LiteBIRD science goals and forecasts. Mapping the hot gas in the Universe
Authors: Remazeilles M. , Douspis M. , Rubiño-Martín J.A. , Banday A.J. , Chluba J. , de Bernardis P. , De Petris M. , Hernández-Monteagudo C. , Luzzi G. , Macias-Perez J. , Masi S. , Namikawa T. , Salvati L. , Tanimura H. , Aizawa K. , Anand A. , Aumont J. , Baccigalupi C. , Ballardini M. , Barreiro R.B. , Bartolo N. , Basak S. , Bersanelli M. , Blinov D. , Bortolami M. , Brinckmann T. , Calabrese E. , Campeti P. , Carinos E. , Carones A. , Casas F.J. , Cheung K. , Clermont L. , Columbro F. , Coppolecchia A. , Cuttaia F. , de Haan T. , de la Hoz E. , Della Torre S. , Diego-Palazuelos P. , D'Alessandro G. , Eriksen H.K. , Finelli F. , Fuskeland U. , Galloni G. , Galloway M. , Gervasi M. , Génova-Santos R.T. , Ghigna T. , Giardiello S. , Gimeno-Amo C. , Gjerløw E. , González González R. , Gruppuso A. , Hazumi M. , Henrot-Versillé S. , Hergt L.T. , Herranz D. , Kohri K. , Komatsu E. , Lamagna L. , Lattanzi M. , Leloup C. , Levrier F. , Lonappan A.I. , López-Caniego M. , Maffei B. , Martínez-González E. , Matarrese S. , Matsumura T. , Micheli S. , Migliaccio M. , Monelli M. , Montier L. , Morgante G. , Nagano Y. , Nagata R. , Novelli A. , Omae R. , Pagano L. , Paoletti D. , Pavlidou V. , Piacentini F. , Pinchera M. , Polenta G. , Porcelli L. , Ritacco A. , Ruiz-Granda M. , Sakurai Y. , Scott D. , Shiraishi M. , Stever S.L. , Sullivan R.M. , Takase Y. , Tassis K. , Terenzi L. , Tomasi M. , Tristram M. , Vacher L. , van Tent B. , Vielva P. , Wehus I.K. , Westbrook B. , Weymann-Despres G. , Wollack E.J. , Zannoni M. , Zhou Y. ,   The LiteBIRD collaboration
Published: December 2024

Abstract
We assess the capabilities of the LiteBIRD mission to map the hot gas distribution
in the Universe through the thermal Sunyaev-Zeldovich (SZ) effect. Our analysis relies on
comprehensive simulations incorporating various sources of Galactic and extragalactic foreground
emission, while accounting for the specific instrumental characteristics of the LiteBIRD
mission, such as detector sensitivities, frequency-dependent beam convolution, inhomogeneous sky
scanning, and 1/f noise. We implement a tailored component-separation pipeline to map the
thermal SZ Compton y-parameter over 98% of the sky. Despite lower angular resolution for galaxy
cluster science, LiteBIRD provides full-sky coverage and, compared to the Planck
satellite, enhanced sensitivity, as well as more frequency bands to enable the construction of an
all-sky thermal SZ y-map, with reduced foreground contamination at large and intermediate
angular scales. By combining LiteBIRD and Planck channels in the
component-separation pipeline, we also obtain an optimal y-map that leverages the advantages of
both experiments, with the higher angular resolution of the Planck channels enabling the
recovery of compact clusters beyond the LiteBIRD beam limitations, and the numerous
sensitive LiteBIRD channels further mitigating foregrounds. The added value of
LiteBIRD is highlighted through the examination of maps, power spectra, and one-point
statistics of the various sky components. After component separation, the 1/f noise from
LiteBIRD's intensity channels is effectively mitigated below the level of the thermal SZ
signal at all multipoles. Cosmological constraints on S
8 = σ
8 (Ωm
/0.3)0.5 obtained from the LiteBIRD-Planck combined y-map power
spectrum exhibits a 15 % reduction in uncertainty compared to constraints derived from
Planck alone. This improvement can be attributed to the increased portion of uncontaminated
sky available in the LiteBIRD-Planck combined y-map.