Molecular outflows in local (U)LIRGs
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Date
2022
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Abstract
Luminous infrared galaxies (LIRGs) and ultra luminous infrared galaxies (ULIRGs), defined for having L_IR > 10^11 L_⊙ and L_IR > 10^12 L_⊙ respectively, were observed in large numbers in the 1980s by the Infrared Astronomical Satellite (IRAS). Most of them are believed to form after a major merger of two similarly massive spiral galaxies and represent a
key evolutionary stage, where events such as triggering of star formation and active galactic nucleus (AGN) occur, thereby deciding the fate of the galaxy. The study of (U)LIRGs and the processes taking place in them could lead to fundamental answers for understanding galaxy evolution.
This thesis studies the CO(2–1) emission from a subset of the Great Observatories All-Sky LIRG Survey (GOALS), conformed by 18 local (U)LIRGs (mean z = 0.026) observed with the Atacama Compact Array (ACA), at the Atacama Large Millimeter/submillimeter Array (ALMA). The main goal was to search for high-velocity components that could indicate the presence of molecular outflows and determine their incidence in the host galaxies. This was done by modeling the data as rotating disk galaxies to separate the emission into systemic and non-systemic components and estimate their dynamical parameters (for example, escape velocities and galactic masses).
Outflows with > 1% the total molecular mass were detected in 12 of the 18 sources at relatively low velocities, with only small fractions of the emission being able to escape the galactic potential. For the galaxies with stellar masses available in the literature, it was observed that they present higher star formation rates (SFRs) than those in the main sequence, although with lowering SFR for increasing M_star. Detailed analysis of mass outflow rates and AGN contributions to the bolometric luminosity support a scenario where feedback is produced mainly by stellar activity, as expected for starburst galaxies, finding that these outflows have little or no participation in the trend seen in the SFRs–M_star diagram.
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Tesis (Master in Astrophysics)--Pontificia Universidad Católica de Chile, 2022