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Leveraging the Rest-Ultraviolet and Rest-Optical Spectra of Galaxies at 2 < z < 3


Theios, Rachel Lauren (2020) Leveraging the Rest-Ultraviolet and Rest-Optical Spectra of Galaxies at 2 < z < 3. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/kj2p-j718.


Galaxies at the peak of cosmic star formation (2 < z < 3) are fundamentally different from local galaxies, in terms of the properties of their massive stellar populations and physical conditions in the interstellar medium (ISM). This thesis presents a detailed analysis of the stellar and nebular properties of high-redshift galaxies, using the rest-frame UV and rest-frame optical spectra of galaxies from the Keck Baryonic Structure Survey (KBSS), a large, targeted spectroscopic survey of galaxies at 2 < z < 3.

Chapter 2 compares inferences of dust attenuation, star formation, and metallicity from strong nebular emission lines, the far-UV continuum, and spectral energy distribution (SED) fits. These results indicate that the majority of high-redshift galaxies display different dust properties than those at low redshift, and that the assumption of a dust attenuation curve can dramatically change inferred properties such as star formation rates (SFRs). I find that SFRs estimated using different methods only agree under specific combinations of assumptions, and caution that SFR calibrations established in the local Universe do not apply at higher redshifts.

Chapter 3 utilizes rest-UV absorption lines to study the outflow kinematics of high-redshift galaxies. I compare several velocity metrics used in the literature, and search for correlations between outflow velocity and galaxy properties. These results are consistent with the picture of winds driven by momentum injected into the ISM by stellar feedback. I confirm that large-scale outflows are ubiquitous at high redshift due to these galaxies' high SFRs and compact sizes.

Finally, Chapter 4 analyzes the systematic uncertainties involved in fitting stellar population synthesis (SPS) models to rest-UV spectra as well as the full SEDs of galaxies. I quantify differences in galaxy parameters estimated using different combinations of models and assumptions, and explore the dependence of the rest-UV portion of model spectra on stellar metallicity and population age.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Galaxies: evolution; galaxies: high-redshift; galaxies: interstellar medium
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.
Thesis Committee:
  • Hillenbrand, Lynne A. (chair)
  • Hopkins, Philip F.
  • Kirby, Evan N.
  • Martin, D. Christopher
  • Steidel, Charles C.
Defense Date:1 June 2020
Record Number:CaltechTHESIS:06052020-225431864
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Ch. 2.
Theios, Rachel Lauren0000-0002-4236-1037
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13783
Deposited By: Rachel Theios
Deposited On:15 Jun 2020 16:34
Last Modified:30 May 2023 22:19

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