Tensor-to-scalar ratio forecasts for extended LiteBIRD frequency configurations

¹ Institute of Theoretical Astrophysics, University of Oslo, Blindern, Oslo, Norway
² IRAP, Université de Toulouse, CNRS, CNES, UPS, Toulouse, France
³ International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy
⁴ INFN Sezione di Trieste, Via Valerio 2, 34127 Trieste, Italy
⁵ IFPU, Via Beirut, 2, 34151 Grignano, Trieste, Italy
⁶ Université de Paris, CNRS, Astroparticule et Cosmologie, 75013 Paris, France
⁷ Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Canary Islands, Spain
⁸ Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
⁹ Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), UTIAS, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
¹⁰ NIST Quantum Sensors Group, 325 Broadway, Boulder, CO 80305, USA
¹¹ National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
¹² Dipartimento di Fisica, Università La Sapienza, P.le A. Moro 2, Roma, Italy
¹³ INFN Sezione di Roma, P.le A. Moro 2, 00185 Roma, Italy
¹⁴ University of Milano Bicocca, Physics Department, Piazza della Scienza, 3, 20126 Milano, Italy
¹⁵ INFN Sezione Milano Bicocca, Piazza della Scienza, 3, 20126 Milano, Italy
¹⁶ Instituto de Fisica de Cantabria (IFCA, CSIC-UC), Avenida los Castros s/n, 39005 Santander, Spain
¹⁷ Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
¹⁸ SLAC National Accelerator Laboratory, Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Menlo Park, CA 94025, USA
¹⁹ Stanford University, Department of Physics, Stanford, CA 94305-4060, USA
²⁰ Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
²¹ Dipartimento di Fisica e Scienze della Terra, Universitá di Ferrara, Via Saragat 1, 44122 Ferrara, Italy
²² INFN Sezione di Ferrara, Via Saragat 1, 44122 Ferrara, Italy
²³ INAF – OAS Bologna, Via Piero Gobetti, 93/3, 40129 Bologna, Italy
²⁴ Dipartimento di Fisica e Astronomia “G. Galilei”, Universitá degli Studi di Padova, Via Marzolo 8, 35131 Padova, Italy
²⁵ INFN Sezione di Padova, Via Marzolo 8, 35131 Padova, Italy
²⁶ INAF, Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
²⁷ Dipartimento di Fisica, Universitá degli Studi di Milano, Via Celoria 16, 20133 Milano, Italy
²⁸ INFN Sezione di Milano, Via Celoria 16, 20133 Milano, Italy
²⁹ School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, UK
³⁰ Dipartimento di Fisica, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica, 1, 00133 Roma, Italy
³¹ INFN Sezione di Roma2, Universitá di Roma Tor Vergata, via della Ricerca Scientifica, 1, 00133 Roma, Italy
³² University of California, Berkeley, Department of Physics, Berkeley CA 94720, USA
³³ University of California, Berkeley, Space Sciences Laboratory, Berkeley, CA 94720, USA
³⁴ Lawrence Berkeley National Laboratory (LBNL), Computational Cosmology Center, Berkeley, CA 94720, USA
³⁵ Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Stanford University, Stanford, CA 94305, USA
³⁶ Centre Spatial de Liège (STAR Institute), University of Liège, Avenue du Pré-Aily, Angleur 4031, Belgium
³⁷ Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
³⁸ International Center for Quantum-field Measurement Systems for Studies of the Universe and Particles (QUP), High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
³⁹ Dpto. de Física Moderna, Universidad de Cantabria, Avda. los Castros s/n, 39005 Santander, Spain
⁴⁰ INFN Sezione di Bologna, Viale C. Berti Pichat 6/2, 40127 Bologna, Italy
⁴¹ Tohoku University, Graduate School of Science, Astronomical Institute, Sendai 980-8578, Japan
⁴² Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS), Sagamihara, Kanagawa 252-5210, Japan
⁴³ The Graduate University for Advanced Studies (SOKENDAI), Miura District, Kanagawa, 240-0115 Hayama, Japan
⁴⁴ Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver BC V6T1Z1, Canada
⁴⁵ Institut d’Astrophysique de Paris, CNRS/Sorbonne Université, Paris, France
⁴⁶ Lawrence Berkeley National Laboratory (LBNL), Physics Division, Berkeley, CA 94720, USA
⁴⁷ Laboratoire de Physique de l’École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, 75005 Paris, France
⁴⁸ Space Science Data Center, Italian Space Agency, Via del Politecnico, 00133 Roma, Italy
⁴⁹ Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, 91405 Orsay, France
⁵⁰ Gran Sasso Science Institute (GSSI), Viale F. Crispi 7, 67100 L’Aquila, Italy
⁵¹ David A. Dunlap Department of Astronomy and Astrophysics, 50 St. George Street, Toronto, ON M5S3H4, Canada
⁵² Institute of Astrophysics, Foundation for Research and Technology-Hellas, Vasilika Vouton, 70013 Heraklion, Greece
⁵³ Department of Physics and ITCP, University of Crete, 70013 Heraklion, Greece
⁵⁴ INAF-Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius, Italy
⁵⁵ Physics and Astronomy Dept., University College London (UCL), London, UK
⁵⁶ The University of Tokyo, Department of Astronomy, Tokyo 113-0033, Japan
⁵⁷ Suwa University of Science, Chino, Nagano 391-0292, Japan
⁵⁸ INFN Sezione di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa, Italy
⁵⁹ Okayama University, Department of Physics, Okayama 700-8530, Japan
⁶⁰ Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France
⁶¹ National Institute of Technology, Kagawa College, 355 Chokushi-cho, Takamatsu, Kagawa 761-8058, Japan
⁶² Universitäts-Sternwarte, Fakultät für Physik, Ludwig-Maximilians Universität München, Scheinerstr.1, 81679 München, Germany
⁶³ NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA

Received: 15 February 2023
Accepted: 10 May 2023

Abstract

LiteBIRD is a planned JAXA-led cosmic microwave background (CMB) B-mode satellite experiment aiming for launch in the late 2020s, with a primary goal of detecting the imprint of primordial inflationary gravitational waves. Its current baseline focal-plane configuration includes 15 frequency bands between 40 and 402 GHz, fulfilling the mission requirements to detect the amplitude of gravitational waves with the total uncertainty on the tensor-to-scalar ratio, δr, down to δr < 0.001. A key aspect of this performance is accurate astrophysical component separation, and the ability to remove polarized thermal dust emission is particularly important. In this paper we note that the CMB frequency spectrum falls off nearly exponentially above 300 GHz relative to the thermal dust spectral energy distribution, and a relatively minor high frequency extension can therefore result in even lower uncertainties and better model reconstructions. Specifically, we compared the baseline design with five extended configurations, while varying the underlying dust modeling, in each of which the High-Frequency Telescope (HFT) frequency range was shifted logarithmically toward higher frequencies, with an upper cutoff ranging between 400 and 600 GHz. In each case, we measured the tensor-to-scalar ratio r uncertainty and bias using both parametric and minimum-variance component-separation algorithms. When the thermal dust sky model includes a spatially varying spectral index and temperature, we find that the statistical uncertainty on r after foreground cleaning may be reduced by as much as 30–50% by extending the upper limit of the frequency range from 400 to 600 GHz, with most of the improvement already gained at 500 GHz. We also note that a broader frequency range leads to higher residuals when fitting an incorrect dust model, but also it is easier to discriminate between models through higher χ² sensitivity. Even in the case in which the fitting procedure does not correspond to the underlying dust model in the sky, and when the highest frequency data cannot be modeled with sufficient fidelity and must be excluded from the analysis, the uncertainty on r increases by only about 5% for a 500 GHz configuration compared to the baseline.