Abstract

Intensity mapping of redshifted 21cm emission from neutral hydrogen holds vast promise for learning about cosmology, as it provides an efficient way to map large volumes of the universe without the need to characterize individual objects. In the first part of the talk, I will present the concept for the Packed Ultra-wideband Mapping Array (PUMA), a proposed next-generation experiment capable of performing intensity mapping over large sky areas up to redshift 6. I will review the primary scientific drivers for such an experiment, and highlight some secondary applications, including weak gravitational lensing of 21cm fluctuations and wave-optical effects in microlensing of radio sources. In the second part of the talk, I will provide an update on the status of the Canadian Hydrogen Intensity Mapping Experiment (CHIME), focusing on the outstanding challenges to extracting cosmological results and the methods being pursued to overcome these challenges.