The Interstellar Medium in Gravitationally Lensed Dusty Star-Forming Galaxies

Abstract

In this dissertation, I characterize the interstellar medium (ISM) in two gravitationally lensed dusty star-forming galaxies (DSFGs) from the South Pole Telescope (SPT) survey using observations from the Atacama Large Millimeter/submillimeter Array (ALMA), the most intensely star-forming galaxy and the most distant galaxy from this sample.In Chapter 1, I provide context and background about galaxies, gravitational lensing, and the ISM. In Chapter 2, I use high-resolution observations of [CII]158 and continuum dust emission to study SPT0346-52, a gravitationally lensed system at z=5.7.I use a pixelated, interferometric lens modeling code to ``de-lens'' the emission from SPT0346-52 and reconstruct its source-plane structure. With these reconstructions, I study the ``[CII]-deficit'', an observed phenomenon where the [CII]58/L_FIR ratio falls as Sigma_FIR increases. I then explore the kinematics of \cii 158 in SPT0346-52 in detail using position-velocity diagrams and the Toomre Q stability parameter. This work was published in Litke, et al. (2019). In Chapter 3, I follow up on SPT0346-52 with ALMA observations of [NII]205, [CII]158, [OI]146, [NII]122, [OI]63, and dust continuum in order to study the multi-phase ISM in this system.As in Chapter 2, I reconstruct the source-plane emission. I use the photoionization code Cloudy to model the conditions of the ISM. I explore deficits in all of the lines observed. I study the neutral phase of the ISM, the electron density in the diffuse ionized phase, and I discuss the implications of the non-detection of [OI]63. This work was published in Litke, et al. (2022). In Chapter 4, I discuss on-going work using ALMA observations of [CII]158, [OI]146, [NII]122, [OIII]88, and dust continuum to study the multi-phase ISM in the z=6.9 interacting galaxies of SPT0311-58.I use different line and continuum ratios to determine the ionization parameter and metallicity, and constrain the density of the neutral gas phase. In Chapter 5, I summarize the results of my work and the properties of these two systems, and discuss follow-up observations.