The History of Enrichment of the Intergalactic Medium Using Cosmological Simulations

Persistent Link:
http://hdl.handle.net/10150/194237
Title:
The History of Enrichment of the Intergalactic Medium Using Cosmological Simulations
Author:
Oppenheimer, Benjamin Darwin
Issue Date:
2008
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
I investigate the chemical evolution of the Universe in a series of cosmological hydrodynamic simulations with the purpose of finding a self-consistent evolutionary scenario of galaxy formation able to reproduce key observables focusing on the enrichment of the intergalactic medium (IGM). The most successful models I run and analyze use the scalings of momentum-driven feedback whereby UV photons generated during the Main Sequence stage accelerate dust-driven winds while providing a significantly larger energy budget than from supernovae alone. The success of this outflow model relies on its ability to drive highly mass-loaded winds from small galactic haloes. These feedback relations, supported by observations of local starburst, are inserted into simulations at all epochs, reproducing observables including the C IV column density and linewidth distributions at z=6->1.5 and the O VI forest at z=0-0.5. Outflows at z>=5 propagate early nucleosynthetic products traced by C IV and lower ionization species into an otherwise metal-free IGM. Continual outflows at the peak ages of star formation (z=5->1.5) produce a non-evolving cosmic mass density of C IV despite continual enrichment increasing IGM metallicity by a factor of ten. The z=0-0.5 O VI forest is composed of weaker absorbers tracing photo-ionized diffuse IGM metals, sometimes injected by primordial galaxies, and stronger absorbers tracing recently injected metals, often unable to escape their parent haloes and sometimes collisionally ionized. Tracking the individual histories of metals in outflows shows the average outflow travels ~100 physical kpc and returns to galaxies on an average timescale of 1-2 Gyr; this result implies metals in superwinds do not remain in the IGM for a Hubble time and are more likely to rejoin galaxies. Metal absorbers aligned with Lyman-alpha are examined in detail, finding that the two often trace different phases of gas with the former tracing an inhomogeneous distribution of metals exhibiting turbulence imparted during the outflow phase dissipating on a Hubble timescale. I find this is the first model to self-consistently reproduce the wide range of IGM observables spanning the history of heavy metal production while being consistent with key galaxy observables. The link between star formation and galactic superwinds requires that a successful model of galaxy formation reproduces both the evolution of galaxies and the IGM.
Type:
text; Electronic Dissertation
Keywords:
cosmological simulations; intergalactic medium; galaxy formation; chemical enrichment; quasar absorption lines
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Astronomy; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Dave, Romeel J

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleThe History of Enrichment of the Intergalactic Medium Using Cosmological Simulationsen_US
dc.creatorOppenheimer, Benjamin Darwinen_US
dc.contributor.authorOppenheimer, Benjamin Darwinen_US
dc.date.issued2008en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractI investigate the chemical evolution of the Universe in a series of cosmological hydrodynamic simulations with the purpose of finding a self-consistent evolutionary scenario of galaxy formation able to reproduce key observables focusing on the enrichment of the intergalactic medium (IGM). The most successful models I run and analyze use the scalings of momentum-driven feedback whereby UV photons generated during the Main Sequence stage accelerate dust-driven winds while providing a significantly larger energy budget than from supernovae alone. The success of this outflow model relies on its ability to drive highly mass-loaded winds from small galactic haloes. These feedback relations, supported by observations of local starburst, are inserted into simulations at all epochs, reproducing observables including the C IV column density and linewidth distributions at z=6->1.5 and the O VI forest at z=0-0.5. Outflows at z>=5 propagate early nucleosynthetic products traced by C IV and lower ionization species into an otherwise metal-free IGM. Continual outflows at the peak ages of star formation (z=5->1.5) produce a non-evolving cosmic mass density of C IV despite continual enrichment increasing IGM metallicity by a factor of ten. The z=0-0.5 O VI forest is composed of weaker absorbers tracing photo-ionized diffuse IGM metals, sometimes injected by primordial galaxies, and stronger absorbers tracing recently injected metals, often unable to escape their parent haloes and sometimes collisionally ionized. Tracking the individual histories of metals in outflows shows the average outflow travels ~100 physical kpc and returns to galaxies on an average timescale of 1-2 Gyr; this result implies metals in superwinds do not remain in the IGM for a Hubble time and are more likely to rejoin galaxies. Metal absorbers aligned with Lyman-alpha are examined in detail, finding that the two often trace different phases of gas with the former tracing an inhomogeneous distribution of metals exhibiting turbulence imparted during the outflow phase dissipating on a Hubble timescale. I find this is the first model to self-consistently reproduce the wide range of IGM observables spanning the history of heavy metal production while being consistent with key galaxy observables. The link between star formation and galactic superwinds requires that a successful model of galaxy formation reproduces both the evolution of galaxies and the IGM.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectcosmological simulationsen_US
dc.subjectintergalactic mediumen_US
dc.subjectgalaxy formationen_US
dc.subjectchemical enrichmenten_US
dc.subjectquasar absorption linesen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineAstronomyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorDave, Romeel Jen_US
dc.identifier.proquest2889en_US
dc.identifier.oclc659749937en_US
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