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Unveiling the Structure of the Circumgalactic Medium of High-Redshift Galaxies via Emission and Absorption Lines


Li, Zhihui (2024) Unveiling the Structure of the Circumgalactic Medium of High-Redshift Galaxies via Emission and Absorption Lines. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/42cq-6x31.


The circumgalactic medium (CGM), namely the gaseous matter beyond the stars and interstellar medium of a galaxy and within the virial radius of its dark matter halo, plays a pivotal role in governing crucial aspects of galaxy evolution. This thesis focuses on investigating the multiphase, clumpy structure of the CGM through the application of state-of-the-art numerical simulations, the development of novel semi-analytic models, and comprehensive analyses involving comparison with high-resolution, spatially resolved observational data obtained from the world's largest ground-based telescopes.

In this thesis, Chapter 2 represents a theoretical investigation into the fate of cool clouds within a hot ambient medium, which offers new insights into predicting the destiny of cool clouds based on observed CGM properties. Chapters 3 and 4 detail endeavors to model spatially resolved Lyα emission spectra obtained from SSA22 Lyα Blob 1 and 2 to constrain the cool gas properties, employing a multiphase, clumpy radiative transfer (RT) model for the CGM. Chapter 5 offers a theoretical exploration on extracting and interpreting physical parameters of cool gas in the CGM from Lyα spectra using physically realistic RT models. Chapter 6 introduces a novel method to self-consistently reproduce the spatially extended Lyα emission from the CGM of twelve extreme emission line galaxies at z ~ 2, marking the first successful attempt to model spatially varying Lyα emission within a physically realistic CGM framework. Chapter 7 introduces ALPACA, a new semi-analytic model for simulating low-ionization state (LIS) metal absorption lines in the clumpy CGM. Applying ALPACA to model CIIλ1334 absorption line profiles in star-forming galaxies at 2 < z < 3, the study reveals the intricate physical and kinematic structure of the CGM, and it underscores the necessity of integrating emission and absorption line modeling to effectively break the intrinsic degeneracy of complex CGM models. Concluding the thesis, Chapter 8 offers a brief summary and outlines potential applications of the newly developed CGM models in the James Webb Space Telescope (JWST) era.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Galaxies; Interstellar Medium; Circumgalactic Medium; Radiative Transfer
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Astronomy
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Steidel, Charles C.
Group:Astronomy Department
Thesis Committee:
  • Hillenbrand, Lynne A. (chair)
  • Hopkins, Philip F.
  • Steidel, Charles C.
  • El-Badry, Kareem J.
Defense Date:21 May 2024
Funding AgencyGrant Number
Record Number:CaltechTHESIS:06042024-015417159
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for ch.2 adapted for ch.3 adapted for ch.4 adapted for ch.5 adapted for ch.6 adapted for ch.7
Li, Zhihui0000-0001-5113-7558
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16498
Deposited By: Zhihui Li
Deposited On:06 Jun 2024 23:29
Last Modified:14 Jun 2024 21:11

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