Observational Tracers of Hot and Cold Gas in Isolated Galaxy Simulations

As part of the Maria Mitchell Observatory’s REU, I worked with Dr. Devin Silvia at MSU to compare simulations of isolated spiral galaxies with recent observations of the circumgalactic medium (CGM).

As the interface containing inflows and outflows between the interstellar and intergalactic media, the CGM plays an important role in the composition and evolution of galaxies. Using a set of isolated galaxy simulations over different initial conditions and star formation and feedback parameters, we investigated the evolution of CGM gas. Specifically, in light of recent observational studies, we computed the radial column density profiles and covering fractions of various observable ion species (H I, C IV, O VI, Mg II, Si III) for each simulated galaxy. Taking uniformly random sightlines through the CGM of each simulated galaxy, we found the abundance of gas absorbers and analyzed their contribution to the overall column density along each sightline. By identifying the prevalence of high column density absorbers, we sought to characterize the distribution and evolution of observable ion species in the CGM.

We also noticed that a subset of our isolated galaxy simulations produced and maintained a stable precipitating CGM that fuels high rates of sustained star formation. This disagrees with observed spiral galaxy at low redshift, which tend to have relatively subdued rates of star formation. Based on our starting simulation parameters, we conjectured that this resulted from an initial overdensity of gas in the CGM, making it unrealistic as a model for low redshift galaxies. However, they may still be decent proxies for galaxies at higher redshift, which tend to have more hot gas farther out in the CGM.

I presented this research at the 231st Meeting of the AAS in Washington, D.C. on January 9, 2018. You can download my poster here!