Astrophysics and Cosmology with the Hydrogen Epoch of Reionization Array
Adrian Liu (Berkeley BCCP)
November 19, 2015
Abstract: In the next few years, the field of 21cm cosmology will provide qualitatively new insights into astrophysics and cosmology. Current and upcoming radio interferometer arrays will survey the distribution and ionization state of hydrogen at high redshifts (z ~ 6 to 13), providing the first direct observations of a thus far unexplored period in cosmic history. From the standpoint of astrophysics, this will enable precise constraints on cosmic dawn, when the first stars and galaxies formed and systematically ionized the intergalactic medium (IGM). In this talk, I will present the latest limits on the cosmological 21cm signal from the Precision Array for Probing the Epoch of Reionization (PAPER). These limits already place scientifically interesting constraints on the high-redshift IGM and suggest at least a minimal amount of X-ray heating from the first galaxies. I will then present forecasts of the expected performance of the recently commenced Hydrogen Epoch of Reionization Array (HERA), an instrument that promises to make high signal-to-noise characterizations of the cosmological 21cm signal. Such measurements should allow a detailed characterization of cosmic dawn, removing key uncertainties in other cosmological probes that arise from our currently poor understanding of the epoch. For example, I will discuss how 21cm measurements can in principle predict the optical depth to the Cosmic Microwave Background (CMB), enabling CMB uncertainties on the amplitude of primordial fluctuations to be reduced by a factor of four, and for a combination of HERA and Stage IV CMB experiments to measure the sum of the neutrino masses to 0.012eV.