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ABSTRACT We determine the O IIIλ5007 equivalent width (EW) distribution of 1. 700 z 2. 274 rest-frame ultraviolet (UV) -selected (MUV −19) star-forming galaxies in the GOODS North and South fields. We make use of deep HDUV broad-band photometry catalogues for selection and 3D-HST WFC3/IR grism spectra for measurement of line properties. The O IIIλ5007 EW distribution allows us to measure the abundance of extreme emission line galaxies (EELGs) within this population. We model a lognormal distribution to the O IIIλ5007 rest-frame EWs of galaxies in our sample, with location parameter μ = 4. 24 ± 0. 07 and variance parameter σ = 1. 33 ± 0. 06. This EW distribution has a mean O IIIλ5007 EW of 168 ± 1 Å. The fractions of z 2 rest-UV-selected galaxies with O IIIλ5007 EWs greater than 500, 750, and 1000 Å are measured to be 6. 8^+1. 0-₀. ₉{\ per\ cent}, 3. 6^+0. 7-₀. ₆{\ per\ cent}, and 2. 2^+0. 5-₀. ₄{\ per\ cent}, respectively. The EELG fractions do not vary strongly with UV luminosity in the range (−21. 6 MUV −19. 0) considered in this paper, consistent with findings at higher redshifts. We compare our results to z 5 and z 7 studies, where candidate EELGs have been discovered through Spitzer/IRAC colours, and we identify rapid evolution with redshift in the fraction of star-forming galaxies observed in an extreme emission line phase (a rise by a factor ∼10 between z 2 and z 7). This evolution is consistent with an increased incidence of strong bursts in the galaxy population of the reionization era. While this population makes a sub-dominant contribution of the ionizing emissivity at z 2, EELGs are likely to dominate the ionizing output in the reionization era.
Boyett et al. (Thu,) studied this question.