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The Atacama Cosmology Telescope: A Measurement of the Cosmic Microwave Background Power Spectrum at 148 and 218 GHz from the 2008 Southern Survey

Sudeep Das, Tobias A. Marriage, Peter A. R. Ade, Paula Aguirre, Mandana Amir, John W. Appel, L. Felipe Barrientos, Elia S. Battistelli, J. Richard Bond, Ben Brown, Bryce Burger, Jay Chervenak, Mark J. Devlin, Simon R. Dicker, W. Bertrand Doriese, Joanna Dunkley, Rolando Dünner, Thomas Essinger-Hileman, Ryan P. Fisher, Joseph W. Fowler, Amir Hajian, Mark Halpern, Matthew Hasselfield, Carlos Hernández-Monteagudo, Gene C. Hilton, Matt Hilton, Adam D. Hincks, Renée Hlozek, Kevin M. Huffenberger, David H. Hughes, John P. Hughes, Leopoldo Infante, Kent D. Irwin, Jean Baptiste Juin, Madhuri Kaul, Jeff Klein, Arthur Kosowsky, Judy M Lau, Michele Limon, Yen-Ting Lin, Robert H. Lupton, Danica Marsden, Krista Martocci, Phil Mauskopf, Felipe Menanteau, Kavilan Moodley, Harvey Moseley, Calvin B. Netterfield, Michael D. Niemack, Michael R. Nolta, Lyman A. Page, Lucas Parker, Bruce Partridge, Beth Reid, Neelima Sehgal, Blake D. Sherwin, Jon Sievers, David N. Spergel, Suzanne T. Staggs, Daniel S. Swetz, Eric R. Switzer, Robert Thornton, Hy Trac, Carole Tucker, Ryan Warne, Ed Wollack, Yue Zhao

TL;DR

ACT measures the CMB power spectrum at 148 and 218 GHz from the 2008 Southern Survey, spanning $500<\ell<10{,}000$, and resolves the second through seventh acoustic peaks. The analysis uses four patches with four splits each, employing high-pass filtering, prewhitening, and exact mode-coupling corrections to produce unbiased, cross- and auto-spectra across multipoles. They detect gravitational lensing at $2.8\sigma$, constrain foregrounds such as dusty galaxies and SZ contributions, and reveal a faint Galactic dust signal, all while anchoring calibration to WMAP and Uranus. The results test ΛCDM with high-precision small-scale measurements and provide publicly releasable data for community use.

Abstract

We present measurements of the cosmic microwave background (CMB) power spectrum made by the Atacama Cosmology Telescope at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. Our results clearly show the second through the seventh acoustic peaks in the CMB power spectrum. The measurements of these higher-order peaks provide an additional test of the ΛCDM cosmological model. At l > 3000, we detect power in excess of the primary anisotropy spectrum of the CMB. At lower multipoles 500 < l < 3000, we find evidence for gravitational lensing of the CMB in the power spectrum at the 2.8σ level. We also detect a low level of Galactic dust in our maps, which demonstrates that we can recover known faint, diffuse signals.

The Atacama Cosmology Telescope: A Measurement of the Cosmic Microwave Background Power Spectrum at 148 and 218 GHz from the 2008 Southern Survey

TL;DR

ACT measures the CMB power spectrum at 148 and 218 GHz from the 2008 Southern Survey, spanning , and resolves the second through seventh acoustic peaks. The analysis uses four patches with four splits each, employing high-pass filtering, prewhitening, and exact mode-coupling corrections to produce unbiased, cross- and auto-spectra across multipoles. They detect gravitational lensing at , constrain foregrounds such as dusty galaxies and SZ contributions, and reveal a faint Galactic dust signal, all while anchoring calibration to WMAP and Uranus. The results test ΛCDM with high-precision small-scale measurements and provide publicly releasable data for community use.

Abstract

We present measurements of the cosmic microwave background (CMB) power spectrum made by the Atacama Cosmology Telescope at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. Our results clearly show the second through the seventh acoustic peaks in the CMB power spectrum. The measurements of these higher-order peaks provide an additional test of the ΛCDM cosmological model. At l > 3000, we detect power in excess of the primary anisotropy spectrum of the CMB. At lower multipoles 500 < l < 3000, we find evidence for gravitational lensing of the CMB in the power spectrum at the 2.8σ level. We also detect a low level of Galactic dust in our maps, which demonstrates that we can recover known faint, diffuse signals.

Paper Structure

This paper contains 18 sections, 39 equations, 13 figures, 1 table.

Table of Contents

  1. INTRODUCTION
  2. OBSERVATIONS AND MAPMAKING
  3. Mapmaking
  4. Beam Measurements
  5. Calibration
  6. POWER SPECTRUM METHOD
  7. Fields used for Spectra
  8. Preprocessing of Maps
  9. The Data Window
  10. Azimuthal Fourier-mode Weights and Binning
  11. Mode-coupling
  12. Summary of power spectrum method
  13. SIMULATIONS
  14. POWER SPECTRUM
  15. FOREGROUNDS
  16. ...and 3 more sections

Figures (13)

  • Figure 1: The rms temperature uncertainty for one-arcminute pixels for the 148 GHz maps (top) and 218 GHz map (bottom). Also shown in bold lines are the boundaries of the four rectangular patches used for spectral analysis.
  • Figure 2: Beam deconvolved noise power spectra of the 148 GHz (open circles) and the 218 GHz (filled circles) maps shown against a theoretical lensed CMB spectrum (solid line). The theoretical white noise levels are shown using dashed (for 148 GHz) and dotted (for 218 GHz) lines.
  • Figure 3: Azimuthal weights used for binning the $148\times 148$ GHz spectrum. The horizontal stripe is an artifact of the symmetry of the Fourier space, and does not affect our calculations. The vertical stripe of zero weight is added in by hand, as described in the text. Due to the symmetry of Fourier transforms, only the upper half plane of this weight map is independent. The small grainy disk at the center corresponds to $\ell<500$ where we do not perform any smoothing --- these modes are discarded from the final power spectrum.
  • Figure 4: Anisotropic noise in data and simulated patches. Top: Difference map of two splits in an 148 GHz data patch (left), and its 2D power spectrum (right). Bottom: Same as above, except for a simulated patch. This random realization was seeded by the noise power spectrum of data patch shown in the top panel, as described in the text.
  • Figure 5: Normalized covariance matrix for decorrelated bandpowers for 148 GHz $\times$ 148 GHz spectrum, based on 960 signal+noise Monte Carlo simulations. The bins are defined in Table \ref{['tab: spec_table']}. All values on the diagonal are unity by definition. The colorbar has been stretched to reveal the variations in the off-diagonal elements.
  • ...and 8 more figures