The Atacama Cosmology Telescope: Reionization kSZ trispectrum methodology and limits
Abstract
Patchy reionization generates kinematic Sunyaev-Zeldovich (kSZ) anisotropies in the cosmic microwave background (CMB). Large-scale velocity perturbations along the line of sight modulate the small-scale kSZ power spectrum, leading to a trispectrum (or four-point function) in the CMB that depends on the physics of reionization. We investigate the challenges in detecting this trispectrum and use tools developed for CMB lensing, such as realization-dependent bias subtraction and cross-correlation based estimators, to counter uncertainties in the instrumental noise and assumed CMB power spectrum. We also find that both lensing and extragalactic foregrounds can impart larger trispectrum contributions than the reionization kSZ signal. We present a range of mitigation methods for both of these sources of contamination, validated on microwave-sky simulations. We use ACT DR6 and Planck data to calculate an upper limit on the reionization kSZ trispectrum from a measurement dominated by foregrounds. The upper limit is about 50 times the signal predicted from recent simulations.
Keywords
Cite
@article{arxiv.2405.01188,
title = {The Atacama Cosmology Telescope: Reionization kSZ trispectrum methodology and limits},
author = {Niall MacCrann and Frank J. Qu and Toshiya Namikawa and Boris Bolliet and Hongbo Cai and Erminia Calabrese and Steve K. Choi and Omar Darwish and Simone Ferraro and Yilun Guan and J. Colin Hill and Matt Hilton and Renée Hložek and Darby Kramer and Mathew S. Madhavacheril and Kavilan Moodley and Neelima Sehgal and Blake D. Sherwin and Cristóbal Sifón and Suzanne T. Staggs and Hy Trac and Alexander Van Engelen and Eve M. Vavagiakis},
journal= {arXiv preprint arXiv:2405.01188},
year = {2024}
}
Comments
Measurements and covariances will be made public upon publication