Abstract: | We present new arcminute-resolution maps of the Cosmic Microwave Background
temperature and polarization anisotropy from the Atacama Cosmology Telescope,
using data taken from 2013-2016 at 98 and 150 GHz. The maps cover more than
17,000 deg$^2$, the deepest 600 deg$^2$ with noise levels below $10$
$mu$K-arcmin. We use the power spectrum derived from almost 6,000 deg$^2$ of
these maps to constrain cosmology. The ACT data enable a measurement of the
angular scale of features in both the divergence-like polarization and the
temperature anisotropy, tracing both the velocity and density at
last-scattering. From these one can derive the distance to the last-scattering
surface and thus infer the local expansion rate, $H_0$. By combining ACT data
with large-scale information from WMAP we measure $H_0=67.6pm 1.1$ km/s/Mpc,
at 68% confidence, in excellent agreement with the independently-measured
Planck satellite estimate (from ACT alone we find $H_0=67.9pm 1.5$ km/s/Mpc).
The $Lambda$CDM model provides a good fit to the ACT data, and we find no
evidence for deviations: both the spatial curvature, and the departure from the
standard lensing signal in the spectrum, are zero to within 1$sigma$; the
number of relativistic species, the primordial Helium fraction, and the running
of the spectral index are consistent with $Lambda$CDM predictions to within
1.5-2$sigma$. We compare ACT, WMAP, and Planck at the parameter level and find
good consistency; we investigate how the constraints on the correlated spectral
index and baryon density parameters readjust when adding CMB large-scale
information that ACT does not measure. The DR4 products presented here will be
publicly released on the NASA Legacy Archive for Microwave Background Data
Analysis. |