摘要
A&A 708, A152 (2026) We investigate the properties of extreme emission line galaxies (EELGs) atz=4-9and their role in reionization. Compact, low-mass galaxies with intense optical emission lines are linked to elevated specific star formation rates (sSFRs) and recent bursts of star formation. Feedback in these systems may enable the leakage of ionizing radiation into the intergalactic medium. Using JWST/NIRSpec spectroscopy from the CAPERS, CEERS, and RUBIES surveys, we compile 160 NIRCam-selected EELGs in the EGS field. These galaxies show extreme rest-frame equivalent widths (EWs), with a median EW([O III]+H β )=1616Å and EW(H α )=763Å. They are low-mass (median log(M _(⋆) /M _(⊙) )=8.26) with high sSFRs (median 43 Gyr ⁻¹ ), above thez∼6main sequence. UV slopes are diverse, with a meanβ=-2.0 , and only 7% have extremely blue continua ( β<-2.6 ). Emission-line diagnostics suggest stellar populations as the primary ionizing source, although an AGN fraction of 14% is cannot be entirely ruled out. These galaxies are efficient ionizing photon producers, with mean log( ξ_(\rm ion)[Hz erg ⁻¹ ])=25.37, exceeding typical values at similar redshifts. Escape fractions, however, are heterogeneous: 16% of EELGs atz<7show escape fractions> 5% for both Ly αand LyC photons, while 82% lack detectable Ly αemission. The median inferred LyC escape fraction is modest (5%) but enhanced in compact super-Eddington systems with sSFR >25 Gyr ⁻¹ . These results indicate that EELGs contribute approximately 16-40% of the total ionizing emissivity required to sustain hydrogen reionization. EELGs are extremely compact, with a median effective radius of 0.49 kpc, and exhibit a recent star-formation burst. Our analysis indicates that sSFR and star-formation rate surface density are the primary drivers of their extreme emission line strengths.