Multiphase Galactic Outflows: Physical Properties and Feedback Effects
type: CreativeWork
description: Feedback mechanisms are invoked in theoretical models and cosmological simulations to regulate or even suppress star formation in galaxies. One feedback route is through galactic outflows, which eject large amounts of gas and thereby remove the fuel for future star formation. Such galactic outflows can be driven by active galactic nuclei (AGN) or processes associated with star formation such as supernovae or radiation pressure from young stellar populations. The goal of this thesis is to study outflows from an observational perspective in different phases to quantify their impact on their host galaxies comprehensively, primarily by using optical and millimetre band data from the Multi Unit Spectroscopic Explorer (MUSE) and the Atacama Large Millimeter/submillimeter Array (ALMA). In the first part of this thesis, I study the physical mechanisms driving outflows as well as whether outflows are capable of suppressing star formation using a study of molecular gas outflows with ALMA and archival data. In a sample of 50 local galaxies with outflow signatures in low-J carbon monoxide (CO) transitions, I find most outflows are consistent with the radiation pressure-driven or the energy-driven (but with a low coupling efficiency) models. Furthermore, most outflows are unable to escape the galaxy’s gravitational potential (with 5 % or less of outflowing gas exceeding the escape velocity), and the depletion time-scales of the galaxies’ total gas reservoirs are typically of the order of 10^8 years or more. Based on these findings, I conclude that outflows are unlikely to quench their entire host galaxy but might affect the central regions of the galaxy. Second, I investigate the physical conditions of the outflowing gas and the link between different gas phases in the galactic outflows. While there is observational evidence of outflows in many different phases, the connection between them and their relative importance is poorly understood. My results based on MUSE observations …
abstract: Feedback mechanisms are invoked in theoretical models and cosmological simulations to regulate or even suppress star formation in galaxies. One feedback route is through galactic outflows, which eject large amounts of gas and thereby remove the fuel for future star formation. Such galactic outflows can be driven by active galactic nuclei (AGN) or processes associated with star formation such as supernovae or radiation pressure from young stellar populations. The goal of this thesis is to study outflows from an observational perspective in different phases to quantify their impact on their host galaxies comprehensively, primarily by using optical and millimetre band data from the Multi Unit Spectroscopic Explorer (MUSE) and the Atacama Large Millimeter/submillimeter Array (ALMA). In the first part of this thesis, I study the physical mechanisms driving outflows as well as whether outflows are capable of suppressing star formation using a study of molecular gas outflows with ALMA and archival data. In a sample of 50 local galaxies with outflow signatures in low-J carbon monoxide (CO) transitions, I find most outflows are consistent with the radiation pressure-driven or the energy-driven (but with a low coupling efficiency) models. Furthermore, most outflows are unable to escape the galaxy’s gravitational potential (with 5 % or less of outflowing gas exceeding the escape velocity), and the depletion time-scales of the galaxies’ total gas reservoirs are typically of the order of 10^8 years or more. Based on these findings, I conclude that outflows are unlikely to quench their entire host galaxy but might affect the central regions of the galaxy. Second, I investigate the physical conditions of the outflowing gas and the link between different gas phases in the galactic outflows. While there is observational evidence of outflows in many different phases, the connection between them and their relative importance is poorly understood. My results based on MUSE observations …
author: Flütsch, Andrin
language: eng
keywords: Galaxy formation, AGN, Outflows, quasars, negative feedbacck, positive feedback
license: https://www.repository.cam.ac.uk/bitstreams/b0f4a1d9-414a-4cc1-bb8c-f8b414eb8e04/download
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2020-07-01
date modified: 2026-07-24T01:33:13Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.64236