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arXiv · 2512.08484

J-PAS: First Identification, Physical Properties and Ionization Efficiency of Extreme Emission Line Galaxies

A. Giménez-Alcázar·R. Amorín·J. M. Vílchez·A. Hernán-Caballero·M. González-Otero·A. Arroyo-Polonio·J. Iglesias-Páramo·A. Lumbreras-Calle·J. A. Fernández-Ontiveros·L. Bonatto·R. M. González Delgado·C. Kehrig·A. Torralba·P. T. Rahna·Y. Jiménez-Teja·I. Márquez·I. Breda·A. Álvarez-Candal·R. Abramo·J. Alcaniz·N. Benitez·S. Bonoli·S. Carneiro·J. Cenarro·D. Cristóbal-Hornillos·R. Dupke·A. Ederoclite·C. Hernández-Monteagudo·A. Marín-Franch·C. Mendes de Oliveira·M. Moles·L. Sodré Jr.·K. Taylor·J. Varela·H. Vázquez Ramió
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Abstract

Extreme emission line galaxies (EELGs) are key tracers of intense star formation and potential analogues of the sources that reionized the early Universe. Their low-redshift counterparts offer a unique opportunity to study the physical conditions that enable high ionizing-photon escape fractions. We present a robust method to photometrically identify EELGs in the J-PAS survey, which provides 56 optical bands over 8500 deg^2. Using data from a fully observed 30 deg^2 region, we combine narrow-band equivalent widths with machine-learning techniques to select galaxies with emission lines above 300 Å. The method achieves 95% purity and 96% completeness for $i_\mathrm{SDSS}<22.5$ mag. We identify 917 EELGs up to $z=0.8$; spectroscopic cross-matching with DESI/DR1 confirms the reliability of our redshifts and emission-line measurements. The selected galaxies show strong correlations between $ξ_\mathrm{ion}$ and EW([OIII]), consistent with previous low- and high-z studies. Most sources exceed the ionizing efficiency threshold required for reionization, reinforcing their role as local analogues of early-Universe galaxies.

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A. Giménez-Alcázar, R. Amorín, J. M. Vílchez, A. Hernán-Caballero, M. González-Otero, A. Arroyo-Polonio, J. Iglesias-Páramo, A. Lumbreras-Calle, J. A. Fernández-Ontiveros, L. Bonatto, R. M. González Delgado, C. Kehrig, A. Torralba, P. T. Rahna, Y. Jiménez-Teja, I. Márquez, I. Breda, A. Álvarez-Candal, R. Abramo, J. Alcaniz, N. Benitez, S. Bonoli, S. Carneiro, J. Cenarro, D. Cristóbal-Hornillos, R. Dupke, A. Ederoclite, C. Hernández-Monteagudo, A. Marín-Franch, C. Mendes de Oliveira, M. Moles, L. Sodré Jr., K. Taylor, J. Varela, H. Vázquez Ramió. 2025-12-09. J-PAS: First Identification, Physical Properties and Ionization Efficiency of Extreme Emission Line Galaxies. https://doi.org/10.1051/0004-6361%2F202557358

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