The Simons Observatory: forecasted constraints on primordial gravitational waves with the expanded array of Small Aperture Telescopes
Cosmology and Nongalactic Astrophysics
2025-12-19 v1 High Energy Physics - Experiment
High Energy Physics - Theory
Abstract
We present updated forecasts for the scientific performance of the degree-scale (0.5 deg FWHM at 93 GHz), deep-field survey to be conducted by the Simons Observatory (SO). By 2027, the SO Small Aperture Telescope (SAT) complement will be doubled from three to six telescopes, including a doubling of the detector count in the 93 GHz and 145 GHz channels to 48,160 detectors. Combined with a planned extension of the survey duration to 2035, this expansion will significantly enhance SO's search for a -mode signal in the polarisation of the cosmic microwave background, a potential signature of gravitational waves produced in the very early Universe. Assuming a noise model with knee multipole and a moderately complex model for Galactic foregrounds, we forecast a (or 68% confidence level) constraint on the tensor-to-scalar ratio of , assuming no primordial -modes are present. This forecast assumes that 70% of the -mode lensing signal can ultimately be removed using high resolution observations from the SO Large Aperture Telescope (LAT) and overlapping large-scale structure surveys. For more optimistic assumptions regarding foregrounds and noise, and assuming the same level of delensing, this forecast constraint improves to . These forecasts represent a major improvement in SO's constraining power, being a factor of around 2.5 times better than what could be achieved with the originally planned campaign, which assumed the existing three SATs would conduct a five-year survey.
Keywords
Cite
@article{arxiv.2512.15833,
title = {The Simons Observatory: forecasted constraints on primordial gravitational waves with the expanded array of Small Aperture Telescopes},
author = {The Simons Observatory Collaboration and I. Abril-Cabezas and S. Adachi and P. Ade and A. E. Adler and P. Agrawal and J. Aguirre and S. Aiola and T. Alford and A. Ali and D. Alonso and M. A. Alvarez and R. An and M. Aravena and K. Arnold and P. Ashton and F. Astori and Z. Atkins and J. Austermann and S. Azzoni and C. Baccigalupi and D. Baker and R. Balafendiev and A. Baleato Lizancos and D. Barron and P. Barry and J. Bartlett and A. Basyrov and N. Battaglia and E. S. Battistelli and R. Battye and A. Bayer and A. Bazarko and J. A. Beall and R. Bean and D. Beck and S. Beckman and J. Begin and A. Beheshti and B. Beringue and T. Bhandarkar and S. Bhimani and F. Bianchini and E. Biermann and M. Billi and S. Biquard and B. Bixler and L. Bizzarri and S. Boada and D. Boettger and B. Bolliet and J. R. Bond and J. Borrill and J. Borrow and C. Braithwaite and T. L. R. Brien and M. L. Brown and S. M. Bruno and S. Bryan and R. Bustos and H. Cai and E. Calabrese and V. Calafut and F. M. Carl and A. Carones and J. Carron and A. Challinor and E. Chamberlain and P. Chanial and N. Chen and K. Cheung and B. Chiang and Y. Chinone and J. Chluba and H. S. Cho and S. K. Choi and M. Chu and J. Clancy and S. E. Clark and P. Clarke and J. Cleary and D. L. Clements and J. Connors and C. Contaldi and G. Coppi and L. Corbett and N. F. Cothard and W. Coulton and D. Crichton and K. D. Crowley and K. T. Crowley and A. Cukierman and J. M. D'Ewart and K. Dachlythra and O. Darwish and R. Datta and S. Day-Weiss and T. de Haan and S. Desai and M. Devlin and L. Di Mascolo and S. Dicker and K. Ding and C. Doux and P. Dow and S. Doyle and C. J. Duell and S. M. Duff and A. J. Duivenvoorden and J. Dunkley and M. Duparc and D. Dutcher and R. Dünner and M. Edenton and H. El Bouhargani and C. Embil Villagra and J. Errard and G. Fabbian and V. Fanfani and F. Farhadi Khouzani and G. S. Farren and J. Fergusson and S. Ferraro and R. Flauger and M. Forconi and A. Foster and K. Freese and J. C. Frisch and A. Frolov and G. Fuller and N. Galitzki and P. A. Gallardo and G. Galloni and J. T. Galvez Ghersi and K. Ganga and X. Garrido and E. Gawiser and M. Gerbino and R. Gerras and S. Giardiello and A. Gill and V. Gilles and U. Giri and E. Gleave and V. Gluscevic and N. Goeckner-Wald and S. Goldstein and J. E. Golec and S. Gordon and M. Gralla and S. Gratton and D. Green and J. C. Groh and C. Groppi and S. Grubb and Y. Guan and N. Gupta and J. E. Guðmundsson and B. Hadzhiyska and S. Hagstotz and P. Hargrave and S. Haridas and K. Harrington and I. Harrison and M. Hasegawa and M. Hasselfield and V. Haynes and M. Hazumi and A. He and E. Healy and S. W. Henderson and B. S. Hensley and E. Hertig and C. Hervías-Caimapo and M. Higuchi and C. A. Hill and J. C. Hill and M. Hilton and A. D. Hincks and G. Hinshaw and R. Hložek and A. Y. Q. Ho and S. Ho and S. P. Ho and T. D. Hoang and J. Hoh and J. Holder and J. Hood and E. Hornecker and A. L. Hornsby and S. C. Hotinli and Z. Huang and Z. B. Huber and J. Hubmayr and K. Huffenberger and A. Hughes and J. P. Hughes and A. Idicherian Lonappan and M. Ikape and K. Inaba and K. Irwin and J. Iuliano and A. H. Jaffe and B. Jain and D. Jain and H. T. Jense and O. Jeong and A. Johnson and B. R. Johnson and M. Johnson and M. E. Jones and N. Joshi and B. Jost and W. Kabalan and V. Kabra and D. Kaneko and J. Kania and E. D. Karpel and Y. Kasai and N. Katayama and B. Keating and B. Keller and R. Keskitalo and A. A. Khatua and J. Kim and T. Kisner and K. Kiuchi and K. Knowles and A. M. Kofman and Y. Koizumi and B. J. Koopman and A. Kosowsky and R. Kou and N. Krachmalnicoff and D. Kramer and A. Krishak and A. Krolewski and A. Kusaka and A. Kusiak and Y. Kvasiuk and P. La Plante and A. La Posta and A. Laguë and A. Lai and J. Lashner and M. Lattanzi and A. Lee and E. Lee and J. Leech and L. Legrand and C. Lessler and J. S. Leung and A. Lewis and Y. Li and Z. Li and M. Limon and L. Lin and E. Linder and M. Link and J. Liu and Y. Liu and J. Lloyd and J. Lonergan and T. Louis and T. Lucas and M. Ludlam and M. Lungu and M. Lyons and N. MacCrann and A. MacInnis and M. Madhavacheril and D. Mak and F. Maldonado and M. Mallaby-Kay and A. Manduca and A. Mangu and H. Mani and A. S. Maniyar and G. A. Marques and P. Masson and J. Mates and J. Mathewson and T. Matsumura and P. Mauskopf and A. May and N. McCallum and H. McCarrick and F. McCarthy and M. McCulloch and J. McMahon and P. D. Meerburg and Y. Mehta and J. Melin and E. Meulbroek and J. Meyers and A. Middleton and Y. Miki and A. Miller and M. Mirmelstein and Y. Mizozoe and B. Mohammadian and G. Montefalcone and K. Moodley and J. Moore and T. Morris and M. Morshed and T. Morton and E. Moser and T. Mroczkowski and M. Murata and J. Myers and M. Münchmeyer and S. Naess and H. Nakata and T. Namikawa and M. Nashimoto and F. Nati and P. Natoli and M. Negrello and S. K. Nerval and L. Newburgh and D. V. Nguyen and A. Nicola and M. D. Niemack and H. Nishino and Y. Nishinomiya and A. Novelli and S. O'Neill and N. Okumoto and A. Orlando and J. Orlowski-Scherer and L. Pagano and L. A. Page and S. Pandey and A. Papageorgiou and I. Paraskevakos and B. Partridge and D. Patel and R. Patki and S. Paulino Korte and M. Peel and K. Perez Sarmiento and F. Perrotta and P. Phakathi and L. Piccirillo and E. Pierpaoli and T. Pinsonneault-Marotte and G. Pisano and J. Pitocco and D. Poletti and C. Popik and B. Prasad and R. Puddu and G. Puglisi and F. J. Qu and F. Rahman and M. J. Randall and C. Ranucci and C. Raum and R. Reeves and C. L. Reichardt and M. Remazeilles and X. Ren and Y. Rephaeli and D. Riechers and B. Reid Guachalla and A. Rizzieri and J. Robe and M. F. Robertson and N. Robertson and K. Rogers and F. Rojas and A. Romero and E. Rosenberg and A. Rotti and S. Rowe and A. Roy and S. Sadeh and N. Sailer and K. Sakaguri and T. Sakuma and Y. Sakurai and M. Salatino and G. H. Sanders and D. Sasaki and M. Sathyanarayana Rao and T. P. Satterthwaite and L. Saunders and L. Scalcinati and E. Schaan and B. Schmitt and M. Schmittfull and N. Sehgal and J. Seibert and Y. Seino and U. Seljak and S. Shaikh and E. Shaw and P. Shellard and B. Sherwin and M. Shimon and J. E. Shroyer and C. Sierra and J. Sievers and C. Sifón and P. Sikhosana and M. Silva-Feaver and S. M. Simon and A. Sinclair and K. Smith and W. Sohn and X. Song and R. F. Sonka and T. Souverin and J. Spisak and S. T. Staggs and G. Stein and J. R. Stevens and R. Stompor and E. Storer and R. Sudiwala and Y. Sueno and J. Sugiyama and P. Suman and K. M. Surrao and S. Sutariya and A. Suzuki and J. Suzuki and O. Tajima and R. Takaku and S. Takakura and A. Takeuchi and I. Tansieri and A. C. Taylor and G. Teply and T. Terasaki and A. Thomas and D. B. Thomas and R. Thornton and P. Timbie and H. Trac and T. Tsan and E. Tsang King Sang and C. Tucker and J. Ullom and L. Vacher and L. Vale and A. van Engelen and J. Van Lanen and J. van Marrewijk and D. D. Van Winkle and C. Vargas and E. M. Vavagiakis and I. Veenendaal and C. Vergès and A. Villarrubia Aguilar and M. Vissers and M. Viña and K. Wagoner and S. Walker and L. Walters and Y. Wang and B. Westbrook and J. Williams and P. Williams and J. Wilson and H. Winch and E. J. Wollack and K. Wolz and J. Wong and Z. Xu and K. Yamada and E. Young and B. Yu and C. Yu and G. Zagatti and M. Zannoni and W. Zhang and K. Zheng and N. Zhu and A. Zonca and I. Zubeldia},
journal= {arXiv preprint arXiv:2512.15833},
year = {2025}
}
Comments
15 pages (excluding front matter), 4 figures, for submission to JCAP