J/A+A/708/A152 Extreme emission-line galaxies at z∼4-9 (Llerena+, 2026)
Extreme equivalent width-selected low-mass starbursts at z = 4-9:
insights into their role in cosmic reionization.
Llerena M., Pentericci L., Amorin R., Ferrara A., Dickinson M.,
Arevalo-Gonzalez F., Calabro A., Napolitano L., Mascia S., Arrabal Haro P.,
Begley R., Cleri N.J., Davis K., Hu W., Kartaltepe J.S., Koekemoer A.M.,
Lucas R.A., McGrath E., McLeod D.J., Papovich C., Stanton T.M., Taylor A.J.,
Tripodi R., Wang X., Yung L.Y.A.
<Astron. Astrophys. 708, A152 (2026)>
=2026A&A...708A.152L 2026A&A...708A.152L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Redshifts ; Photometry, infrared ; Equivalent widths
Keywords: galaxies: evolution - galaxies: formation - galaxies: high-redshift -
galaxies: ISM - galaxies: starburst
Abstract:
We investigate the properties of extreme emission line galaxies
(EELGs) at z=4-9 and 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([OIII/Hbeta])=1616Å and EW(Halpha)=763Å. They are low-mass
(median log(M*/M☉)=8.26) with high sSFRs (median 43Gyr-1),
above the z∼6 main sequence. UV slopes are diverse, with a
median value of beta=-2.0, and only 7% have extremely blue continua
(beta←2.6). Emission-line diagnostics suggest stellar populations as
the primary ionizing source, although an AGN fraction of 14% {cannot
be entirely ruled out. These galaxies are efficient ionizing photon
producers, with median log(xiion[Hz/erg])={25.37}, exceeding typical
values at similar redshifts. Escape fractions, however, are
heterogeneous: 16% of EELGs at z<7 show escape fractions >5% for
both Lyalpha and LyC photons, while 82% lack detectable Lya emission.
The median inferred LyC escape fraction is modest (5%) but enhanced in
compact super-Eddington systems with sSFR>25Gyr-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 0.49kpc, 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.
Description:
In this Table, we provide information about the galaxies in the
sample. We report their identification ID from the CEERS photometric
catalog and their spectroscopic ID (Spec ID) in each survey. We report
their coordinates, the corresponding spectroscopic survey and
disperser, spectroscopic redshifts, rest-frame EWs of bright emission
lines (Hbeta, [OIII], and Halpha), E(B-V) from SED modeling, sSFRs,
beta slopes, MUV, rest-frame optical effective radius, and
the inferred FLyC from the Cox models. The NLAGN candidates based
on the OHNO diagram are flagged with an N. The EELGs in the sample
classified as BLAGN are flagged with a B, while the ones with evidence
of a broad [OIII] component are flagged with an O.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 134 208 Informations about the galaxies in the sample
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See also:
J/A+A/691/A59 : Extreme emission-line galaxies at z∼4-9 (Llerena+, 2024)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- ID ID from CEERS photometric catalog
8- 10 A3 --- Flag Classification flag (1)
12- 17 I6 --- SpecID Spectroscopic ID
19- 27 F9.5 deg RAdeg Right ascension (J2000)
29- 36 F8.5 deg DEdeg Declination (J2000)
38- 41 A4 --- Survey Survey and disperser abbreviations (2)
43- 47 F5.3 --- zspec Spectroscopic redshift
49 A1 --- l_EWHb Limit flag on EWHb
50- 54 I5 0.1nm EWHb ?=- Hbeta equivalent width
56- 58 I3 0.1nm e_EWHb ?=- Hbeta equivalent width error
60- 63 I4 0.1nm EW[OIII] ?=- [OIII]5007 equivalent width
65- 68 I4 0.1nm e_EW[OIII] ?=- [OIII]5007 equivalent width error
70- 74 I5 0.1nm EWHa ?=- Halpha equivalent width
76- 79 I4 0.1nm e_EWHa ?=- Halpha equivalent width
81- 84 F4.2 mag E(B-V) E(B-V) from SED fitting
86 A1 --- l_logsSFR Limit flag on logsSFR
87- 90 F4.2 [Gyr-1] logsSFR log Specific star-formation rate
92- 95 F4.2 [Gyr-1] e_logsSFR ?=- log Specific star-formation rate
97-101 F5.2 --- betaUV ?=- UV beta slope
103-106 F4.2 --- E_betaUV ?=- UV beta slope error (upper value)
108-111 F4.2 --- e_betaUV ?=- UV beta slope error (lower value)
113-118 F6.2 mag UVMAG ?=- UV absolute magnitude
120-123 F4.2 kpc roptkpc ?=- Rest-frame optical effective radius
125-128 F4.2 kpc e_roptkpc ?=- Rest-frame optical effective radius
error
130-134 F5.2 --- logfescLyC ?=- Infered LyC escape fraction
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Note (1): Classification flag as follows:
B = Classified as BLAGN
N = Possible AGN (OHNO diagram)
O = Broad [OIII]
Note (2): Survey and disperser abbreviations:
CA-P = CAPERS-PRISM
C-P = CEERS-PRISM
R-P = RUBIES-PRISM
C-M = CEERS-MR
R-M = RUBIES-MR
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Acknowledgements:
Mario Llerenaona, mario.llerenaona(at)inaf.it
(End) Patricia Vannier [CDS] 05-Mar-2026