J/A+A/706/A261 EELG phys. prop. and ion. efficiency (Gimenez-Alcazar+, 2026)
J-PAS: First identification, physical properties and ionization efficiency of
extreme emission line galaxies.
Gimenez-Alcazar A., Amorin R., Vilchez J.M., Hernan-Caballero A.,
Gonzalez-Otero M., Arroyo-Polonio A., Iglesias-Paramo J.,
Lumbreras-Calle A., Fernandez-Ontiveros J.A., Bonatto L.,
Gonzalez Delgado R.M., Kehrig C., Torralba A., Rahna P.T., Jimenez-Teja Y.,
Marquez I., Breda I., Alvarez-Candal A., Abramo R., Alcaniz J., Benitez N.,
Bonoli S., Carneiro S., Cenarro J., Cristobal-Hornillos D., Dupke R.,
Ederoclite A., Hernandez-Monteagudo C., Marin-Franch A.,
Mendes de Oliveira C., Moles M., Sodre L.Jr, Taylor K., Varela J.,
Vazquez Ramio.H.
<Astron. Astrophys. 706, A261 (2026)>
=2026A&A...706A.261G 2026A&A...706A.261G (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; Stars, emission ; Redshifts ;
Spectroscopy ; Equivalent widths ; Optical
Keywords: galaxies: evolution - galaxies: photometry - galaxies: star formation
Abstract:
Extreme emission line galaxies (EELGs) are expected to have an
important contribution to the star formation activity and
mass assembly in galaxies. Specifically. EELGs are also promising
candidates to have a leading role in the cosmic reionization as their
interstellar medium may allow a significant fraction of their ionizing
photons to escape (>5%). Finding low-redshift analogues of these
high-z galaxies is therefore essential to characterize the physical
conditions in the ISM of these galaxies and understand the processes
that reionized the Universe.
We aim to develop a robust and efficient method for the photometric
identification of EELGs using the J-PAS survey. J-PAS will cover
approximately 8500deg2 of the sky with 54 narrow-band filters in the
optical range plus i-SDSS, enabling detailed studies of the physical
properties of these galaxies. In this work, we focus on an initial
subset of the survey: a 30 square degree area with complete
observations in all bands.
We combine equivalent width (EW) measurements from J-PAS narrow-band
photometry with artificial intelligence tech- niques to identify
galaxies with emission lines exceeding 300Å in any emission line.
We validate our selection using spectroscopic data from DESI/DR1 and
characterize the selected sample through spectral energy distribution
(SED) fitting with CIGALE.
We identify 917 EELGs up to z=0.8 over 30deg2, achieving a purity of
95% and a completeness of 96% for i-SDSS<22.5mag. Importantly, AGN
contamination has been carefully considered and is estimated to be
around 5%. Furthermore, a cross-match with DESI yields 79
counterparts, whose redshifts are in excellent agreement with our
photometric estimates, thereby confirming the reliability of our
redshift determination. In addition, the derived emission line fluxes
are in good agreement with spectroscopic measurements, reinforcing the
robustness of our methodology. Moreover, the selected sample reveals
strong correlations between ionizing photon production efficiency
(ksiion) and EW(Hβ), which are consistent with previous
observational studies at low and high redshift and theoretical
expectations. Finally, most of the sources surpass the ionizing
efficiency threshold required for reionization, highlighting their
relevance as local analogues of early-universe galaxies.
Description:
Two tables with photometric, structural, and emission line properties
of selected Extreme Emission Line Galaxies (EELGs) from J-PAS.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 198 917 Derived SED Parameters
table2.dat 323 917 Emission line quantities
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- TileID J-PAS tile identifier
6- 10 I5 --- Number Source number within the tile
12- 29 F18.14 deg RAdeg Right Ascension (J2000)
31- 48 F18.15 deg DEdeg Declination (J2000)
50- 60 F11.9 --- z Spectroscopic or photometric redshift
62- 71 F10.8 arcsec Reff Effective radius enclosing specified
fraction of flux
74- 92 F19.16 [Msun] logMstar Stellar mass from SED fitting (1)
94-113 F20.18 [Msun] e_logMstar 1-sigma uncertainty from Bayesian
analysis on logMstar (1)
115-135 F21.18 [Msun/yr] logSFR10 Star formation rate averaged over
last 10Myr (1)
137-155 F19.17 [Msun/yr] e_logSFR10 1-sigma uncertainty from Bayesian
analysis on logSFR10 (1)
157-175 F19.17 mag E(B-V) Dust attenuation
177-198 E22.19 mag e_E(B-V) 1-sigma uncertainty from Bayesian
analysis on E(B-V)
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Note (1): Stellar mass and SFR are derived using CIGALE with parametric SFHs,
Charlot & Bruzal (2019, see 2003MNRAS.344.1000B 2003MNRAS.344.1000B) stellar populations,
Chabrier (2003PASP..115..763C 2003PASP..115..763C) IMF, and Dale et al. (2014ApJ...784...83D 2014ApJ...784...83D)
dust models.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- TileID J-PAS tile identifier
6- 10 I5 --- Number Source number within the tile
12- 22 F11.9 --- z Spectroscopic or photometric redshift
24- 41 F18.15 10+7Hz/J xiHalpha ? Ionizing photon production
efficiency from H-alpha (in Hz/erg
unit) (1)
43- 62 F20.18 10+7Hz/J e_xiHalpha ? 1-sigma uncertainty on xi_Halpha
64- 81 F18.15 10+7Hz/J xiHbeta ? Ionizing photon production
efficiency from H-beta (in Hz/erg
unit) (1)
83-102 F20.18 10+7Hz/J e_xiHbeta ? 1-sigma uncertainty on xi_Hbeta
104-124 F21.16 10-20W/m2/nm FHalpha ? H-alpha line flux
(in 10-19erg/s/cm^2/Å unit)
126-144 F19.16 10-20W/m2/nm e_FHalpha ? 1-sigma uncertainty on FHalpha
(in 10-19erg/s/cm^2/Å unit)
146-169 F24.18 10-20W/m2/nm FHbeta ? H-beta line flux
(in 10-19erg/s/cm^2/Å unit)
171-190 F20.16 10-20W/m2/nm e_FHbeta ? 1-sigma uncertainty on FHbetaa
(in 10-19erg/s/cm^2/Å unit)
192-212 F21.16 0.1nm EWHalpha ? H-alpha equivalent width
(in Å unit)
214-233 F20.16 0.1nm e_EWHalpha ? 1-sigma uncertainty on EWHalpha
(in Å unit)
235-257 F23.17 0.1nm EWHbeta ? H-beta equivalent width
(in Å unit)
259-279 F21.16 0.1nm e_EWHbeta ? 1-sigma uncertainty on EWHbeta
(in Å unit)
281-303 F23.16 0.1nm EWOIII5007 ? Line [O III] 5007 A equivalent width
(in Å unit)
305-323 F19.15 0.1nm e_EWOIII5007 ? 1-sigma uncertainty on EWOIII5007
(in Å unit)
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Note (1): xi values assume fesc = 0, i.e., all Lyman continuum photons are
reprocessed into Balmer lines.
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Acknowledgements:
Antonio Gimenez Alcazar, agimenez(at)iaa.es
(End) Patricia Vannier [CDS] 07-Jan-2026