Probing the Nature of Dark Matter Through Measurements of Galaxy Shapes and Redshifts

BoMee Lee (IPAC)
Friday, November 1, 2019 - 12:15pm to 1:00pm

Measuring weak gravitational lensing (WL), a powerful probe of the distribution of large scale structure, is one of the primary science goals of Euclid and other future large extragalactic surveys with LSST and WFIRST. In order to reconstruct a three dimensional weak lensing map of dark matter in different redshift bins, it is crucial to constrain both galaxy shapes and photometric redshifts very well. Currently, the WL analysis has primarily been based on optical band imaging, limiting results to z<1; Euclid and LSST will detect cosmic shear with optical imaging over many thousands of square degrees. However, near-infrared (NIR) imaging has never been used for wide-field weak lensing measurement outside of cluster fields. In this talk, first, I will present the advantages of measuring galaxy shapes in the NIR with Euclid-quality images simulated from HST images. Second, I will introduce new galaxy templates that populate three-color space and are constrained by HST/CANDELS photometry. This new template library is a powerful tool to constrain photometric redshifts for future surveyswhich will only have limited number of bands at the relevant sensitivities. I will conclude with plans for future work. These include the first z > 1 weak lensing map of dark matter distribution in a blank field with the largest set of HST archival NIR images, which will serve as a critical stepping stone for NIR shear measurements with upcoming space-based WL surveys with Euclid and WFIRST. With a joint analysis with X-ray data, this will be particularly important for calibrating masses of z > 1 clusters.

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