approaches, we discuss a "likelihood volume effect" that affects the optical reionization depth when analyzing the high multipoles part of the Planck data. The software, used in several Planck data analyzes, is available from http://camel.in2p3.fr. Using it does not require advanced C++ skills.Comment: Typeset in Authorea. Online version available at: https://www.authorea.com/users/90225/articles/104431/_show_articl

    Relieving tensions related to the lensing of CMB temperature power spectra

    Full text link
    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 ALA_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 2.6σ\sigma shift from 1 using the Planck public likelihoods. We show that, owing to strong correlations with the reionization optical depth τ\tau and the primordial perturbation amplitude AsA_s, a 2σ\sim2\sigma tension on τ\tau also appears between the results obtained with the low (30\ell\leq 30) and high (30<250030<\ell\lesssim 2500) multipoles likelihoods. With Hillipop, another high-\ell likelihood built from Planck data, this difference is lowered to 1.3σ1.3\sigma. In this case, the ALA_L value is still in disagreement with unity by 2.2σ2.2\sigma, 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 \ell measurements of the Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT) experiments and obtain AL=1.03±0.08A_L = 1.03 \pm 0.08. The Hillipop+ACT+SPT likelihood estimate of the optical depth is τ=0.052±0.035,\tau=0.052\pm{0.035,} which is now fully compatible with the low \ell 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\LambdaCDM parameters with our combined CMB data likelihood.Comment: accepted by A&

    Operations of and Future Plans for the Pierre Auger Observatory

    Full text link
    Technical reports on operations and features of the Pierre Auger Observatory, including ongoing and planned enhancements and the status of the future northern hemisphere portion of the Observatory. Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009.Comment: Contributions to the 31st ICRC, Lodz, Poland, July 200

    The Pierre Auger Observatory III: Other Astrophysical Observations

    Full text link
    Astrophysical observations of ultra-high-energy cosmic rays with the Pierre Auger ObservatoryComment: Contributions to the 32nd International Cosmic Ray Conference, Beijing, China, August 201

    Antennas for the detection of radio emission pulses from cosmic-ray induced air showers at the Pierre Auger Observatory

    Get PDF
    The Pierre Auger Observatory is exploring the potential of the radio detection technique to study extensive air showers induced by ultra-high energy cosmic rays. The Auger Engineering Radio Array (AERA) addresses both technological and scientific aspects of the radio technique. A first phase of AERA has been operating since September 2010 with detector stations observing radio signals at frequencies between 30 and 80 MHz. In this paper we present comparative studies to identify and optimize the antenna design for the final configuration of AERA consisting of 160 individual radio detector stations. The transient nature of the air shower signal requires a detailed description of the antenna sensor. As the ultra-wideband reception of pulses is not widely discussed in antenna literature, we review the relevant antenna characteristics and enhance theoretical considerations towards the impulse response of antennas including polarization effects and multiple signal reflections. On the basis of the vector effective length we study the transient response characteristics of three candidate antennas in the time domain. Observing the variation of the continuous galactic background intensity we rank the antennas with respect to the noise level added to the galactic signal

    The Pierre Auger Observatory IV: Operation and Monitoring

    Full text link
    Technical reports on operations and monitoring of the Pierre Auger ObservatoryComment: Constributions to 32nd International Cosmic Ray Conference, Beijing, China, August 201

    The Pierre Auger Observatory II: Studies of Cosmic Ray Composition and Hadronic Interaction models

    Full text link
    Studies of the composition of the highest energy cosmic rays with the Pierre Auger Observatory, including examination of hadronic physics effects on the structure of extensive air showers.Comment: Contributions to the 32nd International Cosmic Ray Conference, Beijing, China, August 201

    Studies of Cosmic Ray Composition and Air Shower Structure with the Pierre Auger Observatory

    Full text link
    Studies of the composition of the highest energy cosmic rays with the Pierre Auger Observatory, including examination of hadronic physics effects on the structure of extensive air showers. Submissions to the 31st ICRC, Lodz, Poland (July 2009).Comment: Submissions to the 31st International Cosmic Ray Conference, Lodz, Poland (July 2009

    Arecibo PALFA survey and Einstein@Home: Binary pulsar discovery by volunteer computing

    Get PDF
    We report the discovery of the 20.7ms binary pulsar J1952+2630, made using the distributed computing project Einstein@Home in Pulsar ALFA survey observations with the Arecibo telescope. Follow-up observations with the Arecibo telescope confirm the binary nature of the system. We obtain a circular orbital solution with an orbital period of 9.4hr, a projected orbital radius of 2.8lt-s, and a mass function of f = 0.15 M ⊙ by analysis of spin period measurements. No evidence of orbital eccentricity is apparent; we set a 2σ upper limit e ≲ 1.7 × 10 -3 . The orbital parameters suggest a massive white dwarf companion with a minimum mass of 0.95 M ⊙ , assuming a pulsar mass of 1.4 M ⊙ . Most likely, this pulsar belongs to the rare class of intermediate-mass binary pulsars. Future timing observations will aim to determine the parameters of this system further, measure relativistic effects, and elucidate the nature of the companion star. © 2011. The American Astronomical Society. All rights reserved
    corecore