| 1. |
- Ade, Peter, et al.
(författare)
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The Simons Observatory : science goals and forecasts
- 2019
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :2
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Tidskriftsartikel (refereegranskat)abstract
- The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands centered at: 27, 39, 93, 145, 225 and 280 GHz. The initial con figuration of SO will have three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The small aperture telescopes will target the largest angular scales observable from Chile, mapping approximate to 10% of the sky to a white noise level of 2 mu K-arcmin in combined 93 and 145 GHz bands, to measure the primordial tensor-to-scalar ratio, r, at a target level of sigma(r) = 0.003. The large aperture telescope will map approximate to 40% of the sky at arcminute angular resolution to an expected white noise level of 6 mu K-arcmin in combined 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope sky region and partially with the Dark Energy Spectroscopic Instrument. With up to an order of magnitude lower polarization noise than maps from the Planck satellite, the high-resolution sky maps will constrain cosmological parameters derived from the damping tail, gravitational lensing of the microwave background, the primordial bispectrum, and the thermal and kinematic Sunyaev-Zel'dovich effects, and will aid in delensing the large-angle polarization signal to measure the tensor-to-scalar ratio. The survey will also provide a legacy catalog of 16,000 galaxy clusters and more than 20,000 extragalactic sources.
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| 2. |
- Alsing, Justin, et al.
(författare)
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Fast likelihood-free cosmology with neural density estimators and active learning
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 488:3, s. 4440-4458
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Tidskriftsartikel (refereegranskat)abstract
- Likelihood-free inference provides a framework for performing rigorous Bayesian inference using only forward simulations, properly accounting for all physical and observational effects that can be successfully included in the simulations, The key challenge for likelihood-free applications in cosmology, where simulation is typically expensive, is developing methods that can achieve high-fidelity posterior inference with as few simulations as possible. Density estimation likelihood-free inference (DELFI) methods turn inference into a density-estimation task on a set of simulated data-parameter pairs, and give orders of magnitude improvements over traditional Approximate Bayesian Computation approaches to likelihood-free inference. In this paper, we use neural density estimators (NDEs) to learn the likelihood function from a set of simulated data sets, with active learning to adaptively acquire simulations in the most relevant regions of parameter space on the fly. We demonstrate the approach on a number of cosmological case studies, showing that for typical problems high-fidelity posterior inference can be achieved with just 0(103) simulations or fewer. In addition to enabling efficient simulation-based inference, for simple problems where the form of the likelihood is known, DELFI offers a fast alternative to Markov Chain Monte Carlo (MCMC) sampling, giving orders of magnitude speed-up in some cases. Finally, we introduce PYDELFI a flexible public implementation of DELFI with NDFs and active learning - available at haps://github.com/justinalsing/pydelfi.
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| 3. |
- Bellm, Eric C., et al.
(författare)
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The Zwicky Transient Facility : System Overview, Performance, and First Results
- 2019
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Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:995
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Tidskriftsartikel (refereegranskat)abstract
- The Zwicky Transient Facility (ZTF) is a new optical time-domain survey that uses the Palomar 48 inch Schmidt telescope. A custom-built wide-field camera provides a 47 deg(2) field of view and 8 s readout time, yielding more than an order of magnitude improvement in survey speed relative to its predecessor survey, the Palomar Transient Factory. We describe the design and implementation of the camera and observing system. The ZTF data system at the Infrared Processing and Analysis Center provides near-real-time reduction to identify moving and varying objects. We outline the analysis pipelines, data products, and associated archive. Finally, we present on-sky performance analysis and first scientific results from commissioning and the early survey. ZTF's public alert stream will serve as a useful precursor for that of the Large Synoptic Survey Telescope.
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| 4. |
- Feeney, Patrick, et al.
(författare)
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Consensus statement : Eriksholm workshop on wideband absorbance measures of the middle ear
- 2013
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Ingår i: Ear and Hearing. - : Lippincott Williams & Wilkins. - 0196-0202 .- 1538-4667. ; 34:Supplement 1, s. 78s-79s
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Tidskriftsartikel (refereegranskat)abstract
- The participants in the Eriksholm Workshop on Wideband Absorbance Measures of the Middle Ear developed statements for this consensus article on the final morning of the Workshop. The presentations of the first 2 days of the Workshop motivated the discussion on that day. The article is divided into three general areas: terminology; research needs; and clinical application.The varied terminology in the area was seen as potentially confusing, and there was consensus on adopting an organizational structure that grouped the family of measures into the term wideband acoustic immittance (WAI), and dropped the term transmittance in favor of absorbance. There is clearly still a need to conduct research on WAI measurements. Several areas of research were emphasized, including the establishment of a greater WAI normative database, especially developmental norms, and more data on a variety of disorders; increased research on the temporal aspects of WAI; and methods to ensure the validity of test data. The area of clinical application will require training of clinicians in WAI technology. The clinical implementation of WAI would be facilitated by developing feature detectors for various pathologies that, for example, might combine data across ear-canal pressures or probe frequencies.
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| 5. |
- Feeney, Stephen M., et al.
(författare)
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Clarifying the Hubble constant tension with a Bayesian hierarchical model of the local distance ladder
- 2018
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 476:3, s. 3861-3882
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Tidskriftsartikel (refereegranskat)abstract
- Estimates of the Hubble constant, H-0, from the local distance ladder and from the cosmic microwave background (CMB) are discrepant at the similar to 3 sigma level, indicating a potential issue with the standard Lambda cold dark matter (Lambda CDM) cosmology. A probabilistic (i.e. Bayesian) interpretation of this tension requires a model comparison calculation, which in turn depends strongly on the tails of the H-0 likelihoods. Evaluating the tails of the local H-0 likelihood requires the use of non-Gaussian distributions to faithfully represent anchor likelihoods and outliers, and simultaneous fitting of the complete distance-ladder data set to ensure correct uncertainty propagation. We have hence developed a Bayesian hierarchical model of the full distance ladder that does not rely on Gaussian distributions and allows outliers to be modelled without arbitrary data cuts. Marginalizing over the full similar to 3000-parameter joint posterior distribution, we find H-0 =(72.72 +/- 1.67) km s(-1) Mpc(-1) when applied to the outlier-cleaned Riess et al. data, and (73.15 +/- 1.78) km s(-1) Mpc(-1) with supernova outliers reintroduced (the pre-cut Cepheid data set is not available). Using our precise evaluation of the tails of the H-0 likelihood, we apply Bayesian model comparison to assess the evidence for deviation from Lambda CDM given the distance-ladder and CMB data. The odds against Lambda CDM are at worst similar to 10:1 when considering the Planck 2015 XIII data, regardless of outlier treatment, considerably less dramatic than naively implied by the 2.8 sigma discrepancy. These odds become similar to 60:1 when an approximation to the more-discrepant Planck Intermediate XLVI likelihood is included.
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| 6. |
- Feeney, Stephen M., et al.
(författare)
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Cosmic microwave background science at commercial airline altitudes
- 2017
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966 .- 1745-3925 .- 1745-3933. ; 469:1, s. l6-L10
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Tidskriftsartikel (refereegranskat)abstract
- Obtaining high-sensitivity measurements of degree-scale cosmic microwave background (CMB) polarization is the most direct path to detecting primordial gravitational waves. Robustly recovering any primordial signal from the dominant foreground emission will require high-fidelity observations at multiple frequencies, with excellent control of systematics. We explore the potential for a new platform for CMB observations, the Airlander 10 hybrid air vehicle, to perform this task. We show that the Airlander 10 platform, operating at commercial airline altitudes, is well suited to mapping frequencies above 220 GHz, which are critical for cleaning CMB maps of dust emission. Optimizing the distribution of detectors across frequencies, we forecast the ability of Airlander 10 to clean foregrounds of varying complexity as a function of altitude, demonstrating its complementarity with both existing (Planck) and ongoing (C-BASS) foreground observations. This novel platform could play a key role in defining our ultimate view of the polarized microwave sky.
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| 7. |
- Feeney, Stephen M., et al.
(författare)
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Prospects for Measuring the Hubble Constant with Neutron-Star-Black-Hole Mergers
- 2021
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 126:17
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Tidskriftsartikel (refereegranskat)abstract
- Gravitational wave (GW) and electromagnetic (EM) observations of neutron-star-black-hole (NSBH) mergers can provide precise local measurements of the Hubble constant (H-0), ideal for resolving the current H-0 tension. We perform end-to-end analyses of realistic populations of simulated NSBHs, incorporating both GW and EM selection for the first time. We show that NSBHs could achieve unbiased 1.5%-2.4% precision H-0 estimates by 2030. The achievable precision is strongly affected by the details of spin precession and tidal disruption, highlighting the need for improved modeling of NSBH mergers.
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| 8. |
- Feeney, Stephen M., et al.
(författare)
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Prospects for Resolving the Hubble Constant Tension with Standard Sirens
- 2019
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 122:6
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Tidskriftsartikel (refereegranskat)abstract
- The Hubble constant (H-0) estimated from the local Cepheid-supernova distance ladder is in 3-sigma tension with the value extrapolated from cosmic microwave background (CMB) data assuming the standard cosmological model. Whether this tension represents newphysics or systematic effects is the subject of intense debate. Here, we investigate how new, independent H-0 estimates can arbitrate this tension, assessing whether the measurements are consistent with being derived from the same model using the posterior predictive distribution (PPD). We show that, with existing data, the inverse distance ladder formed from BOSS baryon acoustic oscillation measurements and the Pantheon supernova sample yields an H-0 posterior near identical to the Planck CMB measurement. The observed local distance ladder value is a very unlikely draw from the resulting PPD. Turning to the future, we find that a sample of similar to 50 binary neutron star standard sirens (detectable within the next decade) will be able to adjudicate between the local and CMB estimates.
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| 9. |
- Gerardi, Francesca, et al.
(författare)
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Unbiased likelihood-free inference of the Hubble constant from light standard sirens
- 2021
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Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 104:8
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Tidskriftsartikel (refereegranskat)abstract
- Multimessenger observations of binary neutron star mergers offer a promising path toward resolution of the Hubble constant (H0) tension, provided their constraints are shown to be free from systematics such as the Malmquist bias. In the traditional Bayesian framework, accounting for selection effects in the likelihood requires calculation of the expected number (or fraction) of detections as a function of the parameters describing the population and cosmology; a potentially costly and/or inaccurate process. This calculation can, however, be bypassed completely by performing the inference in a framework in which the likelihood is never explicitly calculated, but instead fit using forward simulations of the data, which naturally include the selection. This is likelihood-free inference (LFI). Here, we use density-estimation LFI, coupled to neural-network-based data compression, to infer H0 from mock catalogues of binary neutron star mergers, given noisy redshift, distance and peculiar velocity estimates for each object. We demonstrate that LFI yields statistically unbiased estimates of H0 in the presence of selection effects, with precision matching that of sampling the full Bayesian hierarchical model. Marginalizing over the bias increases the H0 uncertainty by only 6% for training sets consisting of O(104) populations. The resulting LFI framework is applicable to population-level inference problems with selection effects across astrophysics.
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| 10. |
- Mortlock, Daniel J., et al.
(författare)
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Unbiased Hubble constant estimation from binary neutron star mergers
- 2019
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Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 100:10
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Tidskriftsartikel (refereegranskat)abstract
- Gravitational-wave (GW) observations of binary neutron star (BNS) mergers can be used to measure luminosity distances and hence, when coupled with estimates for the mergers' host redshifts, infer the Hubble constant H-0. These observations are, however, affected by GW measurement noise, uncertainties in host redshifts and peculiar velocities, and are potentially biased by selection effects and the misspecification of the cosmological model or the BNS population. The estimation of H-0 from samples of BNS mergers with optical counterparts is tested here by using a phenomenological model for the GW strains that captures both the data-driven event selection and the distance-inclination degeneracy, while being simple enough to facilitate large numbers of simulations. A rigorous Bayesian approach to analyzing the data from such simulated BNS merger samples is shown to yield results that are unbiased, have the appropriate uncertainties, and arc robust to model misspecification. Applying such methods to a sample of N similar or equal to 50 BNS merger events, as LIGO + Virgo could produce in the next similar to 5 years, should yield robust and accurate Hubble constant estimates that are precise to a level of less than or similar to 2 km s(-1) Mpc(-1), sufficient to reliably resolve the current tension between local and cosmological measurements of H-0.
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