Weak lensing measurements in simulations of radio images

Patel, Prina; Abdalla, F. B.; Bacon, David; Rowe, Barnaby; Smirnov, O.; Beswick, R.

doi:10.1093/mnras/stu1588

Cited by 12 publications

(10 citation statements)

References 28 publications

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“…Weak lensing has stringent requirements on image fidelity because source ellipticities must be measured accurately in order for errors on cosmological parameters to be dominated by statistics, rather than systematics. An investigation using images simulated through a radio pipeline presented in Patel et al (2014), for e-MERLIN and LOFAR, and used in Patel et al (2015) for SKA1, shows that current iterative deconvolution methods produce images with structures in the residuals that dominate the cosmological signal, producing an analysis-induced bias far from what is required.…”

Section: Introductionmentioning

confidence: 99%

Radio weak lensing shear measurement in the visibility domain – I. Methodology

Rivi

Miller

Makhathini

et al. 2016

Mon. Not. R. Astron. Soc.

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The high sensitivity of the new generation of radio telescopes such as the Square Kilometre Array (SKA) will allow cosmological weak lensing measurements at radio wavelengths that are competitive with optical surveys. We present an adaptation to radio data of lensfit, a method for galaxy shape measurement originally developed and used for optical weak lensing surveys. This likelihood method uses an analytical galaxy model and makes a Bayesian marginalisation of the likelihood over uninteresting parameters. It has the feature of working directly in the visibility domain, which is the natural approach to adopt with radio interferometer data, avoiding systematics introduced by the imaging process. As a proof of concept, we provide results for visibility simulations of individual galaxies with flux density S 10µJy at the phase centre of the proposed SKA1-MID baseline configuration, adopting 12 frequency channels in the band 950 -1190 MHz. Weak lensing shear measurements from a population of galaxies with realistic flux and scalelength distributions are obtained after natural gridding of the raw visibilities. Shear measurements are expected to be affected by 'noise bias': we estimate the bias in the method as a function of signal-to-noise ratio (SNR). We obtain additive and multiplicative bias values that are comparable to SKA1 requirements for SNR > 18 and SNR > 30, respectively. The multiplicative bias for SNR > 10 is comparable to that found in ground-based optical surveys such as CFHTLenS, and we anticipate that similar shear measurement calibration strategies to those used for optical surveys may be used to good effect in the analysis of SKA radio interferometer data.

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Section: Introductionmentioning

confidence: 99%

Radio weak lensing shear measurement in the visibility domain – I. Methodology

Rivi

Miller

Makhathini

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Chang et al (2004) take advantage of the shapelet basis functions being invariant under Fourier transform, and perform the shear measurement directly in the uv plane. Recent simulated images by Patel et al (2014) for eMERLIN suggest values of m = 0.176 and c = 0.006 are achievable with the shapelets in the image domain. For the first phase of the SKA, Patel et al (2015) find that m = 0.28 and c = 0.001 is achievable using similar techniques, although the requirements are considerably lower: m < 0.0054 and c < 0.0073.…”

Section: Pos(extra-radsur2015)031mentioning

confidence: 99%

Weak lensing with radio continuum surveys

Patel¹

2016

Proceedings of the Many Facets of Extragalactic Radio Surveys: Towards New Scientific Challenges — PoS(EXTRA-RADSUR2015)

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Weak gravitational lensing is a powerful probe of cosmology and has emerged as a key probe for the Dark Universe. Up till now this science has been conducted mainly at optical wavelengths. Current upgraded and future radio facilities will provide greatly improved data that will allow lensing measurements to be made at these longer wavelengths. In this proceedings I show how the larger facilities such as the SKA can produce game changing cosmological measurements even compared to future optical telescopes. I will also discuss how radio surveys can also provide unique ways in which some of the most problematic systematic errors can be mitigated through the extra information that can be provided in the form of polarisation and rotational velocity measurements. I will also demonstrate the advantages to having overlapping optical and radio weak lensing surveys and how their cross-correlation leads to a cleaner extraction of the cosmological information. Key to the realisation of the great promise of radio weak lensing is the suitable measurements of galaxy shapes in the radio data, either from images or from the visibility data. I shall end with a description of the key issues related to this matter and the radioGREAT challenge which has been proposed to address them.

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“…Patel et al (2010) use shapelets to model images reconstructed using the CLEAN algorithm, while Chang et al (2004) take advantage of the fact that shapelets remain localised analytic functions under Fourier transformation to directly model the visibility plane and were able to make a 3.6σ detection of cosmic shear. More recently, Patel et al (2013) A number of open problems still remain. Although initial steps have been taken, only a small part of the space of possible radio shear measurement techniques has so far been explored.…”

Section: Shear Measurementmentioning

confidence: 99%

Weak gravitational lensing with the Square Kilometre Array

Brown¹,

Bacon²,

Camera³

et al. 2015

Proceedings of Advancing Astrophysics With the Square Kilometre Array — PoS(AASKA14)

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We investigate the capabilities of various stages of the SKA to perform world-leading weak gravitational lensing surveys. We outline a way forward to develop the tools needed for pursuing weak lensing in the radio band. We identify the key analysis challenges and the key pathfinder experiments that will allow us to address them in the run up to the SKA. We identify and summarize the unique and potentially very powerful aspects of radio weak lensing surveys, facilitated by the SKA, that can solve major challenges in the field of weak lensing. These include the use of polarization and rotational velocity information to control intrinsic alignments, and the new area of weak lensing using intensity mapping experiments. We show how the SKA lensing surveys will both complement and enhance corresponding efforts in the optical wavebands through cross-correlation techniques and by way of extending the reach of weak lensing to high redshift.Advancing Astrophysics with the Square Kilometre Array

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Weak lensing measurements in simulations of radio images

Cited by 12 publications

References 28 publications

Radio weak lensing shear measurement in the visibility domain – I. Methodology

Radio weak lensing shear measurement in the visibility domain – I. Methodology

Weak lensing with radio continuum surveys

Weak gravitational lensing with the Square Kilometre Array

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