Detection of Cosmological 21cm Emission with CHIME

Intensity mapping of redshifted 21cm emission from neutral hydrogen holds great promise for learning about cosmology, as it provides an efficient way to map large volumes of the universe without the need to characterize individual luminous sources. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a cylinder telescope located in Western Canada that was custom-built for this purpose, and that has collected several hundred days' worth of data since it reached full observational capacity in late 2018. I will present the first 21cm science results from CHIME: the detection of a cross-correlation between CHIME sky maps and galaxy/quasar catalogs from the extended Baryon Oscillation Spectroscopic Survey (eBOSS). In particular, I will discuss our data processing pipeline and how we model the measured signal, as well as the implications and prospects for more precise future measurements.