Carnegie Mellon University

Astro Seminar

The origin and evolution of multiphase galaxy outflows

Star-forming galaxies are often observed to host galactic winds - gas that is flowing out of the galaxy in phases ranging from cold molecular clouds to hot X-ray emitting plasma. Although these outflows are routinely observed and play an important role in galaxy evolution, theoretically constraining their origin and properties has proven difficult. Explaining the prevalence and velocities of the cool ionized gas phase poses a particular challenge. In this talk, I will discuss a theoretical framework that explains these outflows, including a potential origin for the cool gas. Through a series of extremely high-resolution simulations run with the GPU-based Cholla code, I will demonstrate that in rapidly star-forming systems, dense disk gas can be pushed out by the collective effect of clustered supernovae, explaining the low-velocity material. Simultaneously, shredding and mixing of these clouds increases the density of the hot phase of the wind, leading to large-scale radiative losses that produce high velocity cool gas. In addition to explaining the nature of outflows themselves, these multiphase winds could potentially be a source of the cool photo-ionized gas that is found in abundance in galaxy halos.