Kavli Affiliate: Kent Irwin
| First 5 Authors: Thibaut Louis, Adrien La Posta, Zachary Atkins, Hidde T. Jense, Irene Abril-Cabezas
| Summary:
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 $Lambda$CDM 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 Y1), we measure a baryon density of $Omega_b
h^2=0.0226pm0.0001$, a cold dark matter density of $Omega_c
h^2=0.118pm0.001$, a Hubble constant of $H_0=68.22pm0.36$ km/s/Mpc, a
spectral index of $n_s=0.974pm0.003$, and an amplitude of density fluctuations
of $sigma_8=0.813pm0.005$. 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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