Accurate Shear Recovery with Multi-Band Images of Hyper Suprime-Cam

TL;DR

This paper demonstrates that multi-band shear measurements using the Fourier_Quad method on Hyper Suprime-Cam data improve weak lensing analysis accuracy and precision by combining information across different optical bands.

Contribution

The study applies Fourier_Quad to multi-band HSC data, showing improved shear measurement accuracy and reduced errors in galaxy-galaxy lensing by combining bands.

Findings

All five bands pass the field-distortion test with high accuracy.

Combining shear catalogs from multiple bands reduces error bars in lensing measurements by about 15%.

Multi-band shear measurement enhances statistical power in weak lensing studies.

Abstract

The existing large scale weak lensing surveys typically reserve the best seeing conditions for a certain optical band to minimize shape measurement errors and maximize the number of usable background galaxies. This is because most popular shear measurement methods contain explicit or implicit thresholds on the galaxy-to-PSF (point spread function) size ratio, below which their shape measurement errors increase abruptly. Using the DECaLS data, we have previously demonstrated that the Fourier\_Quad method performs very well on poorly resolved galaxy images in general. It is therefore a ready tool for shear measurement with multi-band images regardless of their seeing conditions. In this paper, we apply the Fourier\_Quad pipeline on the multi-band images from the third public data release of the Hyper Suprime-Cam Subaru Strategic Program. We show that the shear catalogs from the five optical bands (g/r/i/z/y) all pass the field-distortion test with very high accuracy. Using the LOWZ and CMASS galaxies as foreground lenses, we show that the errorbar in the galaxy-galaxy lensing measurement can be decreased by factors around 15\% by combining shear catalogs from different bands. This indicates that it is worthful to do multi-bands shear measurements for a better shear statistics.