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The Structure, Chemistry, and Evolution of Atomic and Molecular Gas in the Diffuse Interstellar Medium: An Observational Investigation- [electronic resource]
The Structure, Chemistry, and Evolution of Atomic and Molecular Gas in the Diffuse Interstellar Medium: An Observational Investigation- [electronic resource]
상세정보
- 자료유형
- 학위논문파일 국외
- 최종처리일시
- 20240214101259
- ISBN
- 9798379760915
- DDC
- 520
- 서명/저자
- The Structure, Chemistry, and Evolution of Atomic and Molecular Gas in the Diffuse Interstellar Medium: An Observational Investigation - [electronic resource]
- 발행사항
- [S.l.]: : The University of Wisconsin - Madison., 2023
- 발행사항
- Ann Arbor : : ProQuest Dissertations & Theses,, 2023
- 형태사항
- 1 online resource(225 p.)
- 주기사항
- Source: Dissertations Abstracts International, Volume: 85-01, Section: B.
- 주기사항
- Advisor: Stanimirovic, Snezana.
- 학위논문주기
- Thesis (Ph.D.)--The University of Wisconsin - Madison, 2023.
- 사용제한주기
- This item must not be sold to any third party vendors.
- 초록/해제
- 요약The interstellar medium (ISM) is organized in different phases with distinctive temperatures, densities, and ionization. The complex interplay between the different phases of the ISM governs the physical and chemical evolution of galaxies. In this thesis, I focus on characterizing the neutral phases of the ISM, particularly the atomic hydrogen (H I) and diffuse molecular gas, using observations at radio wavelengths. To interpret and contextualize our observations, I also compare observational results to chemical models and multiphase ISM simulations.I present a catalog of H I absorption comprising data from seven previous experiments, constituting the largest sample of sensitive (optical depth noise στ ≲ 10−2 ) H I absorption ever constructed. With this sample, I investigate correlations between the properties of the multi-phase atomic gas and other tracers of the interstellar environment from archival multi-wavelength datasets. I provide important constraints for the environments in which the cold H I (the cold neutral medium, "CNM") and molecular gas are likely to form from the diffuse atomic ISM. I also discuss observations of cold H I structures at physical scales ∼ 10 - 104 AU that appear to be overdense by at least an order of magnitude with respect to the mean density of the CNM. I argue that shocks are likely important in producing these structures and play an important role in shaping the CNM at small scales.To characterize the environments where H I is converted into diffuse molecular gas - a crucial early step in the process of molecular cloud formation - I use observations of H I at 21 cm wavelength and the molecular species HCO+, HCN, HNC, and C2H at 3 mm wavelength. I present the conditions necessary for H I to be converted into diffuse molecular gas and then compare these observational results to predictions from a photodissociation region (PDR) chemical model and multiphase ISM simulations. I show that the parameters derived from PDR models are implausible for the diffuse environments probed by these observations, arguing instead that HCO+ production through dynamical processes such as shocks or turbulent dissipation is likely in these directions.Finally, to directly test the claim that shocks are important drivers of diffuse interstellar chemistry, I present the largest observational survey to date of SiO - believed to be an unambiguous tracer of interstellar shocks - in absorption in the diffuse ISM. I detect SiO in 5/8 diffuse and translucent (non-star-forming) environments with abundances a few to a few hundred times greater than the typically assumed abundance in quiescent gas. I argue that the SiO in some of these directions is associated with de-accelerated shocks from stellar feedback events 0.2 - 2 Myr ago. I conclude by emphasizing the need for observational constraints on the distribution of Si in the gas phase and grain mantles, which are crucial for understanding the physics of grain processing and chemistry in the ISM.
- 일반주제명
- Astronomy.
- 일반주제명
- Astrophysics.
- 일반주제명
- Molecular chemistry.
- 키워드
- Atomic hydrogen
- 키워드
- Molecular gas
- 기타저자
- The University of Wisconsin - Madison Astronomy
- 기본자료저록
- Dissertations Abstracts International. 85-01B.
- 기본자료저록
- Dissertation Abstract International
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
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■00520240214101259
■006m o d
■007cr#unu||||||||
■020 ▼a9798379760915
■035 ▼a(MiAaPQ)AAI30530947
■040 ▼aMiAaPQ▼cMiAaPQ
■0820 ▼a520
■1001 ▼aRybarczyk, Daniel R.
■24510▼aThe Structure, Chemistry, and Evolution of Atomic and Molecular Gas in the Diffuse Interstellar Medium: An Observational Investigation▼h[electronic resource]
■260 ▼a[S.l.]:▼bThe University of Wisconsin - Madison. ▼c2023
■260 1▼aAnn Arbor :▼bProQuest Dissertations & Theses, ▼c2023
■300 ▼a1 online resource(225 p.)
■500 ▼aSource: Dissertations Abstracts International, Volume: 85-01, Section: B.
■500 ▼aAdvisor: Stanimirovic, Snezana.
■5021 ▼aThesis (Ph.D.)--The University of Wisconsin - Madison, 2023.
■506 ▼aThis item must not be sold to any third party vendors.
■520 ▼aThe interstellar medium (ISM) is organized in different phases with distinctive temperatures, densities, and ionization. The complex interplay between the different phases of the ISM governs the physical and chemical evolution of galaxies. In this thesis, I focus on characterizing the neutral phases of the ISM, particularly the atomic hydrogen (H I) and diffuse molecular gas, using observations at radio wavelengths. To interpret and contextualize our observations, I also compare observational results to chemical models and multiphase ISM simulations.I present a catalog of H I absorption comprising data from seven previous experiments, constituting the largest sample of sensitive (optical depth noise στ ≲ 10−2 ) H I absorption ever constructed. With this sample, I investigate correlations between the properties of the multi-phase atomic gas and other tracers of the interstellar environment from archival multi-wavelength datasets. I provide important constraints for the environments in which the cold H I (the cold neutral medium, "CNM") and molecular gas are likely to form from the diffuse atomic ISM. I also discuss observations of cold H I structures at physical scales ∼ 10 - 104 AU that appear to be overdense by at least an order of magnitude with respect to the mean density of the CNM. I argue that shocks are likely important in producing these structures and play an important role in shaping the CNM at small scales.To characterize the environments where H I is converted into diffuse molecular gas - a crucial early step in the process of molecular cloud formation - I use observations of H I at 21 cm wavelength and the molecular species HCO+, HCN, HNC, and C2H at 3 mm wavelength. I present the conditions necessary for H I to be converted into diffuse molecular gas and then compare these observational results to predictions from a photodissociation region (PDR) chemical model and multiphase ISM simulations. I show that the parameters derived from PDR models are implausible for the diffuse environments probed by these observations, arguing instead that HCO+ production through dynamical processes such as shocks or turbulent dissipation is likely in these directions.Finally, to directly test the claim that shocks are important drivers of diffuse interstellar chemistry, I present the largest observational survey to date of SiO - believed to be an unambiguous tracer of interstellar shocks - in absorption in the diffuse ISM. I detect SiO in 5/8 diffuse and translucent (non-star-forming) environments with abundances a few to a few hundred times greater than the typically assumed abundance in quiescent gas. I argue that the SiO in some of these directions is associated with de-accelerated shocks from stellar feedback events 0.2 - 2 Myr ago. I conclude by emphasizing the need for observational constraints on the distribution of Si in the gas phase and grain mantles, which are crucial for understanding the physics of grain processing and chemistry in the ISM.
■590 ▼aSchool code: 0262.
■650 4▼aAstronomy.
■650 4▼aAstrophysics.
■650 4▼aMolecular chemistry.
■653 ▼aAtomic hydrogen
■653 ▼aInterstellar medium
■653 ▼aPDR chemical model
■653 ▼aInterstellar chemistry
■653 ▼aMolecular gas
■690 ▼a0606
■690 ▼a0431
■690 ▼a0596
■71020▼aThe University of Wisconsin - Madison▼bAstronomy.
■7730 ▼tDissertations Abstracts International▼g85-01B.
■773 ▼tDissertation Abstract International
■790 ▼a0262
■791 ▼aPh.D.
■792 ▼a2023
■793 ▼aEnglish
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T16933538▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
■980 ▼a202402▼f2024
