Probing the Magnetic Field of the Milky Way with CHIME

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CHIME, one of the largest radio telescopes in the world, is now being built in Canada by three Canadian universities, UBC, Toronto, and McGill, at the Dominion Radio Astrophysical Observatory (DRAO) near Penticton, British Columbia. CHIME will look back in time to an earlier epoch of our Universe, to a time when Dark Energy began to influence the expansion. By charting the distribution of matter in galaxies CHIME will trace out four billion years in the history of the Universe. A second major task for CHIME is to search for Fast Radio Bursts, mysterious flashes of radio light that last only thousandths of a second and come from very far away. They seem to be tracers of very high-energy events, perhaps explosions, far beyond our Milky Way. CHIME will carry out these tasks simultaneously, with two computer signal processors analyzing the same stream of data. This proposal adds a third scientific stream - the study of the Milky Way galaxy in which we live. CHIME will receive radio energy from the Milky Way galaxy every moment of every day. The local signals are almost a nuisance for CHIME's first two purposes, but there is no way to switch them off or to eliminate them from the data stream. The funds awarded here will be used to support graduate students, pursuing Masters degrees and Doctorates, who will analyze the Milky Way signal looking for a description of the magnetic field between the stars of the Milky Way. The Milky Way is a galaxy, comprised of 100 billion stars, our Sun just a middle-of-the-road member of this ensemble. Thanks to radio astronomy, the space between the stars, once thought to be nearly empty, is known to be home to a tenuous but complex medium of gas, in atomic and molecular form, which has very cold regions intermingled with very hot regions. Mixed in is a dust of microscopic particles, the debris of dead stars. The whole is threaded by magnetic energy: magnetic field, just one millionth of the field that swings compass needles here on Earth, plays a significant role in the never-ending cycle of star birth and star death. Stars form from the interstellar material, and, late in their lives, return radiation and matter to it. The interstellar magnetic field, weak as it is, plays a big role in all these processes. Data from CHIME will join data from other large radio telescopes around the world in a quest to map interstellar magnetic fields and to understand their role in the "ecosystem" of the Milky Way.