Almanac: Generic Field Level Inference for Full-Sky Cosmological Fields and Angular Power Spectra

by Dr Arthur Loureiro

Thursday 19 Jan 2023, 11:00 → 12:00 Europe/Stockholm

AlbaNova A5:1041 - CoPS grupprum (AlbaNova Main Building)

With the advent of Euclid, LSST, Simons Observatory and other upcoming Stage-IV Surveys, we will soon map cosmic structure at an unprecedented precision over a large portion of the sky, such that sky curvature becomes influential. In this talk, I will present Almanac: a generic Bayesian solution for inferring the full-sky underlying cosmological fields and their power spectra from noisy partial sky observations. The crux to inferring these science-ready data products is to develop a Monte Carlo sampler that can handle the high resolution of upcoming data maps. A further challenge is that cosmological structures often have power spectra spanning many orders of magnitude. Thus, Almanac handles strongly scale-dependent signal-to-noise cases for spin-0 and spin-2 cosmological fields.
This talk will show different applications of Almanac, focusing on the challenging applications to upcoming Weak Lensing data – presented in Loureiro et al. 2022 (ArXiv:2210.13260). Using a Euclid-like survey as a test study, we jointly infer all-sky E-mode and B-mode tomographic auto- and cross-power spectra from the masked sky and potentially parity-violating EB-mode power spectra. In this test, we probe scales up to a maximum multipole of 2048 – a Hamiltonian Monte Carlo with a total of ~16.8 Million parameters. The main output and natural outcome is the set of samples of the posterior, which does not suffer from leakage of power from E to B unless reduced to point estimates.