Grant: Discovery Grants Program - Individual

Modern astronomers use large telescopes to efficiently survey our universe and catalog millions of stars, galaxies, and accreting black holes known as quasars. For a glimpse of the understanding we can develop using these surveys, imagine voyaging out of our solar system and far beyond all the stars in our Milky Way galaxy. The faint dots of light that would be visible to you then then aren't stars, but entire distant galaxies. At the centre of any of those galaxies you'll find a swarm of stars and, if the galaxy is big enough, a black hole with a mass of millions or even billions of Suns. Imagine watching over centuries as one of the gas clouds of hydrogen, helium, and other elements in that galaxy ventures too close to the black hole. Gravity stretches the gas cloud into a disk of gas bigger than our solar system, orbiting at incredible speeds but slowly spiraling inwards to accrete onto the black hole. In the inner disk, friction makes the gas hotter than the Sun over an area millions of times larger than the Sun's surface. That enormous, glowing disk can be seen all the way across the universe, and we call it a quasar. This turbulent accretion disk of hot, rotating gas often tosses up gas clumps which are pushed outward by the light from the inner disk. The clumps form spiraling streamers of gas and dust which block the inner disk from view in some directions and which race out into the galaxy hosting the quasar. These fast-moving winds can reverse the inflow of gas clouds supplying the accretion disk, shutting down the accretion process and turning off the quasar. They can even shock-heat and blow out almost all the gas in the galaxy, ending star formation in it and drastically changing its future appearance and environment. Learning how quasars and their winds work refine our understanding of these fascinating objects and improves our models of how galaxies form and develop. My research team and collaborators and I study quasars that show signs of these winds. In the next 5 years, my research group and I will study quasars and their winds changing with time in the Sloan Digital Sky Survey Mark V, including hundreds of quasars with more repeat observations than ever previously obtained. We will test model predictions for how quasar winds are initially accelerated (and later decelerated) and how those winds may sweep up and accelerate preexisting gas clouds in the surrounding galaxy. We will determine if quasars that show gas apparently infalling at up to 5% of lightspeed are in fact rotating winds seen near their launching point. We will use advanced computing techniques to predict the true, dust-free spectra of individual quasars from observations of hundreds of thousands of quasars seen through varying amounts of dust. We will refine the relationship between a quasar's energy output and the size of its emission regions, enabling more accurate measurements of the masses of the black holes in quasars throughout the history of the universe.