Spectroscopy of Extreme Emission Line Galaxies at z 2 and Implications for Galaxies in the Reionization Era
Abstract
Star forming galaxies have long been suggested as the primary ionizing agents responsible for reionization. There are two critical unknowns in the reionization calculation: 1) the ionizing photon production efficiency and 2) the ionizing photon escape fraction of z > 6 galaxies. Unfortunately, both the two quantities are difficult to measure directly at z > 6. Recent studies have demonstrated that galaxies in the reionization era have prominent [OIII]+H-beta emission, reflecting the rapidly rising star formation histories that dominate at early times. These motivate the need for a comprehensive interpretation of the spectral properties of extreme emission line galaxies (EELGs) at high redshift. In my thesis work, I have conducted a large spectroscopic survey with MMT, Keck, and Magellan to identify rest-frame UV and optical emission lines in over 200 EELGs at z ~ 2, where they can be studied in much greater detail. These systems show low stellar masses and large specific star formation rates that are similar to galaxies in the reionization era. I will present the results from this survey, discussing the stellar populations and nebular gas conditions of EELGs and constraining their ionizing photon production efficiencies and ionizing photon escape fractions. These galaxies are found to have large ionization parameters and low metallicities. Galaxies with larger rest-frame optical emission line equivalent widths are more efficient ionizing agents and have more extreme ionizing conditions of nebular gas which are conducive to the escape of ionizing photons. Using these results, I will summarize the nature of extreme emission line galaxies and constrain their contribution to the ionizing background. Finally, I will discuss the optimal strategy for spectroscopic investigation of galaxies at z > 6 with JWST/NIRSpec.
- Publication:
-
American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23540401T