Lyman Alpha Emission from Low-Redshift Star-Forming Galaxies as a Probe for Lyman Continuum Escape
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Date
2018-04-11
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Johns Hopkins University
Abstract
The goal of this thesis is to analyze far-ultraviolet spectra from nearby star-forming galaxies and investigate how the hydrogen Lyman alpha (Lyα) line at 1216 ̊A is re- lated to the host’s environmental parameters that determine Lyman continuum (LyC) escape. It has been suggested that Lyα can be used as a proxy for the escape of LyC radiation from UV-bright regions of nearby galaxies. LyC is of particular interest with respect to reionization of neutral atomic hydrogen in the universe over a redshift range from z ∼ 6 to z ∼ 12, which was highly dependent on the ux of ionizing LyC photons in the intergalactic medium. Expanding our understanding of the dynamics of the Lyα escape fraction (fLyα) from the local neutral hydrogen environment around star formation could be key to guiding searches for measurement of a total LyC escape fraction (fLyC) across all morphologies of galaxies. We will describe multiple Lyα projects to do this, including a Hubble Space Telescope (HST) observation program with the Cosmic Origins Spectrograph (COS) in Cycle 22 to complete a far-UV survey of nearby star-forming galaxies as an analog to early galaxies driving reionization, as well as a launch of an ultraviolet spectrograph built by the Johns Hopkins sounding
rocket group. This concludes with identification of galaxy candidates that indicate neutral hydrogen columns suggestive of high LyC escape fractions, as well as de ning methodology for future observations to identify LyC leak galaxies with inexpensive observation programs.
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Keywords
galaxy, instrumentation, physics, astrophysics, ultraviolet, spectroscopy, reionization