| 研究実績の概要 |
I finished producing the the galaxy shear catalog that will be used for the three-year cosmological weak gravitational lensing analyses using data from the Wide layer of the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) Survey. The galaxy shapes are measured from the i-band imaging data acquired from 2014 to 2019 and calibrated with image simulations that resemble the observing conditions of the survey based on training galaxy images from the Hubble Space Telescope in the COSMOS region. The catalog covers an area of 433.48 square deg of the northern sky, split into six fields. The mean i-band seeing is 0.59 arcsec. With conservative galaxy selection criteria, the observedraw galaxy number density is 22.9 per square arcmin, and the effective galaxy number density is 19.9 per square arcmin. I calibrated the galaxy property-dependent shear estimation bias to a level: multiplicative bias `m < 0.01`. The bias residual shows no dependence on redshift in the range from 0 to 3. I defined the requirements for cosmological weak lensing science for this shear catalog, and quantified potential systematics in the catalog using a series of internal null tests for systematics related to point-spread function modelling and shear estimation. A variety of the null tests are statistically consistent with zero or within requirements.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
I had several contributions to the Hyper Suprime-Cam (HSC) three-year science. I produced the weak-lensing shear catalog that will be used for the HSC three year science. A variety of the null tests have been conducted on the shear catalog and they are statistically consistent with zero or within requirements. I also prepared for the cosmological constrains based on two-point correlation functions of cosmic shear for the three-year HSC weak lensing sceience.
I made many important progresses in developing a fast and accurate shear estimation algorithm. I analytically derived the linear shear responses of several galaxy properties (e.g., ellipticity and flux) constructed with shapelet modes. In addition, I derive the covariance of photon noise on these properties with the assumption that photon noise is homogeneous Gaussian field at the scale of a galaxy image.
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| 今後の研究の推進方策 |
I will further improve the analytical shear estimator to correct for the biases from source detection. To be more specific, I will analytically derive both the linear responses of image pixel values and galaxy properties to small shear distortion. With these responses, I will be able to correct for the biases from detection, if the detection is based on the pixel values, and/or galaxy sample selection, using the galaxy properties. In addition, covariance matrix of measurement errors from photon noise on pixel values and galaxy properties can be derived with an assumption that the photon noise on images is homogeneous Gaussian. Biases induced by the photon noise in the detection process can also be corrected analytically.
I will finish the cosmic shear project using the three-year HSC shear catalog. I will perform the standard Bayesian likelihood analysis for cosmological inference from the measured cosmic shear two-point correlation functions, including contributions from intrinsic alignment of galaxies as well as systematic effects from PSF model errors, shear calibration uncertainty, and source redshift distribution errors. I will compute the covariance of cosmic shear two-point correlation function from realistic mock catalogs constructed from full-sky gravitational lensing simulations that fully account for survey geometry and measurement noise.
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