Holonic Execution: A BDI Approach

Jarvis, Jacqueline; Jarvis, Dennis; Rönnquist, Ralph; Jain, Lakhmi C.

doi:10.1007/978-3-540-77479-2

Cited by 23 publications

(25 citation statements)

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“…The reason for this is the linear response of PSF ellipticity on defocus caused by astigmatism, while PSF width responds to leading order quadratically (see e.g. Jarvis et al 2008). Given that PCA is a purely linear coordinate transformation, it is not capable to directly capture this one-parametric variation (separation between primary and secondary mirror) with a single principal component.…”

Section: B5 Principal-component Correction For the Time-dependent Amentioning

confidence: 99%

Evidence of the accelerated expansion of the Universe from weak lensing tomography with COSMOS

Schrabback

Hartlap

Joachimi

et al. 2010

A&A

344

457

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We present a comprehensive analysis of weak gravitational lensing by large-scale structure in the Hubble Space Telescope Cosmic Evolution Survey (COSMOS), in which we combine space-based galaxy shape measurements with ground-based photometric redshifts to study the redshift dependence of the lensing signal and constrain cosmological parameters. After applying our weak lensingoptimized data reduction, principal-component interpolation for the spatially, and temporally varying ACS point-spread function, and improved modelling of charge-transfer inefficiency, we measured a lensing signal that is consistent with pure gravitational modes and no significant shape systematics. We carefully estimated the statistical uncertainty from simulated COSMOS-like fields obtained from ray-tracing through the Millennium Simulation, including the full non-Gaussian sampling variance. We tested our lensing pipeline on simulated space-based data, recalibrated non-linear power spectrum corrections using the ray-tracing analysis, employed photometric redshift information to reduce potential contamination by intrinsic galaxy alignments, and marginalized over systematic uncertainties. We find that the weak lensing signal scales with redshift as expected from general relativity for a concordance ΛCDM cosmology, including the full cross-correlations between different redshift bins. Assuming a flat ΛCDM cosmology, we measure σ 8 (Ω m /0.3) 0.51 = 0.75 ± 0.08 from lensing, in perfect agreement with WMAP-5, yielding joint constraints Ω m = 0.266 +0.025 −0.023 , σ 8 = 0.802 +0.028 −0.029 (all 68.3% conf.). Dropping the assumption of flatness and using priors from the HST Key Project and Big-Bang nucleosynthesis only, we find a negative deceleration parameter q 0 at 94.3% confidence from the tomographic lensing analysis, providing independent evidence of the accelerated expansion of the Universe. For a flat wCDM cosmology and prior w ∈ [−2, 0], we obtain w < −0.41 (90% conf.). Our dark energy constraints are still relatively weak solely due to the limited area of COSMOS. However, they provide an important demonstration of the usefulness of tomographic weak lensing measurements from space.

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Section: B5 Principal-component Correction For the Time-dependent Amentioning

confidence: 99%

Evidence of the accelerated expansion of the Universe from weak lensing tomography with COSMOS

Schrabback

Hartlap

Joachimi

et al. 2010

A&A

344

457

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“…However, according to Jarvis et al (2008), models of low-order optical aberrations such as focus and astigmatism can reproduce 90% of the PSF anisotropy patterns found in real observation data. If so, physicallymotivated models could provide an alternative or a complement to purely empirical methods such as PCA.…”

Section: An Overview Of Existing Psf Interpolation Schemesmentioning

confidence: 99%

“…images were supplied as non-overlapping, randomly-scattered 48 × 48 pixels postage stamps, altered by Gaussian noise. After completion of the challenge, it was revealed the stars had either a Moffat (Moffat 1969) or pseudo-Airy (Born & Wolf 1999;Kuijken 2008) profile, with a telescope component model from Jarvis et al (2008). Depending on the sets, specific additional effects, such as Kolmogorov turbulence, were also incorporated.…”

Section: Applying Spatial Interpolation Schemes On the Great10 Star Cmentioning

confidence: 99%

Interpolating point spread function anisotropy

Gentile

Courbin

Meylan

2012

A&A

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Planned wide-field weak lensing surveys are expected to reduce the statistical errors on the shear field to unprecedented levels. In contrast, systematic errors like those induced by the convolution with the point spread function (PSF) will not benefit from that scaling effect and will require very accurate modeling and correction. While numerous methods have been devised to carry out the PSF correction itself, modeling of the PSF shape and its spatial variations across the instrument field of view has, so far, attracted much less attention. This step is nevertheless crucial because the PSF is only known at star positions while the correction has to be performed at any position on the sky. A reliable interpolation scheme is therefore mandatory and a popular approach has been to use low-order bivariate polynomials. In the present paper, we evaluate four other classical spatial interpolation methods based on splines (B-splines), inverse distance weighting (IDW), radial basis functions (RBF) and ordinary Kriging (OK). These methods are tested on the Star-challenge part of the GRavitational lEnsing Accuracy Testing 2010 (GREAT10) simulated data and are compared with the classical polynomial fitting (Polyfit). In all our methods we model the PSF using a single Moffat profile and we interpolate the fitted parameters at a set of required positions. This allowed us to win the Star-challenge of GREAT10, with the B-splines method. However, we also test all our interpolation methods independently of the way the PSF is modeled, by interpolating the GREAT10 star fields themselves (i.e., the PSF parameters are known exactly at star positions). We find in that case RBF to be the clear winner, closely followed by the other local methods, IDW and OK. The global methods, Polyfit and B-splines, are largely behind, especially in fields with (ground-based) turbulent PSFs. In fields with non-turbulent PSFs, all interpolators reach a variance on PSF systematics σ 2 sys better than the 1 × 10 −7 upper bound expected by future space-based surveys, with the local interpolators performing better than the global ones.

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“…A well-focused image is crucial for accurate shape measurements because the ellipticity of a target object in the image plane can be strongly dependent on the amount of defocus, especially in the presence of other optical aberrations-particularly astigmatism (Jarvis et al 2008). We show how our ellipticity measurements vary with defocus in § 4.3.…”

Section: Focusmentioning

confidence: 99%

“…In particular, the amount of ellipticity is proportional to the product of defocus and astigmatism (Jarvis et al 2008;Noecker 2010). In Figure 10, we plot ellipticity versus defocus, illustrating that our data are consistent with the expected trend.…”

Section: Variation Of Ellipticity With Defocusmentioning

confidence: 99%

Initial Results from a Laboratory Emulation of Weak Gravitational Lensing Measurements

Seshadri

Shapiro

Goodsall

et al. 2013

Publications of the Astronomical Society of the Pacific

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ABSTRACT. Weak gravitational lensing observations are a key science driver for the NASA Wide Field Infrared Survey Telescope (WFIRST). To validate the performance of the WFIRST infrared detectors, we have performed a laboratory emulation of weak gravitational lensing measurements. Our experiments used a custom precision projector system to image a target mask composed of a grid of pinholes, emulating stellar point sources, onto a 1.7 μm cut-off Teledyne HgCdTe/H2RG detector. We used a 0.88 μm LED illumination source and f=22 pupil stop to produce undersampled point spread functions similar to those expected from WFIRST. We also emulated the WFIRST image reconstruction strategy, using the image combination (IMCOM) algorithm to derive oversampled images from dithered, undersampled input images. We created shear maps for this data and computed shear correlation functions to mimic a real weak lensing analysis. After removing only second-order polynomial fits to the shear maps, we found that the correlation functions could be reduced to Oð10 À6 Þ. This places a conservative upper limit on the detector-induced bias to the correlation function (under our test conditions). This bias is two orders of magnitude lower than the expected weak lensing signal. Restricted to scales relevant to dark energy analyses (sky separations >0:5 0 ), the bias is Oð10 À7 Þ-comparable to the requirement for future weak lensing missions to avoid biasing cosmological parameter estimates. Our experiment will need to be upgraded and repeated under different configurations to fully characterize the shape measurement performance of WFIRST IR detectors.

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Holonic Execution: A BDI Approach

Cited by 23 publications

References 0 publications

Evidence of the accelerated expansion of the Universe from weak lensing tomography with COSMOS

Evidence of the accelerated expansion of the Universe from weak lensing tomography with COSMOS

Interpolating point spread function anisotropy

Initial Results from a Laboratory Emulation of Weak Gravitational Lensing Measurements

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