The Astrophysical Journal (Jan 2024)

The Atacama Cosmology Telescope: Cosmology from Cross-correlations of unWISE Galaxies and ACT DR6 CMB Lensing

  • Gerrit S. Farren,
  • Alex Krolewski,
  • Niall MacCrann,
  • Simone Ferraro,
  • Irene Abril-Cabezas,
  • Rui An,
  • Zachary Atkins,
  • Nicholas Battaglia,
  • J. Richard Bond,
  • Erminia Calabrese,
  • Steve K. Choi,
  • Omar Darwish,
  • Mark J. Devlin,
  • Adriaan J. Duivenvoorden,
  • Jo Dunkley,
  • J. Colin Hill,
  • Matt Hilton,
  • Kevin M. Huffenberger,
  • Joshua Kim,
  • Thibaut Louis,
  • Mathew S. Madhavacheril,
  • Gabriela A. Marques,
  • Jeff McMahon,
  • Kavilan Moodley,
  • Lyman A. Page,
  • Bruce Partridge,
  • Frank J. Qu,
  • Emmanuel Schaan,
  • Neelima Sehgal,
  • Blake D. Sherwin,
  • Cristóbal Sifón,
  • Suzanne T. Staggs,
  • Alexander Van Engelen,
  • Cristian Vargas,
  • Lukas Wenzl,
  • Martin White,
  • Edward J. Wollack

DOI
https://doi.org/10.3847/1538-4357/ad31a5
Journal volume & issue
Vol. 966, no. 2
p. 157

Abstract

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We present tomographic measurements of structure growth using cross-correlations of Atacama Cosmology Telescope (ACT) DR6 and Planck cosmic microwave background (CMB) lensing maps with the unWISE Blue and Green galaxy samples, which span the redshift ranges 0.2 ≲ z ≲ 1.1 and 0.3 ≲ z ≲ 1.8, respectively. We improve on prior unWISE cross-correlations not just by making use of the new, high-precision ACT DR6 lensing maps, but also by including additional spectroscopic data for redshift calibration and by analyzing our measurements with a more flexible theoretical model. We determine the amplitude of matter fluctuations at low redshifts ( z ≃ 0.2–1.6), finding ${S}_{8}\equiv {\sigma }_{8}{({{\rm{\Omega }}}_{m}/0.3)}^{0.5}=0.813\pm 0.021$ using the ACT cross-correlation alone and S _8 = 0.810 ± 0.015 with a combination of Planck and ACT cross-correlations; these measurements are fully consistent with the predictions from primary CMB measurements assuming standard structure growth. The addition of baryon acoustic oscillation data breaks the degeneracy between σ _8 and Ω _m , allowing us to measure σ _8 = 0.813 ± 0.020 from the cross-correlation of unWISE with ACT and σ _8 = 0.813 ± 0.015 from the combination of cross-correlations with ACT and Planck. These results also agree with the expectations from primary CMB extrapolations in ΛCDM cosmology; the consistency of σ _8 derived from our two redshift samples at z ∼ 0.6 and 1.1 provides a further check of our cosmological model. Our results suggest that structure formation on linear scales is well described by ΛCDM even down to low redshifts z ≲ 1.

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