The Simons Observatory: Galactic Science Goals and Forecasts

Brandon S. Hensley, Susan E. Clark, Valentina Fanfani, Nicoletta Krachmalnicoff, Giulio Fabbian, Davide Poletti, Giuseppe Puglisi, Gabriele Coppi, Jacob Nibauer, Roman Gerasimov, Nicholas Galitzki, Steve K. Choi, Peter C. Ashton, Carlo Baccigalupi, Eric Baxter, Blakesley Burkhart, Erminia Calabrese, Jens Chluba, Josquin Errard, Andrei V. FrolovCarlos Hervías-Caimapo, Kevin M. Huffenberger, Bradley R. Johnson, Baptiste Jost, Brian Keating, Heather McCarrick, Federico Nati, Mayuri Sathyanarayana Rao, Alexander Van Engelen, Samantha Walker, Kevin Wolz, Zhilei Xu, Ningfeng Zhu, Andrea Zonca

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11 Scopus citations


Observing in six frequency bands from 27 to 280 GHz over a large sky area, the Simons Observatory (SO) is poised to address many questions in Galactic astrophysics in addition to its principal cosmological goals. In this work, we provide quantitative forecasts on astrophysical parameters of interest for a range of Galactic science cases. We find that SO can: constrain the frequency spectrum of polarized dust emission at a level of Δβ d ≲ 0.01 and thus test models of dust composition that predict that β d in polarization differs from that measured in total intensity; measure the correlation coefficient between polarized dust and synchrotron emission with a factor of two greater precision than current constraints; exclude the nonexistence of exo-Oort clouds at roughly 2.9σ if the true fraction is similar to the detection rate of giant planets; map more than 850 molecular clouds with at least 50 independent polarization measurements at 1 pc resolution; detect or place upper limits on the polarization fractions of CO(2-1) emission and anomalous microwave emission at the 0.1% level in select regions; and measure the correlation coefficient between optical starlight polarization and microwave polarized dust emission in 1° patches for all lines of sight with N H ≳ 2 × 1020 cm-2. The goals and forecasts outlined here provide a roadmap for other microwave polarization experiments to expand their scientific scope via Milky Way astrophysics.3737 A supplement describing author contributions to this paper can be found at

Original languageEnglish (US)
Article number166
JournalAstrophysical Journal
Issue number2
StatePublished - Apr 1 2022

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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