SKA weak lensing – I. Cosmological forecasts and the power of radio-optical cross-correlations

Harrison, I.; Camera, Stefano; Zuntz, J.; Brown, Michael L.

doi:10.1093/mnras/stw2082

Cited by 60 publications

(86 citation statements)

References 88 publications

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“…For this analysis, we first assume that one is not sharing data between the two surveys, but only use the final catalogs so that photo-z accuracy is the standard for each survey taken on its own. The data vector is then Harrison et al (2016), to which we refer the reader for further details. For a given ℓ, we the define the S/N as  =…”

Section: Weak-lensing S/n and Photo-z Accuracy: An Examplementioning

confidence: 99%

Scientific Synergy between LSST and Euclid

Rhodes

Nichol

Aubourg

et al. 2017

ApJS

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Euclid and the Large Synoptic Survey Telescope (LSST) are poised to dramatically change the astronomy landscape early in the next decade. The combination of high-cadence, deep, wide-field optical photometry from LSST with highresolution, wide-field optical photometry, and near-infrared photometry and spectroscopy from Euclid will be powerful for addressing a wide range of astrophysical questions. We explore Euclid/LSST synergy, ignoring the political issues associated with data access to focus on the scientific, technical, and financial benefits of coordination. We focus primarily on dark energy cosmology, but also discuss galaxy evolution, transient objects, solar system science, and galaxy cluster studies. We concentrate on synergies that require coordination in cadence or survey overlap, or would benefit from pixellevel co-processing that is beyond the scope of what is currently planned, rather than scientific programs that could be accomplished only at the catalog level without coordination in data processing or survey strategies. We provide two quantitative examples of scientific synergies: the decrease in photo-z errors (benefiting many science cases) when highresolution Euclid data are used for LSST photo-z determination, and the resulting increase in weak-lensing signal-to-noise ratio from smaller photo-z errors. We briefly discuss other areas of coordination, including high-performance computing resources and calibration data. Finally, we address concerns about the loss of independence and potential cross-checks between the two missions and the potential consequences of not collaborating.

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Section: Weak-lensing S/n and Photo-z Accuracy: An Examplementioning

confidence: 99%

Scientific Synergy between LSST and Euclid

Rhodes

Nichol

Aubourg

et al. 2017

ApJS

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“…Previously, in Harrison et al (2016) (hereafter, Paper I), we have constructed forecasts for cosmological parameter estimation. We have shown that the first phase of the SKA (SKA1) can be competitive with experiments such as the Dark Energy Survey (DES), and that the full SKA (SKA2) can potentially provide us with tighter constraints from weak lensing alone than optical cosmic shear surveys such as the Large Synoptic Survey Telescope (LSST) or the European Space Agency Euclid satellite.…”

Section: Introductionmentioning

confidence: 99%

SKA weak lensing – III. Added value of multiwavelength synergies for the mitigation of systematics

Camera

Harrison

Bonaldi

et al. 2016

Mon. Not. R. Astron. Soc.

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In this third paper of a series on radio weak lensing for cosmology with the Square Kilometre Array, we scrutinise synergies between cosmic shear measurements in the radio and optical/near-IR bands for mitigating systematic effects. We focus on three main classes of systematics: (i) experimental systematic errors in the observed shear; (ii) signal contamination by intrinsic alignments; and (iii) systematic effects due to an incorrect modelling of non-linear scales. First, we show that a comprehensive, multiwavelength analysis provides a self-calibration method for experimental systematic effects, only implying < 50% increment on the errors on cosmological parameters. We also illustrate how the cross-correlation between radio and optical/near-IR surveys alone is able to remove residual systematics with variance as large as 10 −5 , i.e. the same order of magnitude of the cosmological signal. This also opens the possibility of using such a cross-correlation as a means to detect unknown experimental systematics. Secondly, we demonstrate that, thanks to polarisation information, radio weak lensing surveys will be able to mitigate contamination by intrinsic alignments, in a way similar but fully complementary to available self-calibration methods based on position-shear correlations. Lastly, we illustrate how radio weak lensing experiments, reaching higher redshifts than those accessible to optical surveys, will probe dark energy and the growth of cosmic structures in régimes less contaminated by non-linearities in the matter perturbations. For instance, the higher-redshift bins of radio catalogues peak at z ≃ 0.8 − 1, whereas their optical/near-IR counterparts are limited to z 0.5 − 0.7. This translates into having a cosmological signal 2 to 5 times less contaminated by non-linear perturbations.

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“…The idea, suggested by Blain (2002) and Morales (2006), is to measure the departure from perpendicularity of the rotation axis of a disk galaxy to the major axis of the galaxy disk image and use this measure as an estimate of the shear field at the galaxy's position (see also Huff et al 2013). Finally, by cross-correlating the shear estimators of optical and radio surveys, uncorrelated systematic errors may be mitigated (Patel et al 2010;Demetroullas & Brown 2016;Harrison et al 2016;Camera et al 2016). For a general overview of radio weak lensing see Brown et al (2015).…”

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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SKA weak lensing – I. Cosmological forecasts and the power of radio-optical cross-correlations

Cited by 60 publications

References 88 publications

Scientific Synergy between LSST and Euclid

Scientific Synergy between LSST and Euclid

SKA weak lensing – III. Added value of multiwavelength synergies for the mitigation of systematics

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

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