Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where J. Carron is active.

Publication


Featured researches published by J. Carron.


Physical Review D | 2017

Full covariance of CMB and lensing reconstruction power spectra

J. Peloton; Marcel Schmittfull; Antony Lewis; J. Carron; Oliver Zahn

CMB and lensing reconstruction power spectra are powerful probes of cosmology. However, they are correlated, since the CMB power spectra are lensed, and the lensing reconstruction is constructed using CMB multipoles. We perform a full analysis of the auto- and cross-covariances, including polarization power spectra and minimum-variance lensing estimators, and compare with simulations of idealized future CMBS4 observations. Covariances sourced by fluctuations in the unlensed CMB and instrumental noise can largely be removed by using a realization-dependent subtraction of lensing reconstruction noise, leaving a relatively simple covariance model that is dominated by lensing-induced terms and well described by a small number of principal components. The correlations between the CMB and lensing power spectra will be detectable at the level of ∼5σ for a CMB-S4 mission, and neglecting them could underestimate some parameter error bars by several tens of percent. However, we found that the inclusion of external priors or data sets to estimate parameter error bars can make the impact of the correlations almost negligible.


Physical Review D | 2017

Maximum a posteriori CMB lensing reconstruction

J. Carron; Antony Lewis

Gravitational lensing of the cosmic microwave background (CMB) is a valuable cosmological signal that correlates to tracers of large-scale structure and acts as a important source of confusion for primordial B-mode polarization. State-of-the-art lensing reconstruction analyses use quadratic estimators, which are easily applicable to data. However, these estimators are known to be suboptimal, in particular for polarization, and large improvements are expected to be possible for high signal-to-noise polarization experiments. We develop a method and numerical code, LensIt, that is able to find efficiently the most probable lensing map, introducing no significant approximations to the lensed CMB likelihood, and applicable to beamed and masked data with inhomogeneous noise. It works by iteratively reconstructing the primordial unlensed CMB using a deflection estimate and its inverse, and removing residual lensing from these maps with quadratic estimator techniques. Roughly linear computational cost is maintained due to fast convergence of iterative searches, combined with the local nature of lensing. The method achieves the maximal improvement in signal to noise expected from analytical considerations on the unmasked parts of the sky. Delensing with this optimal map leads to forecast tensor-to-scalar ratio parameter errors improved by a factor ≃2 compared to the quadratic estimator in a CMB stage IV configuration.


Journal of Cosmology and Astroparticle Physics | 2017

Internal delensing of Planck CMB temperature and polarization

J. Carron; Antony Lewis; A. Challinor


arXiv: Cosmology and Nongalactic Astrophysics | 2018

Planck 2018 results. VIII. Gravitational lensing

N. Aghanim; Y. Akrami; M. Ashdown; J. Aumont; C. Baccigalupi; M. Ballardini; A. J. Banday; R. B. Barreiro; Nicola Bartolo; S. Basak; K. Benabed; J.-P. Bernard; M. Bersanelli; P. Bielewicz; J. J. Bock; J. Borrill; F. R. Bouchet; F. Boulanger; M. Bucher; C. Burigana; E. Calabrese; J-F Cardoso; J. Carron; A. Challinor; H. C. Chiang; L. P. L. Colombo; C. Combet; B. P. Crill; F. Cuttaia; Paolo de Bernardis

Collaboration


Dive into the J. Carron's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar

A. Challinor

University of Cambridge

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

M. Ashdown

University of Cambridge

View shared research outputs
Top Co-Authors

Avatar

B. P. Crill

California Institute of Technology

View shared research outputs
Top Co-Authors

Avatar

J. Borrill

Lawrence Berkeley National Laboratory

View shared research outputs
Top Co-Authors

Avatar

J. J. Bock

California Institute of Technology

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

L. P. L. Colombo

California Institute of Technology

View shared research outputs
Top Co-Authors

Avatar

Marcel Schmittfull

Lawrence Berkeley National Laboratory

View shared research outputs
Researchain Logo
Decentralizing Knowledge