Carnegie Mellon University

Astro Lunch

The origin of multiphase galaxy outflows

Star-forming galaxies are often observed to have galactic winds - gas that is being ejected from the galaxy in phases ranging from cold molecular clouds to hot X-ray emitting plasma. While these multiphase outflows are routinely observed, theoretically constraining their origin has proven difficult. Explaining the prevalence and velocities of the cool ionized phase (T~10^4 K) in particular poses a challenge. In this talk, I will discuss a potential dual origin for this cool gas. Through a series of extremely high-resolution simulations run with the GPU-based Cholla code, I will show that in high star formation surface density systems, dense disk gas can be pushed out by the collective effect of clustered supernovae, explaining the low-velocity material. Simultaneously, shredding of these clouds increases the density of the hot phase of the outflow, 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 galaxy halos.