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The Atacama Cosmology Telescope: Cosmological parameters from three seasons of data

Jonathan L. Sievers, Renée A. Hlozek, Michael R. Nolta, Viviana Acquaviva, Graeme E. Addison, Peter A. R. Ade, Paula Aguirre, Mandana Amiri, John William Appel, L. Felipe Barrientos, Elia S. Battistelli, Nick Battaglia, J. Richard Bond, Ben Brown, Bryce Burger, Erminia Calabrese, Jay Chervenak, Devin Crichton, Sudeep Das, Mark J. Devlin, Simon R. Dicker, W. Bertrand Doriese, Joanna Dunkley, Rolando Dünner, Thomas Essinger-Hileman, David Faber, Ryan P. Fisher, Joseph W. Fowler, Patricio Gallardo, Michael S. Gordon, Megan B. Gralla, Amir Hajian, Mark Halpern, Matthew Hasselfield, Carlos Hernández-Monteagudo, J. Colin Hill, Gene C. Hilton, Matt Hilton, Adam D. Hincks, Dave Holtz, Kevin M. Huffenberger, David H. Hughes, John P. Hughes, Leopoldo Infante, Kent D. Irwin, David R. Jacobson, Brittany Johnstone, Jean Baptiste Juin, Madhuri Kaul, Jeff Klein, Arthur Kosowsky, Judy M Lau, Michele Limon, Yen-Ting Lin, Thibaut Louis, Robert H. Lupton, Tobias A. Marriage, Danica Marsden, Krista Martocci, Phil Mauskopf, Michael McLaren, Felipe Menanteau, Kavilan Moodley, Harvey Moseley, Calvin B Netterfield, Michael D. Niemack, Lyman A. Page, William A. Page, Lucas Parker, Bruce Partridge, Reed Plimpton, Hernan Quintana, Erik D. Reese, Beth Reid, Felipe Rojas, Neelima Sehgal, Blake D. Sherwin, Benjamin L. Schmitt, David N. Spergel, Suzanne T. Staggs, Omelan Stryzak, Daniel S. Swetz, Eric R. Switzer, Robert Thornton, Hy Trac, Carole Tucker, Masao Uehara, Katerina Visnjic, Ryan Warne, Grant Wilson, Ed Wollack, Yue Zhao, Caroline Zunckel

TL;DR

The paper analyzes three years of ACT data at 148 and 218 GHz to jointly constrain cosmological parameters and microwave foregrounds, incorporating SZ effects, CIB, point sources, and lensing deflection with WMAP7 data. Using a sophisticated multi-frequency likelihood and MCMC, it finds overall agreement with ΛCDM, places tight bounds on N_eff and Σm_ν, and limits on tensor modes, early dark energy, and α variation. It also measures SZ amplitudes and constrains tSZ-CIB correlations, with lensing amplitudes broadly consistent with predictions. The results reinforce the standard cosmological model while tightening constraints on extensions, and demonstrate ACT’s power in separating primary CMB from secondary signals on small angular scales.

Abstract

We present constraints on cosmological and astrophysical parameters from high-resolution microwave background maps at 148 GHz and 218 GHz made by the Atacama Cosmology Telescope (ACT) in three seasons of observations from 2008 to 2010. A model of primary cosmological and secondary foreground parameters is fit to the map power spectra and lensing deflection power spectrum, including contributions from both the thermal Sunyaev-Zeldovich (tSZ) effect and the kinematic Sunyaev-Zeldovich (kSZ) effect, Poisson and correlated anisotropy from unresolved infrared sources, radio sources, and the correlation between the tSZ effect and infrared sources. The power ell^2 C_ell/2pi of the thermal SZ power spectrum at 148 GHz is measured to be 3.4 +\- 1.4 muK^2 at ell=3000, while the corresponding amplitude of the kinematic SZ power spectrum has a 95% confidence level upper limit of 8.6 muK^2. Combining ACT power spectra with the WMAP 7-year temperature and polarization power spectra, we find excellent consistency with the LCDM model. We constrain the number of effective relativistic degrees of freedom in the early universe to be Neff=2.79 +\- 0.56, in agreement with the canonical value of Neff=3.046 for three massless neutrinos. We constrain the sum of the neutrino masses to be Sigma m_nu < 0.39 eV at 95% confidence when combining ACT and WMAP 7-year data with BAO and Hubble constant measurements. We constrain the amount of primordial helium to be Yp = 0.225 +\- 0.034, and measure no variation in the fine structure constant alpha since recombination, with alpha/alpha0 = 1.004 +/- 0.005. We also find no evidence for any running of the scalar spectral index, dns/dlnk = -0.004 +\- 0.012.

The Atacama Cosmology Telescope: Cosmological parameters from three seasons of data

TL;DR

The paper analyzes three years of ACT data at 148 and 218 GHz to jointly constrain cosmological parameters and microwave foregrounds, incorporating SZ effects, CIB, point sources, and lensing deflection with WMAP7 data. Using a sophisticated multi-frequency likelihood and MCMC, it finds overall agreement with ΛCDM, places tight bounds on N_eff and Σm_ν, and limits on tensor modes, early dark energy, and α variation. It also measures SZ amplitudes and constrains tSZ-CIB correlations, with lensing amplitudes broadly consistent with predictions. The results reinforce the standard cosmological model while tightening constraints on extensions, and demonstrate ACT’s power in separating primary CMB from secondary signals on small angular scales.

Abstract

We present constraints on cosmological and astrophysical parameters from high-resolution microwave background maps at 148 GHz and 218 GHz made by the Atacama Cosmology Telescope (ACT) in three seasons of observations from 2008 to 2010. A model of primary cosmological and secondary foreground parameters is fit to the map power spectra and lensing deflection power spectrum, including contributions from both the thermal Sunyaev-Zeldovich (tSZ) effect and the kinematic Sunyaev-Zeldovich (kSZ) effect, Poisson and correlated anisotropy from unresolved infrared sources, radio sources, and the correlation between the tSZ effect and infrared sources. The power ell^2 C_ell/2pi of the thermal SZ power spectrum at 148 GHz is measured to be 3.4 +\- 1.4 muK^2 at ell=3000, while the corresponding amplitude of the kinematic SZ power spectrum has a 95% confidence level upper limit of 8.6 muK^2. Combining ACT power spectra with the WMAP 7-year temperature and polarization power spectra, we find excellent consistency with the LCDM model. We constrain the number of effective relativistic degrees of freedom in the early universe to be Neff=2.79 +\- 0.56, in agreement with the canonical value of Neff=3.046 for three massless neutrinos. We constrain the sum of the neutrino masses to be Sigma m_nu < 0.39 eV at 95% confidence when combining ACT and WMAP 7-year data with BAO and Hubble constant measurements. We constrain the amount of primordial helium to be Yp = 0.225 +\- 0.034, and measure no variation in the fine structure constant alpha since recombination, with alpha/alpha0 = 1.004 +/- 0.005. We also find no evidence for any running of the scalar spectral index, dns/dlnk = -0.004 +\- 0.012.

Paper Structure

This paper contains 31 sections, 41 equations, 22 figures, 6 tables.

Table of Contents

  1. Introduction
  2. Data
  3. Beam and calibration errors
  4. Additional data
  5. Methodology
  6. Constraints on primordial parameters
  7. ACT data alone
  8. Effective number of relativistic species
  9. Massive neutrinos
  10. Early dark energy
  11. Inflationary parameters
  12. The scalar spectral index
  13. $\Lambda$CDM + Running Index
  14. $\Lambda$CDM+Tensor modes
  15. Curvature
  16. ...and 16 more sections

Figures (22)

  • Figure 1: Data used in this cosmological analysis. The data from the WMAP 7-year data release larson/etal:2011komatsu/etal:2011 are combined with the ACT data. In this figure we show a weighted co-added spectrum from the equatorial and southern patches at 148 GHz. The full ACT likelihood, however, considers independent southern and equatorial spectra for both 148 GHz and 218 GHz das/etal:2012prep and their cross-frequency spectrum, which are shown in Figure \ref{['fig:multispec']}. The solid line indicates the best-fit cosmological model including foreground emission, while the dashed line shows the best-fit primordial CMB spectrum. This binning was selected for the common analysis of the equatorial and southern data. See das/etal:2012prep for alternative binnings.
  • Figure 2: The ACT multi-frequency data. Each solid line indicates the best-fit total model for each cross spectrum, while the dashed lines show the radio power; the dot-dashed line indicates the power from CIB sources (both Poisson and correlated CIB); the gray lines show the total SZ power. The solid and dotted gray lines are for those spectra including 218 GHz and consist of only the kSZ contribution, while the dashed gray line is for the 148x148 GHz spectrum. The dotted lines show the (negative of) the (SZ-CIB) correlation. In all cases the models are for the best fit in a $\Lambda$CDM scenario.
  • Figure 3: Parameter constraints on the $\Lambda$CDM model for the combined ACT and WMAP 7-year power spectra. For each parameter, the full likelihood is marginalized over the other parameters. Dotted curves for the primary parameters are for WMAP7 data only. The solid curves are for ACT plus WMAP7, and the dashed lines add priors from measurements of the baryon acoustic peak anderson/etal:2012percival/etal:2009beutler/etal:2011 and a direct measurement of $H_0$riess/etal:2011. The constraints are summarized in Tables \ref{['table:wa_damp_params']},\ref{['table:wa_params']} and \ref{['table:wabh_params']}. Since the $\xi$ parameter is unconstrained and set only by the prior, $0< \xi < 0.2,$ it is not shown in the tables.
  • Figure 4: Constraints on the $\Lambda$CDM cosmological model using the likelihood of marginalized CMB bandpowers using ACT+ACTDefl data, compared to the constraints from ACT+ACTDefl+WMAP7, where ACTDefl is the reconstructed deflection power spectrum from ACT data, and WMAP7 alone. The top six panels are fitted parameters, while the bottom two rows are derived parameters. For the ACT-only parameters, two cases are shown: one where we fix the optical depth $\tau$, and another where the scalar spectral index $n_s$ is fixed. Fixing $n_s$ tightens the constraint on the amplitude of scalar perturbations (the ACT+ACTDefl, $n_s$ fixed curve lies on the ACT+ACTDefl+WMAP7 curve), but does not cause significant shifts in the other primary parameters, relative to leaving $n_s$ free. The independent CMB data sets, ACT and WMAP7, are consistent with the $\Lambda$CDM model.
  • Figure 5: Marginalized one-dimensional likelihood of the $N_\mathrm{eff}$ for ACT data in combination with other probes. Left panel: The improvement in constraints of the ACT in combination with WMAP7 data relative to WMAP7 data on its own. Right panel: The $N_\mathrm{eff}$ likelihood for WMAP7+ACT data and a variety of other probes. The constraints are consistent with $N_\mathrm{eff} = 3.046$, the value in the model with three neutrino species. The slight shifts in the central value can be understood in the context of the changes in the value of the Hubble parameter, as illustrated in Figure \ref{['fig:neff_h0']}.
  • ...and 17 more figures