Molecular hydrogen and its ions in dark interstellar clouds and star forming regions

Persistent Link:
http://hdl.handle.net/10150/280192
Title:
Molecular hydrogen and its ions in dark interstellar clouds and star forming regions
Author:
Kulesa, Craig A.
Issue Date:
2002
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:
Fundamental observations of molecular hydrogen (H₂) in dark clouds, star forming regions, and radiation-dominated environments are presented, modeled, and interpreted. Through a weak infrared absorption line spectrum, the abundance of cold H₂ in dark molecular clouds and star forming regions is measured directly and compared with the abundance of its most commonly cited surrogate, CO. The derived abundance of CO is between 1.5 and 2.5 x 10⁻⁴ for the sample. The CO molecule thus represents about ⅓ of the total carbon budget in dense clouds. Also detected via infrared line absorption is the pivotal molecular ion H⁺₃ , yielding a direct measure of the cosmic ray ionization rate of H₂ in dark molecular clouds (between 1 and 5 x 10⁻¹⁷ s⁻¹), a process that instigates the complex ion-neutral chemical pathways that form many of the 120+ known molecular species deep inside interstellar clouds. These timely tests of theory are applied to the detailed submillimeter-wave study of the ρ Ophiuchi star forming cloud and photodissociation front, allowing partial disentanglement of the complicated physical and chemical structure of a star forming cloud. Yet H₂ and H⁺₃ continue to surprise and delight us with more mysteries. The formation, excitation and survival of molecules in unusual & hostile environments is highlighted by the discoveries of H⁺₃ in circumstellar disks of early-type stars, and of fluorescing H₂ in two harshly-irradiated filaments of the Crab Nebula. The role of H⁺₃ as a possible tracer of planet formation, and the evolution of H₂ in the interstellar medium is discussed. The study of H₂ in hostile environments is extended to the ensemble properties of extragalactic star forming regions, and applied to the Arp 299 merger system as a unique probe of the feedback of newly-formed hot stars, their fossil remains, and the molecular material which formed them.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Physics, Astronomy and Astrophysics.; Physics, Molecular.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Astronomy
Degree Grantor:
University of Arizona
Advisor:
Walker, Christopher K.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleMolecular hydrogen and its ions in dark interstellar clouds and star forming regionsen_US
dc.creatorKulesa, Craig A.en_US
dc.contributor.authorKulesa, Craig A.en_US
dc.date.issued2002en_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.abstractFundamental observations of molecular hydrogen (H₂) in dark clouds, star forming regions, and radiation-dominated environments are presented, modeled, and interpreted. Through a weak infrared absorption line spectrum, the abundance of cold H₂ in dark molecular clouds and star forming regions is measured directly and compared with the abundance of its most commonly cited surrogate, CO. The derived abundance of CO is between 1.5 and 2.5 x 10⁻⁴ for the sample. The CO molecule thus represents about ⅓ of the total carbon budget in dense clouds. Also detected via infrared line absorption is the pivotal molecular ion H⁺₃ , yielding a direct measure of the cosmic ray ionization rate of H₂ in dark molecular clouds (between 1 and 5 x 10⁻¹⁷ s⁻¹), a process that instigates the complex ion-neutral chemical pathways that form many of the 120+ known molecular species deep inside interstellar clouds. These timely tests of theory are applied to the detailed submillimeter-wave study of the ρ Ophiuchi star forming cloud and photodissociation front, allowing partial disentanglement of the complicated physical and chemical structure of a star forming cloud. Yet H₂ and H⁺₃ continue to surprise and delight us with more mysteries. The formation, excitation and survival of molecules in unusual & hostile environments is highlighted by the discoveries of H⁺₃ in circumstellar disks of early-type stars, and of fluorescing H₂ in two harshly-irradiated filaments of the Crab Nebula. The role of H⁺₃ as a possible tracer of planet formation, and the evolution of H₂ in the interstellar medium is discussed. The study of H₂ in hostile environments is extended to the ensemble properties of extragalactic star forming regions, and applied to the Arp 299 merger system as a unique probe of the feedback of newly-formed hot stars, their fossil remains, and the molecular material which formed them.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectPhysics, Astronomy and Astrophysics.en_US
dc.subjectPhysics, Molecular.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineAstronomyen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorWalker, Christopher K.en_US
dc.identifier.proquest3073241en_US
dc.identifier.bibrecord.b43472084en_US
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