2025/10/31 by Raagini Patki, Nicholas Battaglia, Patki, Raagini +3 · 1 citation
Physics and Astronomy · Computer Science · #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Computational Physics and Python Applications
paper · pdf · doi:10.48550/arxiv.2510.27605
We present a new method for measuring the EG statistic that combines two CMB secondaries -- the kinematic Sunyaev-Zeldovich (kSZ) effect and CMB lensing -- for the first time to probe gravity on linear scales. The EG statistic is a discriminating tool for modified gravity theories, which leave imprints in lensing observables and peculiar velocities. Existing EG measurements rely on redshift space distortions (RSD) to infer the velocity field. Here, we employ kSZ velocity-reconstruction instead of RSD, a complementary technique that constrains the largest-scale modes better than the galaxy survey it uses. We construct a novel \widehatVG estimator that involves a ratio between cross-correlations of a galaxy sample with a CMB convergence map and that with a 3D kSZ-reconstructed velocity field. We forecast for current and upcoming CMB maps from the Atacama Cosmology Telescope (ACT) and the Simons Observatory (SO), respectively, in combination with three spectroscopic galaxy samples from the Dark Energy Spectroscopic Instrument (DESI). We find cumulative detection significances in the range S/N ∼ 20-55, which can robustly test the scale-independent EG prediction under general relativity (GR) at different effective redshifts of the galaxy samples (z≈ 0.73, 1.33, 1.84). In particular, the SO×DESI LRG measurement would be able to distinguish between GR and certain modified gravity models, including Hu-Sawicki f(R) and Chameleon theories, with high confidence. The proposed \widehatVG estimator opens up a new avenue for stress-testing gravity and the ΛCDM+GR model at the largest observable scales.