The Atacama Cosmology Telescope: Two-Season ACTPol Spectra and Parameters

TL;DR

This paper presents new measurements of the cosmic microwave background's temperature and polarization spectra from the Atacama Cosmology Telescope, combining data from multiple years and instruments to refine cosmological parameters within the LCDM model.

Contribution

The study provides the first polarization spectra from ACTPol over two seasons and combines these with previous ACT and Planck data for improved cosmological constraints.

Findings

ACTPol data are consistent with LCDM.

Polarization spectra improve constraints on key cosmological parameters.

Adding ACTPol data reduces uncertainties on neutrino and helium parameters.

Abstract

We present the temperature and polarization angular power spectra measured by the Atacama Cosmology Telescope Polarimeter (ACTPol). We analyze night-time data collected during 2013-14 using two detector arrays at 149 GHz, from 548 deg$^2$ of sky on the celestial equator. We use these spectra, and the spectra measured with the MBAC camera on ACT from 2008-10, in combination with Planck and WMAP data to estimate cosmological parameters from the temperature, polarization, and temperature-polarization cross-correlations. We find the new ACTPol data to be consistent with the LCDM model. The ACTPol temperature-polarization cross-spectrum now provides stronger constraints on multiple parameters than the ACTPol temperature spectrum, including the baryon density, the acoustic peak angular scale, and the derived Hubble constant. Adding the new data to planck temperature data tightens the limits on damping tail parameters, for example reducing the joint uncertainty on the number of neutrino species and the primordial helium fraction by 20%.