From Galaxy to Intergalactic Medium -- the Magnetic Connection in the Age of the Square Kilometre Array

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I plan to detect and characterize `deep halos' of galaxies. These are gaseous halos, mainly consisting of cosmic rays and magnetic fields, that surround spiral galaxies.  The way to do this is to target galaxies that are edge-on to the line of sight.  When we look at such galaxies with the human eye, they look like a thin line in the sky because of their edge-on orientation.  Our eyes detect the optical light from stars in the galaxy and stars are mostly confined to a thin, spiral-like disk.  However, when we look at radio wavelengths, we start to see the faint halo emission that surrounds these disks. Radio halos extend so far from the the disk that edge-on galaxies no longer look like a thin line.  In fact, I have already shown (from stacking previous data) that most edge-on spiral galaxies look almost spherical when observed at radio wavelengths.  This is probably the case in the Milky Way as well, although it is harder to see this in our own Galaxy because of our location within it.  But if we could make such a measurement from the position of the Sun, we would likely find that the halo extent upwards(away from the plane where the Sun resides) is greater than the distance from the Sun to the Galactic Center! A deep halo is a halo that extends beyond even what I have described above (beyond about 10 kpc). We have every reason to expect that such halos exist because of our knowledge of magnetic fields and cosmic rays in and around galaxies, yet they have never before been detected.  Data that are already in hand as well as proposed new observations using the Very Large Array in New Mexico and the  MeerKat telescope in South Africa (a precursor to the Square Kilometre Array)  will achieve this goal.  Even halos that are closer in to the galaxy disk can yield their secrets through an analysis of the magnetic field strengths and cosmic ray energies.  Such analyses lead to a clear connection between disks and the intergalactic medium.  Halos and deep halos are similar to what we see around the Earth.  The Earth is surrounded by a magnetic field (the van Allen belts) that is constantly bombarded by cosmic rays from the Sun.  The fields adjust and distort in response to this Solar Wind, but remain intact nevertheless.  For galaxies, I am probing the galactic analog of the van Allen belts.  Sometimes, insights gained from looking at a large system from a bird's eye view can be applied to smaller local systems. Students involved in this process will receive scientific and technical expertise at a high level.  They will take part in `big data' science in an exciting project that pushes the boundaries of current knowledge. They will learn to do accurate image processing using many Tbytes of data.  My previous NSERC program led to four press releases in which Canada is featured internationally. The next step is likely to produce even more.