LiteBIRD Science Goals and Forecasts: Improving Sensitivity to Inflationary Gravitational Waves with Multitracer Delensing

• Published in: arXiv.org 2023-12
• Main Authors: Namikawa, T, Lonappan, A I, Bartolo, N, Beck, D, Benabed, K, Challinor, A, Diego-Palazuelos, P, Errard, J, Farrens, S, Gruppuso, A, Krachmalnicoff, N, Migliaccio, M, Martínez-González, E, Pettorino, V, Piccirilli, G, Sherwin, B, Starck, J, Akizawa, R, Anand, A, Aumont, J, Aurlien, R, Azzoni, S, Bersanelli, M, Bortolami, M, Brinckmann, T, Calabrese, E, Campeti, P, Carralot, F, Cheung, K, Clermont, L, Columbro, F, Conenna, G, Coppolecchia, A, Cuttaia, F, D'Alessandro, G, De Petris, M, S Della Torre, E Di Giorgi, Eriksen, H K, Finelli, F, Franceschet, C, Fuskeland, U, Galloni, G, Georges, M, Gervasi, M, Giardiello, S, Gimeno-Amo, C, Gjerløw, E, Hazumi, M, Henrot-Versillé, S, Hergt, L T, Hivon, E, Kohri, K, Komatsu, E, Lamagna, L, Lattanzi, M, Lembo, M, López-Caniego, M, Luzzi, G, Maffei, B, Masi, S, Matarrese, S, Micheli, S, Moggi, A, Monelli, M, Montier, L, Morgante, G, Mot, B, Mousset, L, Nagata, R, Natoli, P, Novelli, A, Obata, I, Occhiuzzi, A, Pagano, L, Paiella, A, Paoletti, D, Piacentini, F, Pinchera, M, Pisano, G, Polenta, G, Puglisi, G, Remazeilles, M, Ritacco, A, Rizzieri, A, Rubino-Martin, J, Scott, D, Shiraishi, M, Signorelli, G, Stever, S L, Takase, Y, Tanimura, H, Tartari, A, Tassis, K, Tristram, M, Vacher, L, B van Tent, Wehus, I K, Zhou, Y, the LiteBIRD Collaboration
• Format: Article
• Language: English
• Subjects: Gravitational waves; Sensitivity; Tensors; Tracers
• ISSN: 2331-8422

We estimate the efficiency of mitigating the lensing \(B\)-mode polarization, the so-called delensing, for the \(LiteBIRD\) experiment with multiple external data sets of lensing-mass tracers. The current best bound on the tensor-to-scalar ratio, \(r\), is limited by lensing rather than Galactic foregrounds. Delensing will be a critical step to improve sensitivity to \(r\) as measurements of \(r\) become more and more limited by lensing. In this paper, we extend the analysis of the recent \(LiteBIRD\) forecast paper to include multiple mass tracers, i.e., the CMB lensing maps from \(LiteBIRD\) and CMB-S4-like experiment, cosmic infrared background, and galaxy number density from \(Euclid\)- and LSST-like survey. We find that multi-tracer delensing will further improve the constraint on \(r\) by about \(20\%\). In \(LiteBIRD\), the residual Galactic foregrounds also significantly contribute to uncertainties of the \(B\)-modes, and delensing becomes more important if the residual foregrounds are further reduced by an improved component separation method.