The Green Bank Ammonia Survey: Probing the evolution of star-forming regions from filaments to cores

Rachel Friesen
University of Toronto

Abstract

Stars form within molecular clouds. Recent surveys of dust continuum emission of Galactic star-forming regions have shown that these clouds are highly filamentary. Dense molecular cores, the individual birth sites of stars, are largely embedded within these filaments. The star formation efficiency is thus strongly dependent on how these structures form and evolve, but continuum surveys alone cannot provide the kinematic data needed to investigate gas flows and stability. Here, I will present results from the Green Bank Ammonia Survey (GAS), a large program using the 100 m Green Bank Telescope, which provides this critical kinematic counterpoint to continuum surveys of nearby star-forming regions. GAS has mapped the major star-forming molecular clouds within 500 pc of the Sun in emission from ammonia (NH3) and other chemical species that preferentially trace cold, dense gas. With GAS, we are
1) evaluating the scales on which dense gas structures appear gravitationally stable,
2) tracking the dissipation of turbulence and the evolution of angular momentum from filaments to cores, and
3) quantitatively testing predictions of models of core and filament formation via mass flows and accretion.