Investigating Star Formation Feedback Through Gas Kinematics in Nearby Galaxies

Abstract

Many stages of the stellar life cycle release energy and momentum into the surrounding interstellar medium within a galaxy. This feedback can have profound effects on the host galaxy. This thesis investigates the role of stellar feedback in star-forming galaxies in the local Universe through multiwavelength observations of gas kinematics.

First, I study extraplanar diffuse ionized gas (eDIG) which is thought to be produced by gas ejected from the midplane by repeated supernova explosions. By comparing molecular and ionized gas rotation curves derived from a sub-sample of intermediate inclination star-forming galaxies from the EDGE-CALIFA Survey, I find that ~75% of my sample galaxies have smaller ionized gas rotation velocities than the molecular gas. I suggest and show that the lower ionized gas rotation velocity can be attributed to a significant contribution from eDIG in a thick disk which rotates more slowly than gas in the midplane. As a direct follow up to this study, I use a sample of edge-on galaxies selected from the CALIFA survey to directly investigate the prevalence, properties, and kinematics of eDIG. I find that 60% of these galaxies show a decrease in the ionized gas rotation velocity as a function of height above the midplane. The ionization of the eDIG is dominated by star-forming complexes. These studies reveal the pervasiveness and importance of this phase in local star-forming galaxies.

Next, I study stellar feedback in the extreme environment of the nuclear starburst in the nearby galaxy NGC 253. Using ALMA observations with 0.5 pc resolution, I detect blueshifted absorption and redshifted emission (P-Cygni profiles) in multiple spectral lines towards three of the super star clusters (SSCs). This is direct evidence for outflows of dense molecular gas from these SSCs. Through a comparison of the outflow properties with predictions from simulations, I find that the outflows are most likely powered by dust-reprocessed radiation pressure or O-star stellar winds. The observed outflows will have very substantial effects on the clusters' evolution. Finally, I find that the arrangement of the SSCs may be morpho-kinematically consistent with a ring or crossing streams from the larger-scale gas flows which fuel the starburst.