A Study of Gas Flows and Structure Formation in the Milky Way

Johns Hopkins University, Baltimore MD

Investigators

Abstract

Earth formed from dusty gas in space, circling a young sun. The sun formed from the core of a huge cloud of molecular gas in our galaxy. The investigators are studying how other solar systems form from hot gas cooling into dense, dark clouds of molecular gas. The investigators will map our galaxy to find clouds where stars are formed. They will also study the environment of our galaxy's spiral arms. The investigators have already mapped many of the positions of the clouds in our galaxy. Their new study will add a fourth dimension, the cloud speed. The speed is used to predict where clouds will collide to form spiral arms. These collisions can result in the birth of new stars. In partnership with expert 'information visualists', the investigator will bring their findings to the public through digital outreach and direct engagement at science and art festivals. These efforts will be attached to enhanced and interactive visualizations for astronomers. The processes by which gas flows together to form gaseous structures and stars is both a long and a difficult problem to solve in astronomy. Since the theory of gaseous spiral arms began, there have been arguments over whether spiral arms are long-lived, galaxy-scale density waves or short-lived myths of density confusions. In all of these theories, the spiral arms' gravitational potential brings large-scale combining gas flows. Theories differ on whether these flows are violent, causing shocks, or gentle, merely collecting gas without shocking it. It is not yet clear by what method of combining flows, whether driven by spiral arms or by other means, encourages the formation of giant molecular clouds (GMCs), or indeed whether combining flows are even necessary for GMC formation. The investigators hope to transform this field by developing and applying a new technique, Kinetic Tomography (KT). KT is a family of methods that transforms already existing astronomical measurements of the interstellar medium (ISM) into a direct measure of where gas is flowing together to form new structures or flowing apart in their destruction, as expressed in the distance-velocity diagram. The proposed work will test and expand the already-functional prototype KT method, which draws on cutting-edge applied math techniques such as compressed sensing. They will measure the rate and structure of convergence and divergence of the ISM, both on the large spiral arm scale and the smaller GMC scale. Furthermore, they will compare these measurements to existing data on molecular cloud structure and predictions from analytic theory and simulations.