Origin and evolution of cosmic magnetism

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Observations show that magnetic fields are ubiquitous in the cosmos. Together with gravity, cosmic magnetic fields direct the flow of plasma and cosmic rays, and, indirectly, the motion of neutral gas. Still, we cannot answer basic questions about the structure of cosmic magnetic fields, the origin of large-scale magnetic fields in galaxies, and the properties of turbulence in magnetized plasma in space. Our lack of understanding of cosmic magnetic fields leaves major gaps in the physics of galaxy evolution, from the retention of hot gas and cosmic rays in the disk to support of cold molecular clouds against gravitational collapse. Galaxies represent the visible part of structure in the universe. It is here that stellar nucleosynthesis builds elements beyond hydrogen, helium and lithium. After nearly 14 billion years of evolution, all observable gas appears enriched by the products of stellar nucleosynthesis, even in intergalactic space. This fact bears testimony to the impact that the life cycle of stars on a galactic scale has on the evolution of galaxies and their wide environment. Some galaxies also host active galactic nuclei (AGN), that are powered by accretion of matter on a central, supermassive black hole. Beams of matter called jets are ejected at bulk relativistic speed, and form giant magnetic radio lobes in intergalactic space much larger than a galaxy. The ejection of matter, and its its associated kinetic energy and momentum, by stars and AGN is referred to as stellar feedback and AGN feedback. We cannot understand galaxy evolution without the physics of feedback. Magnetic fields play an important role in the physics of feedback, for example during various stages of star formation, acceleration and diffusion of cosmic rays, constraining galactic outflows, and collimating jets. In turn, stellar feedback provides energy for dynamo effects that amplify magnetic fields, while outflows and jets from AGN can inject magnetic fields into the intergalactic medium. Observations that reveal the structure an dynamical importance of magnetic fields provide crucial guidance for models of feedback and turbulence. This research program targets the complex feedback processes between gas and magnetic fields in galaxies, and their relation to the emergence of cosmic magnetic fields. In the next five years, we will lead by combining measurements of the velocity of plasma and neutral gas in the local interstellar medium with measurements of the magnetic field from the energy injection scale to the smallest observable turbulence. We will address the question of how magnetic fields evolved over cosmic time in spiral galaxies and in the lobes of radio galaxies the main sites for stellar and AGN feedback. My group excels in stacking, integrated polarization of galaxies, and statistics of rotation measures. We will lead application of these techniques toward our objectives through defined science projects proposed according to survey policies.