The Geometry and Kinematics of Baryonic Feedback

Author: Prusinski, Nikolaus Zen

Year: 2026

Degree: Dissertation (Ph.D.)

Advisors: Steidel, Charles C.; Martin, D. Christopher

Committee Members: Hillenbrand, Lynne A.; Hopkins, Philip F.; Martin, D. Christopher; Mawet, Dimitri; Steidel, Charles C.

Option: Astrophysics

DOI: 10.7907/gnqa-tm83

Abstract

This thesis addresses the connection between the physics of galactic-scale baryonic feedback, the morphology and kinematics of gas in the multiphase circumgalactic medium (CGM), and host galaxy properties. Broadly speaking, each of the projects in this thesis attempts (through different datasets and techniques) to quantify how star formation is regulated in galaxies; the relevant observable being the gas and metal distributions in and around galaxies. The geometry and kinematics of interstellar, circumgalactic, and intergalactic gas provide insight into the efficacy and timescales over which galaxy-driven baryonic feedback processes operate.

Chapter 2 features the highest fidelity maps of the average z ~ 2 CGM to date using foreground/background galaxy pairs with angular separations < 30" in the Keck Baryonic Structure Survey (KBSS). The maps of covering fraction vs. transverse distance and line-of-sight velocity chart the changing gravitational influence the galaxy has over its CGM. Ly-alpha absorption shows a distinct transition near the virial radius of the average foreground galaxy and overall, dark matter halo mass appears to strongly modulate the kinematics, covering fraction, and spatial extent of CGM gas, a significant fraction of which may be unbound.

Chapter 3 presents new results on the spatial distribution and kinematics of nonresonant emission in and around z ~ 2 KBSS galaxies observed with the Keck Cosmic Web Imager (KCWI). Nonresonant Si II* emission lines have velocity spreads most consistent with a zero-velocity offset "ISM" component fit to their corresponding resonant Si II absorption lines. Extended Si II* halos are observed for the first time at z ~ 2 with a decreasing velocity spread with increasing transverse distance. At large radii, photon conservation appears to hold in that the flux "removed" by resonant absorption approximately equals the flux contributed by nonresonant emission.

Chapter 4 outlines the data reduction procedures needed to produce the integral field spectra used in this thesis. The KCWI data reduction pipeline stages I have improved or still need improvement are discussed. I introduce KCWIKit, a toolkit for mosaicking and correcting common systematics in integral field unit datacubes.

Finally, Chapter 5 introduces two ongoing projects considering how supermassive black holes couple to their host galaxies, their CGM, and intergalactic media (IGM) via Mpc-scale jets. Using KCWI, I am investigating the driving mechanisms behind Mpc-scale jets and searching for collisionally-excited emission from the giant jet bow shock. Such a detection would be the first detection of the warm-hot IGM (WHIM) in rest-frame UV emission and would open up a new means of mapping the distribution of metals in the IGM. The latter remains a critical frontier in accounting for the baryons in the universe and understanding the large-scale effects of galactic feedback.