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  • Journal article
    Renzini AI, Contaldi CR, 2019,

    Gravitational wave background sky maps from advanced LIGO O1 data

    , PHYSICAL REVIEW LETTERS

    We integrate the publicly available O1 LIGO time-domain data to obtain maximum-likelihood constraints on the Gravitational Wave Background (GWB) arising from stochastic, persistent signals. Our method produces sky-maps of the strain intensity I as a function of direction on the sky at a reference frequency f0. The data is integrated assuming a set of fixed power-law spectra for the signal. The maps provide upper limits on the amplitude of the GWB density ΩGW(f0) and any anisotropy around the background. We find 95\% confidence upper limits of ΩGW<4.8×10−7 at f0=50 Hz with similar constraints on a dipole modulation for the inspiral-dominated stochastic background case.

  • Journal article
    Bergman AS, Ade PAR, Akers S, Amiri M, Austermann JA, Beall JA, Becker DT, Benton SJ, Bock JJ, Bond JR, Bryan SA, Chiang HC, Contaldi CR, Domagalski RS, Dore O, Duff SM, Duivenvoorden AJ, Eriksen HK, Farhang M, Filippini JP, Fissel LM, Fraisse AA, Freese K, Galloway M, Gambrel AE, Gandilo NN, Ganga K, Grigorian A, Gualtieri R, Gudmundsson JE, Halpern M, Hartley J, Hasselfield M, Hilton G, Holmes W, Hristov VV, Huang Z, Hubmayr J, Irwin KD, Jones WC, Khan A, Kuo CL, Kermish ZD, Li S, Mason PV, Megerian K, Moncelsi L, Morford TA, Nagy JM, Netterfield CB, Nolta M, Osherson B, Padilla IL, Racine B, Rahlin AS, Redmond S, Reintsema C, Romualdez LJ, Ruhl JE, Runyan MC, Ruud TM, Shariff JA, Shaw EC, Shiu C, Soler JD, Song X, Trangsrud A, Tucker C, Tucker RS, Turner AD, Ullom J, van der List JF, Van Lanen J, Vissers MR, Weber AC, Wehus IK, Wen S, Wiebe DV, Young EYet al., 2018,

    280 GHz Focal Plane Unit Design and Characterization for the SPIDER-2 Suborbital Polarimeter

    , JOURNAL OF LOW TEMPERATURE PHYSICS, Vol: 193, Pages: 1075-1084, ISSN: 0022-2291
  • Journal article
    Renzini AI, Contaldi CR, 2018,

    Mapping incoherent gravitational wave backgrounds

    , Monthly Notices of the Royal Astronomical Society, Vol: 481, Pages: 4650-4661, ISSN: 0035-8711

    Given the recent detection of gravitational waves from individual sources, it is almost a certainty that some form of background of gravitational waves will be detected in future. The most promising candidate for such a detection is backgrounds made up of incoherent superposition of the signal of unresolved astrophysical, or backgrounds sourced by earlier cosmological events. Such backgrounds will also contain anisotropies about an average value. The information contained in the background level and any anisotropies will be extremely valuable as an astrophysical and cosmological probe. As such, the ability to reconstruct sky maps of the signal will become important as the sensitivity increases. We build and test a pixel-based, maximum-likelihood gravitational wave background (GWB) map-maker that uses the cross-correlation of sets of generalized baselines as input. The resulting maps are a representation of the GWB power, or strain ‘intensity’ on the sky. We test the algorithm by reconstructing known input maps with different baseline configurations. We also apply the map-maker to a subset of the Advanced Laser Interferometer Gravitational Wave observatory data.

  • Journal article
    Gualtieri R, Filippini JP, Ade PAR, Amiri M, Benton SJ, Bergman AS, Bihary R, Bock JJ, Bond JR, Bryan SA, Chiang HC, Contaldi CR, Doré O, Duivenvoorden AJ, Eriksen HK, Farhang M, Fissel LM, Fraisse AA, Freese K, Galloway M, Gambrel AE, Gandilo NN, Ganga K, Gramillano RV, Gudmundsson JE, Halpern M, Hartley J, Hasselfield M, Hilton G, Holmes W, Hristov VV, Huang Z, Irwin KD, Jones WC, Kuo CL, Kermish ZD, Li S, Mason PV, Megerian K, Moncelsi L, Morford TA, Nagy JM, Netterfield CB, Nolta M, Osherson B, Padilla IL, Racine B, Rahlin AS, Reintsema C, Ruhl JE, Runyan MC, Ruud TM, Shariff JA, Soler JD, Song X, Trangsrud A, Tucker C, Tucker RS, Turner AD, List JFVD, Weber AC, Wehus IK, Wiebe DV, Young EYet al.,

    SPIDER: CMB polarimetry from the edge of space

    , Journal of Low Temperature Physics, ISSN: 0022-2291

    SPIDER is a balloon-borne instrument designed to map the polarization of themillimeter-wave sky at large angular scales. SPIDER targets the B-modesignature of primordial gravitational waves in the cosmic microwave background(CMB), with a focus on mapping a large sky area with high fidelity at multiplefrequencies. SPIDER's first longduration balloon (LDB) flight in January 2015deployed a total of 2400 antenna-coupled Transition Edge Sensors (TESs) at 90GHz and 150 GHz. In this work we review the design and in-flight performance ofthe SPIDER instrument, with a particular focus on the measured performance ofthe detectors and instrument in a space-like loading and radiation environment.SPIDER's second flight in December 2018 will incorporate payload upgrades andnew receivers to map the sky at 285 GHz, providing valuable information forcleaning polarized dust emission from CMB maps.

  • Journal article
    Contaldi CR, Magueijo J, 2018,

    Unsqueezing of standing waves due to inflationary domain structure

    , Physical Review D, Vol: 98, ISSN: 2470-0010

    The so-called trans-Planckian problem of inflation may be evaded by positing that modes come into existence only when they became “cis-Planckian” by virtue of expansion. However, this would imply that for any mode a new random realization would have to be drawn every N wavelengths, with N typically of order 1000 (but it could be larger or smaller). Such a redrawing of realizations leads to a heteroskodastic distribution if the region under observation contains several such independent domains. This has no effect on the sampled power spectrum for a scale-invariant raw spectrum, but at very small scales, it leads to a spectral index bias toward scale invariance and smooths oscillations in the spectrum. The domain structure would also “unsqueeze” some of the propagating waves, i.e., dismantle their standing wave character. By describing standing waves as traveling waves of the same amplitude moving in opposite directions, we determine the observational effects of unsqueezing. We find that it would erase the Doppler peaks in the cosmic microwave background, but only on very small angular scales, in which the primordial signal may not be readily accessible. The standing waves in a primordial gravitational wave background would also be turned into traveling waves. This unsqueezing of the gravitational wave background may constitute a detectable phenomenon.

  • Journal article
    Nagy JM, Ade PAR, Amiri M, Benton SJ, Bergman AS, Bihary R, Bock JJ, Bond JR, Bryan SA, Chiang HC, Contaldi CR, Dore O, Duivenvoorden AJ, Eriksen HK, Farhang M, Filippini JP, Fissel LM, Fraisse AA, Freese K, Galloway M, Gambrel AE, Gandilo NN, Ganga K, Gudmundsson JE, Halpern M, Hartley J, Hasselfield M, Hilton G, Holmes W, Hristov VV, Huang Z, Irwin KD, Jones WC, Kuo CL, Kermish ZD, Li S, Mason PV, Megerian K, Moncelsi L, Morford TA, Netterfield CB, Nolta M, Padilla IL, Racine B, Rahlin AS, Reintsema C, Ruhl JE, Runyan MC, Ruud TM, Shariff JA, Soler JD, Song X, Trangsrud A, Tucker C, Tucker RS, Turner AD, Van Der List JF, Weber AC, Wehus IK, Wiebe DV, Young EYet al., 2017,

    A New Limit on CMB Circular Polarization from SPIDER

    , Astrophysical Journal, Vol: 844, ISSN: 0004-637X

    We present a new upper limit on cosmic microwave background (CMB) circular polarization from the 2015 flight of Spider, a balloon-borne telescope designed to search for B-mode linear polarization from cosmic inflation. Although the level of circular polarization in the CMB is predicted to be very small, experimental limits provide a valuable test of the underlying models. By exploiting the nonzero circular-to-linear polarization coupling of the half-wave plate polarization modulators, data from Spider's 2015 Antarctic flight provide a constraint on Stokes V at 95 and 150 GHz in the range $33\lt {\ell }\lt 307$. No other limits exist over this full range of angular scales, and Spider improves on the previous limit by several orders of magnitude, providing 95% C.L. constraints on ${\ell }({\ell }+1){C}_{{\ell }}^{{VV}}/(2\pi )$ ranging from 141 to 255 μK2 at 150 GHz for a thermal CMB spectrum. As linear CMB polarization experiments become increasingly sensitive, the techniques described in this paper can be applied to obtain even stronger constraints on circular polarization.

  • Journal article
    Renzini AI, Contaldi CR, Heavens A, 2017,

    Mapping weak lensing distortions in the Kerr metric

    , Physical Review D, Vol: 95, ISSN: 2470-0010

    Einstein’s theory of General Relativity implies that energy, i.e., matter, curves space-time and thusdeforms lightlike geodesics, giving rise to gravitational lensing. This phenomenon is well understood in thecase of the Schwarzschild metric and has been accurately described in the past; however, lensing in the Kerrspace-time has received less attention in the literature despite potential practical observational applications.In particular, lensing in such space is not expressible as the gradient of a scalar potential and as such is asource of curl-like signatures and an asymmetric shear pattern. In this paper, we develop a differentiablelensing map in the Kerr metric, reworking and extending previous approaches. By using standard tools ofweak gravitational lensing, we isolate and quantify the distortion that is uniquely induced by the presenceof angular momentum in the metric. We apply this framework to the distortion induced by a Kerr-likeforeground object on a distribution of background of sources. We verify that the new unique lensingsignature is orders of magnitude below current observational bounds for a range of lens configurations.

  • Journal article
    Contaldi CR, 2017,

    Anisotropies of gravitational wave backgrounds: a line of sight approach

    , Physics Letters B, Vol: 771, Pages: 9-12, ISSN: 0370-2693

    In the weak field regime, gravitational waves can be considered as being made up of collisionless, relativistic tensor modes that travel along null geodesics of the perturbed background metric. We work in this geometric optics picture to calculate the anisotropies in gravitational wave backgrounds resulting from astrophysical and cosmological sources. Our formalism yields expressions for the angular power spectrum of the anisotropies. We show how the anisotropies are sourced by intrinsic, Doppler, Sachs–Wolfe, and Integrated Sachs–Wolfe terms in analogy with Cosmic Microwave Background photons.

  • Journal article
    Contaldi CR, 2017,

    Imaging parity-violating modes in the CMB

    , Astronomical Journal, Vol: 153, ISSN: 0004-6256

    Correlations of polarization components in the coordinate frame are a natural basis for searches of parity-violating modes in the cosmic microwave background. This fact can be exploited to build estimators of parity-violating modes that are local and robust with respect to partial-sky coverage or inhomogeneous weighting. As an example application of a method based on these ideas, we develop a peak stacking tool that isolates the signature of parity-violating modes. We apply the tool to Planck maps and obtain a constraint on the monopole of the polarization rotation angle $\alpha \lt 0\buildrel{\circ}\over{.} 72$ at 95% We also demonstrate how the tool can be used as a local method for reconstructing maps of direction dependent rotation $\alpha (\hat{{\boldsymbol{n}}})$.

  • Journal article
    Contaldi CR, 2016,

    Imaging cosmic polarization rotation

    , International Journal of Modern Physics D, Vol: 25, ISSN: 0218-2718

    We introduce a method to isolate the contribution of parity-violating modes to the peak constrained correlation function. This method can be used as a local estimate of polarization rotation. We test this method using simulations and by applying it to Planck maps [P. A. R. Ade et al., arXiv:1502.01589 astro.ph.co]. We obtain a constraint on the monopole of the polarization rotation angle α=0.31±0.23α=0.31±0.23.

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