1. The mean ultraviolet spectrum of a representative sample of faint <italic>z</italic> ∼ 3 Lyman alpha emitters.
- Author
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Nakajima, Kimihiko, Ellis, Richard S, Fletcher, Thomas, Robertson, Brant E, and Iwata, Ikuru
- Subjects
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LYMAN line , *ULTRAVIOLET astronomy , *STELLAR evolution , *BALMER line , *STELLAR luminosity function , *GALACTIC redshift - Abstract
We discuss the rest-frame ultraviolet (UV) emission line spectra of a large (∼100) sample of low luminosity redshift
z ∼ 3.1 Lyman alpha emitters (LAEs) drawn from a Subaru imaging survey in the SSA22 survey field. Our earlier work based on smaller samples indicated that such sources have high [O iii]/[O ii] line ratios possibly arising from a hard ionizing spectrum that may be typical of similar sources in the reionization era. With optical spectra secured from VLT/VIMOS, we re-examine the nature of the ionizing radiation in a larger sample using the strength of the high ionization diagnostic emission lines of Ciii]λ1909, Civλ1549, Heiiλ1640, and O iii]λλ1661, 1666 Å in various stacked subsets. Our analysis confirms earlier suggestions of a correlation between the strength of Ly α and Ciii] emission and we find similar trends with broad-band UV luminosity and rest-frame UV colour. Using various diagnostic line ratios and our stellar photoionization models, we determine both the gas phase metallicity and hardness of the ionization spectrum characterized by ξion – the number of Lyman continuum photons per UV luminosity. We confirm our earlier suggestion that ξion is significantly larger for LAEs than for continuum-selected Lyman break galaxies, particularly for those LAEs with the faintest UV luminosities. We briefly discuss the implications for cosmic reionization if the metal-poor intensely star-forming systems studied here are representative examples of those at much higher redshift. [ABSTRACT FROM AUTHOR]- Published
- 2018
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