Mapping the Universe at 21 cm
Mapping the intensity of the 21 cm emission line from neutral hydrogen (HI) is a promising technique for characterizing the 3D matter distribution over large volumes of the Universe and out to high redshifts. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a radio interferometer specifically designed for this purpose. CHIME recently reported the detection of 21 cm emission from large-scale structure between redshifts 0.8 and 1.4. This was achieved by stacking maps of the radio sky, constructed from 102 nights of CHIME data, on the angular and spectral locations of galaxies and quasars from the eBOSS clustering catalogs. In this talk, I will introduce the experiment and provide an overview of the detection. I will describe key aspects of both the data processing pipeline and the simulation pipeline used to model the stacked signal. I will discuss the implications of the detection. Finally, I will evaluate the prospects for using CHIME -- and it's successor, the Canadian Hydrogen Observatory and Radio-transient Detector (CHORD) -- to measure the power spectrum of 21 cm emission, identify the signature of baryon acoustic oscillations, and constrain dark energy.