The Gravitational Lensing Imprints of DES Y3 Superstructures on the CMB: A Matched Filtering Approach

Low density cosmic voids gravitationally lens the cosmic microwave background (CMB), leaving a negative imprint on the CMB convergence κ. This effect provides insight into the distribution of matter within voids, and can also be used to study the growth of structure. We measure this lensing imprint by cross-correlating the Planck CMB lensing convergence map with voids identified in the Dark Energy Survey Year 3 data set, covering approximately 4,200 deg^2 of the sky. We use two distinct void-finding algorithms: a 2D void-finder which operates on the projected galaxy density field in thin redshift shells, and a new code, Voxel, which operates on the full 3D map of galaxy positions. We employ an optimal matched filtering method for cross-correlation, using the MICE N-body simulation both to establish the template for the matched filter and to calibrate detection significances. Using the DES Y3 photometric luminous red galaxy sample, we measure A_κ, the amplitude of the observed lensing signal relative to the simulation template, obtaining A_κ = 1.03 ± 0.22 (4.6σ significance) for Voxel and A_κ = 1.02 ± 0.17 (5.9σ significance) for 2D voids, both consistent with ΛCDM expectations. We additionally invert the 2D void-finding process to identify superclusters in the projected density field, for which we measure A_κ = 0.87 ± 0.15 (5.9σ significance). The leading source of noise in our measurements is Planck noise, implying that future data from the Atacama Cosmology Telescope (ACT), South Pole Telescope (SPT) and CMB-S4 will increase sensitivity and allow for more precise measurements.