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The Intergalactic and Circumgalactic Medium Surrounding Star-Forming Galaxies at Redshifts 2<z<3


Rudie, Gwen Charlena (2013) The Intergalactic and Circumgalactic Medium Surrounding Star-Forming Galaxies at Redshifts 2<z<3. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9PZ56T6.


We present measurements of the spatial distribution, kinematics, and physical properties of gas in the circumgalactic medium (CGM) of 2.0<z<2.8 UV color-selected galaxies as well as within the 2<z<3 intergalactic medium (IGM). These measurements are derived from Voigt profile decomposition of the full Lyα and Lyβ forest in 15 high-resolution, high signal-to-noise ratio QSO spectra resulting in a catalog of ∼6000 HI absorbers.

Chapter 2 of this thesis focuses on HI surrounding high-z star-forming galaxies drawn from the Keck Baryonic Structure Survey (KBSS). The KBSS is a unique spectroscopic survey of the distant universe designed to explore the details of the connection between galaxies and intergalactic baryons within the same survey volumes. The KBSS combines high-quality background QSO spectroscopy with large densely-sampled galaxy redshift surveys to probe the CGM at scales of ∼50 kpc to a few Mpc. Based on these data, Chapter 2 presents the first quantitative measurements of the distribution, column density, kinematics, and absorber line widths of neutral hydrogen surrounding high-z star-forming galaxies.

Chapter 3 focuses on the thermal properties of the diffuse IGM. This analysis relies on measurements of the ∼6000 absorber line widths to constrain the thermal and turbulent velocities of absorbing "clouds." A positive correlation between the column density of HI and the minimum line width is recovered and implies a temperature-density relation within the low-density IGM for which higher-density regions are hotter, as is predicted by simple theoretical arguments.

Chapter 4 presents new measurements of the opacity of the IGM and CGM to hydrogen-ionizing photons. The chapter begins with a revised measurement of the HI column density distribution based on this new absorption line catalog that, due to the inclusion of high-order Lyman lines, provides the first statistically robust measurement of the frequency of absorbers with HI column densities 14 ≲ log(NHI/cm-2) ≲ 17.2. Also presented are the first measurements of the column density distribution of HI within the CGM (50 <d < 300 pkpc) of high-z galaxies. These distributions are used to calculate the total opacity of the IGM and IGM+CGM and to revise previous measurements of the mean free path of hydrogen-ionizing photons within the IGM. This chapter also considers the effect of the surrounding CGM on the transmission of ionizing photons out of the sites of active star-formation and into the IGM.

This thesis concludes with a brief discussion of work in progress focused on understanding the distribution of metals within the CGM of KBSS galaxies. Appendix B discusses my contributions to the MOSFIRE instrumentation project.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:galaxies: evolution ; galaxies: formation ; galaxies: high-redshift ; instrumentation: spectrographs ; Intergalactic Medium ; quasars: absorption lines
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Astrophysics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Steidel, Charles C.
Group:Astronomy Department
Thesis Committee:
  • Hirata, Christopher M. (chair)
  • Steidel, Charles C.
  • Hillenbrand, Lynne A.
  • Martin, D. Christopher
  • Kollmeier, Juna A.
Defense Date:17 May 2013
Record Number:CaltechTHESIS:05202013-155707736
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7728
Deposited By: Gwen Rudie
Deposited On:28 May 2013 20:48
Last Modified:26 Oct 2021 17:36

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