Nils Halverson

About

Nils Halverson develops millimeter-wavelength instrumentation to study the origins of the universe through observations of the Cosmic Microwave Background (CMB). His research focuses on using CMB observations to gather evidence for gravitational waves released by an early period of inflation, as well as constraining neutrino mass and understanding the growth of structure and dark energy. He is a co-investigator on two ground-based CMB experiments: the South Pole Telescope (SPT) and Polarbear/Simons Array. Additionally, he is a Co-Investigator on a NASA Technology Development Grant aimed at advancing focal plane technology for next-generation CMB space missions.

Research topics

• Physics
• Astronomy
• Astrophysics
• Optics
• Remote sensing
• Computer Science
• Particle physics
• Geology
• Geography
• Statistics

Selected publications

• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way

  The Astrophysical Journal Letters · 2022 · 1712 citations

  Abstract We present the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength of λ = 1.3 mm. The EHT data resolve a compact emission region with intrahour variability. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a d…

  DOI

• Measurements of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>E</mml:mi></mml:math>-mode polarization and temperature-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>E</mml:mi></mml:math>-mode correlation of the CMB from SPT-3G 2018 data

  Physical review. D/Physical review. D. · 2021 · 259 citations

  We present measurements of the $E$-mode ($EE$) polarization power spectrum and temperature-$E$-mode ($TE$) cross-power spectrum of the cosmic microwave background using data collected by SPT-3G, the latest instrument installed on the South Pole Telescope. This analysis uses observations of a $1500\text{ }\text{ }{\mathrm{deg}}^{2}$ region at 95, 150, and 220 GHz taken over a four-month period in 2018. We report binned values of the $EE$ and $TE$ power spectra over the angular multipole range $30…

  DOI

• CMB-S4: Forecasting Constraints on Primordial Gravitational Waves

  The Astrophysical Journal · 2022 · 256 citations

  Abstract CMB-S4—the next-generation ground-based cosmic microwave background (CMB) experiment—is set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the universe. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semianalytic proj…

  PublisherOA PDFDOI

• The SPTpol Extended Cluster Survey

  The Astrophysical Journal Supplement Series · 2020 · 200 citations

  Abstract We describe the observations and resultant galaxy cluster catalog from the 2770 deg 2 SPTpol Extended Cluster Survey (SPT-ECS). Clusters are identified via the Sunyaev–Zel’dovich (SZ) effect and confirmed with a combination of archival and targeted follow-up data, making particular use of data from the Dark Energy Survey (DES). With incomplete follow-up we have confirmed as clusters 244 of 266 candidates at a detection significance ξ ≥ 5 and an additional 204 systems at 4 &lt; ξ &lt; 5.…

  DOI

• Constraints on Cosmological Parameters from the 500 deg² SPTPOL Lensing Power Spectrum

  The Astrophysical Journal · 2020 · 87 citations

  Abstract We present cosmological constraints based on the cosmic microwave background (CMB) lensing potential power spectrum measurement from the recent 500 deg 2 SPTpol survey, the most precise CMB lensing measurement from the ground to date. We fit a flat ΛCDM model to the reconstructed lensing power spectrum alone and in addition with other data sets: baryon acoustic oscillations (BAO), as well as primary CMB spectra from Planck and SPTpol . The cosmological constraints based on SPTpol and Pl…

  DOI

Recent grants

• CAREER: Large focal plane array development for CMB polarization studies with the South Pole Telescope

  NSF · $875k · 2010–2016

Frequent coauthors

• M. Dobbs

  Canadian Institute for Advanced Research

  481 shared

• C. L. Chang

  Argonne National Laboratory

  467 shared

• B. A. Benson

  Netherlands Institute for Radio Astronomy

  462 shared

• J. E. Carlstrom

  405 shared

• S. S. Meyer

  388 shared

• L. E. Bleem

  University of Chicago

  368 shared

• W. L. Holzapfel

  359 shared

• K. K. Schaffer

  University of Chicago

  335 shared

Education

• PhD, Applied Physics

  California Institute of Technology

  2002

• MS, Applied Physics

  California Institute of Technology

  1993

• BS, Physics

  Stanford University

  1991

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