Tolerance For the Pixelation Effect in Shear Measurement

Shen, Zhi Xiang; Zhang, Jun; Li, Hekun; Wang, Haoran; Chi, Wei; Li, Guoliang; Li, Xiaobo; Ban, Zhang; Yue, Dan

doi:10.3847/1538-3881/ac8ff9

Cited by 4 publications

(2 citation statements)

References 30 publications

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“…It may seem strange to additionally smooth the image to mitigate sampling effects; after all, the high angular resolution is one of the reasons to build a space mission in the first place. However, it is actually quite similar to the suggestion in Kannawadi et al (2021) to use a larger weighting scale for galaxy ellipticities 13 and the convolution suggested by Shen et al (2022). And we note that the output PSFs in Table 4 are still much smaller than those obtained in ground-based surveys.…”

Section: Output Psfssupporting

confidence: 82%

Simulating image coaddition with the Nancy Grace Roman Space Telescope: I. Simulation methodology and general results

Hirata¹,

Yamamoto²,

Laliotis³

et al. 2023

Preprint

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The upcoming Nancy Grace Roman Space Telescope will carry out a wide-area survey in the near infrared. A key science objective is the measurement of cosmic structure via weak gravitational lensing. Roman data will be undersampled, which introduces new challenges in the measurement of source galaxy shapes; a potential solution is to use linear algebra-based coaddition techniques such as I that combine multiple undersampled images to produce a single oversampled output mosaic with a desired "target" point spread function (PSF). We present here an initial application of I to 0.64 square degrees of simulated Roman data, based on the Roman branch of the Legacy Survey of Space and Time (LSST) Dark Energy Science Collaboration (DESC) Data Challenge 2 (DC2) simulation. We show that I runs successfully on simulated data that includes features such as plate scale distortions, chip gaps, detector defects, and cosmic ray masks. We simultaneously propagate grids of injected sources and simulated noise fields as well as the full simulation. We quantify the residual deviations of the PSF from the target (the "fidelity"), as well as noise properties of the output images; we discuss how the overall tiling pattern as well as Moiré patterns appear in the final fidelity and noise maps. We include appendices on interpolation algorithms and the interaction of undersampling with image processing operations that may be of broader applicability. The companion paper ("Paper II") explores the implications for weak lensing analyses.

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Section: Output Psfssupporting

confidence: 82%

Simulating image coaddition with the Nancy Grace Roman Space Telescope: I. Simulation methodology and general results

Hirata¹,

Yamamoto²,

Laliotis³

et al. 2023

Preprint

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show abstract

“…The wavelength sampling interval is 1 nm. The PSF model is simply simulated by the Airy function, which shows a similar shape to the PSF in the CSST i band (Shen et al 2022). The profile of the Airy disk is expressed as…”

Section: Color Gradient Biasmentioning

confidence: 99%

The Chromatic Point-spread Function of Weak Lensing Measurement in the Chinese Space Station Survey Telescope

Liu

Xinzhong

Liu

et al. 2023

Res. Astron. Astrophys.

Self Cite

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The weak gravitational lensing is a powerful tool in modern cosmology. To accurately measure the weak lensing signal, one has to control the systematic bias to a small level. One of the most difficult problems is how to correct the smearing effect of the Point Spread Function (PSF) on the shape of the galaxies. The chromaticity of PSF for a broad-band observation can lead to new subtle effects. Since the PSF is wavelength dependent and the spectrum energy distribution between stars and galaxies is different, the effective PSF measured from the star images will be different from that smears the galaxies. Such a bias is called colour bias. We estimate it in the optical bands of the Chinese Space Station Survey Telescope from simulated PSFs, and show the dependence on the colour and redshift of the galaxies. Moreover, due to the spatial variation of spectra over the galaxy image, there exists another higher-order bias, colour gradient bias. Our results show that both colour bias and colour gradient bias are generally below 0.1 percent in CSST. Only for small-size galaxies, one needs to be careful about the colour gradient bias in the weak lensing analysis using CSST data.

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Simulating image coaddition with the Nancy Grace Roman Space Telescope – I. Simulation methodology and general results

Hirata,

Yamamoto,

Laliotis

et al. 2024

Monthly Notices of the Royal Astronomical Society

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The upcoming Nancy Grace Roman Space Telescope will carry out a wide-area survey in the near infrared. A key science objective is the measurement of cosmic structure via weak gravitational lensing. Roman data will be undersampled, which introduces new challenges in the measurement of source galaxy shapes; a potential solution is to use linear algebra-based coaddition techniques such as Imcom that combine multiple undersampled images to produce a single oversampled output mosaic with a desired “target” point spread function (PSF). We present here an initial application of Imcom to 0.64 square degrees of simulated Roman data, based on the Roman branch of the Legacy Survey of Space and Time (LSST) Dark Energy Science Collaboration (DESC) Data Challenge 2 (DC2) simulation. We show that Imcom runs successfully on simulated data that includes features such as plate scale distortions, chip gaps, detector defects, and cosmic ray masks. We simultaneously propagate grids of injected sources and simulated noise fields as well as the full simulation. We quantify the residual deviations of the PSF from the target (the “leakage”), as well as noise properties of the output images; we discuss how the overall tiling pattern as well as Moiré patterns appear in the final leakage and noise maps. We include appendices on interpolation algorithms and the interaction of undersampling with image processing operations that may be of broader applicability. The companion paper (“Paper II”) explores the implications for weak lensing analyses.

show abstract

Tolerance For the Pixelation Effect in Shear Measurement

Cited by 4 publications

References 30 publications

Simulating image coaddition with the Nancy Grace Roman Space Telescope: I. Simulation methodology and general results

Simulating image coaddition with the Nancy Grace Roman Space Telescope: I. Simulation methodology and general results

The Chromatic Point-spread Function of Weak Lensing Measurement in the Chinese Space Station Survey Telescope

Simulating image coaddition with the Nancy Grace Roman Space Telescope – I. Simulation methodology and general results

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