Oral Presentation

Spectroscopic Weak Lensing Tomography for Local Massive Clusters

Author(s): Jubee Sohn (Seoul National University)

Presenter: Jubee Sohn (Seoul National University)

We present spectrotomographic weak lensing measurements for three rich galaxy clusters—A2029, A1767, and A2065—using only background galaxies with spectroscopically confirmed redshifts. These clusters serve as a demonstration of the power of combining spectroscopy and lensing to derive accurate cluster masses and to mitigate biases caused by foreground contamination and photometric redshift uncertainties. We detect weak lensing signals from all three clusters at significances greater than $3.1\sigma$. The measured shear amplitudes are consistent with cluster dynamical (caustic) masses and scale appropriately with source redshift. A comparison between the spectrotomographic detection of A2029 using DECam imaging and those of A1767 and A2065 using HSC imaging highlights subtle but potentially important systematics related to the shear measurements of relatively bright background galaxies. Understanding these effects will be critical for future, more extensive applications of spectrotomography using deeper Subaru/HSC data, as well as upcoming observations from Euclid and LSST. These three detections establish a proof of concept for using spectrotomography as a robust tool for unbiased cluster mass measurements and for enabling geometric cosmological tests independent of other methods.