Henry DeWolf Smyth Professsor of Physics
Suzanne Staggs is an experimentalist who makes measurements of the cosmic microwave background (CMB) radiation left over from the universal primeval plasma. (As the universe expanded and cooled, the photons eventually decoupled from the baryonic matter when their typical energies were insufficient to ionize hydrogen; at that point the universe became largely neutral and the photons passed through it without scattering.) The current experiments are of two types: measurements of the polarization of the CMB and of the CMB's very fine-scale features.
The experiments take advantage of the recent surge in innovative and sensitive detectors for microwave and millimeter radiation. The experimental CMB group includes Jo Dunkley, Norman Jarosik, Bill Jones, and Lyman Page, as well as some dozen graduate students and several postdocs. We have close ties to the theoretical cosmologists in the department (Paul Steinhardt and Frans Pretorius), and we also collaborate with many members of the astrophysics department (including associated faculty member David Spergel). Our experimental program is characterized by a nicely-balanced mix of very technical, cutting-edge hands-on work with detectors and optics, and design of experiments robust to the many subtle systematic effects possible in this work, combined with plenty of data analysis, using the many powerful statistical techniques now common to the field of CMB research.
The polarization of the CMB is only a few parts per billion. It arises from the fact that an unpolarized incident wave scattered from an electron emerges with an angle-dependent polarization; anisotropy in the radiation at the time of its last encounter with electrons results in a net polarization of the CMB. The majority of the polarization patterns emerge because of the anisotropy in the primordial plasma at the time of decoupling; this same anisotropy is probed exquisitely well by the present day maps of the CMB temperature by, for example, WMAP and PLANCK. However, gravitational waves permeating the universe can also present anisotropic scattering conditions and thus imprint polarization onto the CMB; in distinction to the those from the plasma anisotropies, these patterns can come in either global parity. Since gravitational waves could emerge from extremely early times, possibly from an epoch of inflation, detailed study of the polarization may provide information on the universe's first few atto-seconds! More information can be found in many places; including two review articles in the list below.
Measurement of the fine-scale features in the temperature of the CMB across the celestial sphere (at arcminute scales) probe the universe in new ways to the extant larger-angular-scale measurements. Those larger-angular-scale measurements paint a picture of the fundamental properties of our universe, including its baryon content, its dark matter content, its spatial geometry, and the fact that it is shot through with dark energy. Measurements at arcminute scales (fine scales) will provide further explanation of how the universe has evolved to its present day state, and will address questions about the properties of the neutrinos (including their summed masses) and the nature of dark energy and gravity itself.
Staggs is the PI of the Advanced ACTPol (AdvACT) project. This is the current generation of the Atacama Cosmology Telescope project, also known as ACT(link is external). Since ACT is a large telescope (6 m diameter), it can make maps of the fine-scale features in the CMB. Our group is intimately involved at all levels of the project, with a particular emphasis on the detector arrays for the camera. Staggs is also a founding member of the Simons Observatory (https://simonsobservatory.org/, SO), which is building a suite of instruments for measuring the CMB from large to small angular scales. Again our group is focused on camera development. For ACT, the new camera included three large arrays of two-color polarimeters based on transition edge sensor (TES) detectors. For SO, we are building 49 such polarimeter arrays. We used similar one-color devices in ABS. Additionally, the Staggs group has done work characterizing so-called multi-moded detectors which are a key component of the design of a satellite proposed by Goddard Space Flight Center, PIXIE, to get even more information out of the CMB with exquisitely sensitive measurements of the frequency dependence of the blackbody spectrum of the CMB.
- Recent discoveries from the cosmic microwave background; a review of recent progress. S. Staggs, J. Dunkley, and L. Page., Reports on Progress in Physics 81, 044901, 2018.
- The Atacama Cosmology Telescope: The Two-Season ACTPol Sunyaev-Zeldovich Effect Selected Cluster Catalog. M. Hilton, M. Hasselfield, C. Sifon, N. Battaglia, et al., APJ Supplement Series, 235, 20, 2018.
- Results from the Atacama B-mode Search (ABS) experiment. A. Kusaka, et al., Journal of Cosmology and Astro-Particle Physics, 2018, 005, 2018.
- The Atacama Cosmology Telescope; two season ACTPol spectra and parameters., T. Louis, E. Grace, M. Hasselfield, M. Lungu, L. Maurin et al., JCAP 6, 031, 2017.
- The Simons Observatory: Science goals and forecasts., The Simons Observatory Collaboration, arXiv: 1808.07445, 2018.
- The Cosmic Microwave Background for Pedestrians: A Review for Particle and Nuclear Physicists, Samtleben, D., Staggs, S. T., & B. Winstein, ARNPS, 57, p.245-283 astro-ph/0803.0834, 2007.
- Princeton Problems in Physics, with Solutions, Nathan Newbury, Michael Newman, John Ruhl, Suzanne Staggs, and Stephen Thorsett, Princeton University Press. (Monograph.), 1990.
- See also act.princeton.edu for more publications.