Department of Physics, Engineering Physics & Astronomy

Queen's University
Search Type
Department of Physics, Engineering Physics & Astronomy
Department of Physics, Engineering Physics & Astronomy

CHIME: 21 cm and the Expanding Universe

Dr. Keith Vanderline
Dunlap Institute and Department of Astronomy & Astrophysics at the University of Toronto

Fri, Oct. 25, 2013
1:30 PM @ Stirling A


The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is an ambitious new project designed to map the distribution of matter in the Universe, over half the sky and a broad swath of cosmic history.

The newly-developed technique of Hydrogen Intensity (HI) mapping uses redshifted 21cm emission from neutral hydrogen as a 3D tracer of Large Scale Structure (LSS) in the Universe. Imprinted in the LSS is a remnant of the acoustic waves which propagated through the primordial plasma. This feature, the Baryon Acoustic Oscillation (BAO), manifests as a preferential separation scale between matter, and by charting the evolution of this scale over cosmic time, we can deduce the expansion history of the Universe.

Leveraging recent developments from from the cell phone industry (cheap, low noise amplifiers) and the huge growth in digital processing power, CHIME will be a highly efficient digital radio telescope, a many-antenna physically-fixed structure where beams are formed and pointed through digital processing rather than with physically steered dishes or cable delays. CHIME is composed of five 20m x 100m parabolic reflectors which focus radiation in one direction (east-west), while interferometry is used to resolve beams in the other (north-south), and earth rotation is used to sweep them across the sky.

I will discuss the motivation, design, and progress on both the full CHIME instrument and the 1/10th-scale Pathfinder which is currently under construction.