article · Journal of Cosmology and Astroparticle Physics
This research presents new power spectra of the cosmic microwave background (CMB) anisotropy in temperature and polarisation, derived from Data Release 6 maps from the Atacama Cosmology Telescope (ACT). These measurements cover 19,000 square degrees of sky and achieve white noise levels in polarisation three times lower than previous Planck data. The ACT angular power spectra are well-fitted by a sum of CMB and foregrounds, consistent with the ΛCDM cosmological model. By combining ACT data with larger-scale Planck data, WMAP data, CMB lensing, and baryon acoustic oscillation data from DESI, precise measurements of key cosmological parameters were obtained. The findings show no evidence for excess lensing or departure from spatial flatness, and detect Sunyaev-Zel'dovich anisotropy.
Accurately measuring cosmological parameters like the Hubble constant and the densities of different types of matter is crucial for understanding the universe's composition, expansion history, and fundamental physics. This research refines our knowledge of these parameters, contributing to a more precise and robust model of the cosmos.
The abstract does not indicate an application pathway for this fundamental research in cosmology.
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Abstract We present power spectra of the cosmic microwave background (CMB) anisotropy in temperature and polarization, measured from the Data Release 6 maps made from Atacama Cosmology Telescope (ACT) data. These cover 19,000 deg 2 of sky in bands centered at 98, 150 and 220 GHz, with white noise levels three times lower than Planck in polarization. We find that the ACT angular power spectra estimated over 10,000 deg 2 , and measured to arcminute scales in TT, TE and EE, are well fit by the sum of CMB and foregrounds, where the CMB spectra are described by the ΛCDM model. Combining ACT with larger-scale Planck data, the joint P-ACT dataset provides tight limits on the ingredients, expansion rate, and initial conditions of the universe. We find similar constraining power, and consistent results, from either the Planck power spectra or from ACT combined with WMAP data, as well as from either temperature or polarization in the joint P-ACT dataset. When combined with CMB lensing from ACT and Planck , and baryon acoustic oscillation data from the Dark Energy Spectroscopic Instrument (DESI DR1), we measure a baryon density of Ω b h 2 = 0.0226 ± 0.0001, a cold dark matter density of Ω c h 2 = 0.118 ± 0.001, a Hubble constant of H 0 = 68.22 ± 0.36 km/s/Mpc, a spectral index of n s = 0.974 ± 0.003, and an amplitude of density fluctuations of σ 8 = 0.813 ± 0.005. Including the DESI DR2 data tightens the Hubble constant to H 0 = 68.43 ± 0.27 km/s/Mpc; ΛCDM parameters agree between the P-ACT and DESI DR2 data at the 1.6 σ level. We find no evidence for excess lensing in the power spectrum, and no departure from spatial flatness. The contribution from Sunyaev-Zel'dovich (SZ) anisotropy is detected at high significance; we find evidence for a tilt with suppressed small-scale power compared to our baseline SZ template spectrum, consistent with hydrodynamical simulations with feedback.
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DOI: 10.1088/1475-7516/2025/11/062
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