Foreground removal requirements for measuring large-scale CMB B-modes in light of BICEP2

The most convincing confirmation that the B-mode polarization signal detected at degree scales by BICEP2 is due to the Cosmic Microwave Background (CMB) would be the measurement of its large-scale counterpart. We assess the requirements for diffuse component separation accuracy over large portions of the sky in order to measure the large-scale B-mode signal corresponding to a tensor to scalar ratio of r=0.1-0.2. We use the method proposed by Bonaldi & Ricciardi (2011) to forecast the performances of different simulated experiments taking into account noise and foreground removal issues. We do not consider instrumental systematics, and we implicitly assume that they are not the dominant source of error. If this is the case, the confirmation of an r=0.1-0.2 signal is achievable by Planck even for conservative assumptions regarding the accuracy of foreground cleaning. Our forecasts suggest that the combination of this experiment with BICEP2 will lead to an improvement of 25-45% in the constraint on r. A next-generation CMB polarization satellite, represented in this work by the COrE experiment, can reduce dramatically (by almost another order of magnitude) the uncertainty on r. In this case, however, the accuracy of foreground removal becomes critical to fully benefit from the increase in sensitivity.Comment: 8 pages, 3 figures, 1 table. Accepted by MNRA

CMB component separation in the pixel domain

We show that the popular ILC approach is unstable in respect to the division of the sample of map pixels to the set of ``homogeneous'' subsamples. For suitable choice of such subsamples we can obtain the restored CMB signal with amplitudes ranged from zero to the amplitudes of the observed signal. We propose approach which allows us to obtain reasonable estimates of $C_\ell$ at $\ell\leq 30$ and similar to WMAP $C_\ell$ for larger $\ell$. With this approach we reduce some anomalies of the WMAP results. In particular, our estimate of the quadrupole is well consistent to theoretical one, the effect of the ``axis of evil'' is suppressed and the symmetry of the north and south galactic hemispheres increases. This results can change estimates of quadrupole polarization and the redshift of reionization of the Universe. We propose also new simple approach which can improve WMAP estimates of high $\ell$ power spectrum.Comment: 7 pages, 5 figure

Cosmological constraints from Sunyaev-Zeldovich cluster counts: an approach to account for missing redshifts

The accumulation of redshifts provides a significant observational bottleneck when using galaxy cluster surveys to constrain cosmological parameters. We propose a simple method to allow the use of samples where there is a fraction of the redshifts that are not known. The simplest assumption is that the missing redshifts are randomly extracted from the catalogue, but the method also allows one to take into account known selection effects in the accumulation of redshifts. We quantify the reduction in statistical precision of cosmological parameter constraints as a function of the fraction of missing redshifts for simulated surveys, and also investigate the impact of making an incorrect assumption for the distribution of missing redshifts.Comment: 6 pages, 5 figures, accepted by Ap

Selective readout and back-action reduction for wideband acoustic gravitational wave detectors

We present the concept of selective readout for broadband resonant mass gravitational wave detectors. This detection scheme is capable of specifically selecting the signal from the contributions of the vibrational modes sensitive to the gravitational waves, and efficiently rejecting the contribution from non gravitationally sensitive modes. Moreover this readout, applied to a dual detector, is capable to give an effective reduction of the back-action noise within the frequency band of interest. The overall effect is a significant enhancement in the predicted sensitivity, evaluated at the standard quantum limit for a dual torus detector. A molybdenum detector, 1 m in diameter and equipped with a wide area selective readout, would reach spectral strain sensitivities 2x10^{-23}/sqrt{Hz} between 2-6 kHz.Comment: 9 pages, 4 figure

Characterization of polarimetric and total intensity behaviour of a complete sample of PACO radio sources in the radio bands

We thank the anonymous referee for useful comments. We acknowledge financial support by the Italian Ministero dell'Istruzione, Universita e Ricerca through the grant Progetti Premiali 2012-iALMA (CUP C52I13000140001). Partial support by ASI/INAF Agreement 2014-024-R.1 for the Planck LFI Activity of Phase E2 and by ASI through the contract I-022-11-0 LSPE is acknowledged. We thank the staff at the ATCA site, Narrabri (NSW), for the valuable support they provided in running the telescope and in data reduction. The ATCA is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. AB acknowledges support from the European Research Council under the EC FP7 grant number 280127. VG thanks Rocco Lico for the useful discussions. VC acknowledges DustPedia, a collaborative focused research project supported by the European Union under the Seventh Framework Programme (2007-2013) call (proposal no. 606824). The participating institutions are: Cardiff University, UK; National Observatory of Athens, Greece; Ghent University, Belgium; Universite Paris Sud, France; National Institute for Astrophysics, Italy, and CEA (Paris), France. LT and LB acknowledge partial financial support from the Spanish Ministry of Economy and Competitiveness (MINECO), under project AYA-2015-65887-P.Galluzzi, V., Massardi, M., Bonaldi, A., Casasola, V., Gregorini, L., Trombetti, T., Burigana, C., Bonato, M., De Zotti, G., Ricci, R., Stevens, J., Ekers, R.D., Bonavera, L., di Serego Alighieri, S., Liuzzo, E., Ĺopez-Caniego, M., Paladino, R., Toffolatti, L., Tucci, M., Callingham, J.R

A reassessment of the evidence of the Integrated Sachs-Wolfe effect through the WMAP-NVSS correlation

We reassess the estimate of the cross-correlation of the spatial distribution of the NRAO VLA Sky Survey (NVSS) radio sources with that of Cosmic Microwave Background (CMB) anisotropies from the Wilkinson Microwave Anisotropy Probe (WMAP). This re-analysis is motivated by the fact that most previous studies adopted a redshift distribution of NVSS sources inconsistent with recent data. We find that the constraints on the bias-weighted redshift distribution, b(z)xN(z), of NVSS sources, set by the observed angular correlation function, w(theta), strongly mitigate the effect of the choice of N(z). If such constraints are met, even highly discrepant redshift distributions yield NVSS-WMAP cross-correlation functions consistent with each other within statistical errors. The models favoured by recent data imply a bias factor, b(z), decreasing with increasing z, rather than constant, as assumed by most previous analyses. As a consequence, the function b(z)xN(z) has more weight at z<1, i.e. in the redshift range yielding the maximum contribution to the ISW in a standard LambdaCDM cosmology. On the whole, the NVSS turns out to be better suited for ISW studies than generally believed, even in the absence of an observational determination of the redshift distribution. The NVSS-WMAP cross-correlation function is found to be fully consistent with the prediction of the standard LambdaCDM cosmology.Comment: 6 pages, 2 figures, submitted to MNRA

Inhomogeneous mechanical losses in micro-oscillators with high reflectivity coating

We characterize the mechanical quality factor of micro-oscillators covered by a highly reflective coating. We test an approach to the reduction of mechanical losses, that consists in limiting the size of the coated area to reduce the strain and the consequent energy loss in this highly dissipative component. Moreover, a mechanical isolation stage is incorporated in the device. The results are discussed on the basis of an analysis of homogeneous and non-homogeneous losses in the device and validated by a set of Finite-Element models. The contributions of thermoelastic dissipation and coating losses are separated and the measured quality factors are found in agreement with the calculated values, while the absence of unmodeled losses confirms that the isolation element integrated in the device efficiently uncouples the dynamics of the mirror from the support system. Also the resonant frequencies evaluated by Finite-Element models are in good agreement with the experimental data, and allow the estimation of the Young modulus of the coating. The models that we have developed and validated are important for the design of oscillating micro-mirrors with high quality factor and, consequently, low thermal noise. Such devices are useful in general for high sensitivity sensors, and in particular for experiments of quantum opto-mechanics

An ultra-low dissipation micro-oscillator for quantum opto-mechanics

Generating non-classical states of light by opto-mechanical coupling depends critically on the mechanical and optical properties of micro-oscillators and on the minimization of thermal noise. We present an oscillating micro-mirror with a mechanical quality factor Q = 2.6x10^6 at cryogenic temperature and a Finesse of 65000, obtained thanks to an innovative approach to the design and the control of mechanical dissipation. Already at 4 K with an input laser power of 2 mW, the radiation-pressure quantum fluctuations become the main noise source, overcoming thermal noise. This feature makes our devices particularly suitable for the production of pondero-motive squeezing.Comment: 21 pages including Supplementary Informatio

An asymptotic plate model for magneto-electro-thermo-elastic sensors and actuators

International audienceWe present an asymptotic two-dimensional plate model for linear magneto-electro-thermo-elastic sensors and actuators, under the hypotheses of anisotropy and homogeneity. Four different boundary conditions pertaining to electromagnetic quantities are considered, leading to four different models: the sensor-actuator model, the actuator-sensor model, the actuator model and the sensor model. We validate the obtained two-dimensional models by proving weak convergence results. Each of the four plate problems turns out to be decoupled into a flexural problem, involving the transversal displacement of the plate, and a certain partially or totally coupled membrane problem

Dynamical two-mode squeezing of thermal fluctuations in a cavity opto-mechanical system

We report the experimental observation of two-mode squeezing in the oscillation quadratures of a thermal micro-oscillator. This effect is obtained by parametric modulation of the optical spring in a cavity opto-mechanical system. In addition to stationary variance measurements, we describe the dynamic behavior in the regime of pulsed parametric excitation, showing enhanced squeezing effect surpassing the stationary 3dB limit. While the present experiment is in the classical regime, our technique can be exploited to produce entangled, macroscopic quantum opto-mechanical modes