J/A+A/691/A59 Extreme emission-line galaxies at z∼4-9 (Llerena+, 2024)
Physical properties of extreme emission-line galaxies at z∼4-9 from the
JWST CEERS survey.
Llerena M., Amorin R., Pentericci L., Arrabal Haro P., Backhaus B.E.,
Bagley M.B., Calabro A., Cleri N.J., Davis K., Dickinson M.,
Finkelstein S.L., Gawiser E., Grogin N.A., Hathi N.P., Hirschmann M.,
Kartaltepe J.S., Koekemoer A.M., McGrath E.J., Mobasher B., Napolitano L.,
Papovich C., Pirzkal N., Trump J.R., Wilkins S.M., Yung L.Y.A.
<Astron. Astrophys. 691, A59 (2024)>
=2024A&A...691A..59L 2024A&A...691A..59L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Redshifts ; Photometry, infrared ; Equivalent widths
Keywords: galaxies: evolution - galaxies: formation - galaxies: high-redshift -
galaxies: ISM - galaxies: starburst
Abstract:
Extreme emission line galaxies (EELGs) are typically characterized by
high equivalent widths (EWs) which are driven by elevated specific
star formation rates (sSFR) in low-mass galaxies with subsolar
metallicities and little dust. Such extreme systems are rare in the
local universe, but the number density of EELGs increases with
redshift. Such starburst galaxies are currently presumed to be the
main drivers of hydrogen reionization over 5.5<z<15, which serves to
motivate many of the searches for high-z EELGs.
We aim to characterize the physical properties of a sample of ∼730
EELGs at 4<z<9 photometrically selected from the CEERS survey using
JWST/NIRCam. We validate our method and demonstrate the main physical
properties of a subset of EELGs using NIRSpec spectra.
We create synthetic NIRCam observations of EELGs using empirical
templates based on ∼2000 local metal-poor starbursts to select EELGs
based on color-color criteria. We study their properties based on SED
fitting and flux excess from emission lines in the photometric
filters.
Our sample has a mean stellar mass of 107.84Msun with high sSFRs with
a mean value of 10-7.03yr-1. We consider a delayed-τ model for
the star formation history and find our sample of EELGs are young with
a mean value of the time after the onset of star formation of 45Myr.
We find that they have similar line ratios to local metal-poor
starbursts with high log([OIII]/Hβ)≳0.4-1 which indicates that
star formation may be the dominant source of ionization. Based on the
photometric fluxes, we find an increase of EW([OIII]+Hβ) with
sSFR and {SIGMA}SFR, and a decrease with age and stellar mass. The
sample of EELGs can reach {SIGMA}SFR>10M☉/yr/kpc2 which
indicate they are strong candidates of LyC leakers. Another indirect
indicator is the high values of O32>5 that can be reached for some
galaxies in the sample.
Description:
The complete CEERS program involves imaging with the NIRCam short and
long-wavelength channels in ten pointings, observed as coordinated
parallels to primary observations with the NIRSpec and the MidInfrared
Instrument (MIRI). In this paper, we used photometric data from NIRCam
and NIRSpec spectra. The CEERS observations were split into two
epochs. The first epoch was executed in June 2022, and the second in
December 2022. An additional third epoch of NIRSpec prism spectra
(pointings 11 and 12) was taken in February 2023, due to the MSA short
that affected prism 9 + 10 in December 2022. In total, 10 pointings
were taken with NIRCam imaging, including seven filters per pointing
(F115W, F150W, F200W, F277W, F356W, F410M, and F444W), reaching
5σ depths of ∼28.5-29.2(AB)mag for point sources for a total
area of ∼97arcmin2.
We used version v0.51.2 of the CEERS Photometric Catalogs (Finkelstein
et al. in prep.).
We estimate the fluxes of [OIII]+Hβ and Hα based on the
observed photometry. Based on the line fluxes, we estimate the
rest-frame EWs. We report our estimations in Table 2.
To obtain the physical properties of the sample of EELGs, we perform
SED fitting with only JWST photometry to have homogeneous data. We
consider the entire set of filters used in the CEERS surveys, which
are F115W, F150W, F200W, F277W, F356W, F410M, and F444W.
We report the obtained parameters in Table 3.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 109 736 Photometry information for the EELGs candidates
ordered by increasing CEERS ID number
table3.dat 90 736 SED parameters for the EELGs candidates ordered
by increasing CEERS ID number
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- ID CEERS ID
8- 17 F10.6 deg RAdeg Right ascension (J2000)
19- 27 F9.6 deg DEdeg Declination (J2000)
29- 46 F18.16 - zphot Photometric redshift
48 I1 --- Flag [0/1] Quality flag (1)
50- 53 I4 nJy F277W ?=- Flux in F277W filter
55- 56 I2 nJy e_F277W Flux in F277W filter uncertainty
58- 61 I4 nJy F356W Flux in F356W filter
63- 64 I2 nJy e_F356W Flux in F356W filter uncertainty
66- 69 I4 nJy F410M Flux in F410M filter
71- 72 I2 nJy e_F410M Flux in F410M filter uncertainty
74- 78 F5.1 10-21W/m2 FluxO3Hb Photometric flux of [OIII]+Hbeta
in 10-18ergs/cm2/s unit
80- 82 F3.1 10-21W/m2 e_FluxO3Hb Photometric flux uncertainty of [OIII]+Hbeta
in 10-18ergs/cm2/s unit
84- 87 F4.1 10-21W/m2 FluxHa ?=- Photometric flux of Halpha
in 10-18ergs/cm2/s unit
89- 91 F3.1 10-21W/m2 e_FluxHa ?=- Photometric flux uncertainty of Halpha
in 10-18ergs/cm2/s unit
93- 96 I4 0.1nm EWO3Hb Photometric rest-frame equivalent width of
[OIII]+Hbeta in Angstroem unit
98-100 I3 0.1nm e_EWO3Hb Photometric rest-frame equivalent width
uncertainty of [OIII]+Hbeta in
Angstroem unit
102-105 I4 0.1nm EWHa ?=- Photometric rest-frame equivalent width
of Halpha in Angstroem unit
107-109 I3 0.1nm e_EWHa ?=- Photometric rest-frame equivalent width
uncertainty of Halpha in Angstroem unit
--------------------------------------------------------------------------------
Note (1): Quality flag as follows:
0 = reliable photometry
1 = a source near a bright source, close to the edge of the detector,
or with low surface brightness
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- ID CEERS ID
8- 11 F4.2 [Msun] logM* Stellar mass
13- 16 F4.2 [Msun] e_logM* Stellar mass uncertainty
18- 22 F5.1 Msun/yr SFR Star formation rate
24- 28 F5.1 Msun/yr e_SFR Star formation rate uncertainty
30- 32 I3 Myr Age Age
34- 36 I3 Myr e_Age Age uncertainty
38- 41 F4.1 --- logU Ionization parameter
43- 45 F3.1 --- e_logU Ionization parameter uncertainty
47- 50 F4.2 --- Z* Stellar metallicity
52- 55 F4.2 --- e_Z* Stellar metallicity uncertainty
57- 60 F4.2 mag Av Absolute attenuation
62- 65 F4.2 mag e_Av Absolute attenuation uncertainty
67- 70 F4.2 kpc reff ?=- Physical size in F200W filter
72- 75 F4.2 kpc e_reff ?=- Physical size in F200W filter
uncertainty
77- 82 F6.2 Msun/yr/kpc2 SigmaSFR ?=- Star formation rate surface density
84- 90 F7.2 Msun/yr/kpc2 e_SigmaSFR ?=- Star formation rate surface density
uncertainty
--------------------------------------------------------------------------------
History:
From Mario Llerena, mario.llerenaona(at)inaf.it
Acknowledgements:
We thank the anonymous referee for the detailed review and useful
suggestions that helped to improve this paper. We wish to thank all
our colleagues in the CEERS collaboration for their hard work and
valuable contributions to this project. We wish to thank to Jorge
Sanchez-Almeida for providing us with the ASK templates used in this
paper. MLl acknowledges support from the PRIN 2022 MUR project
2022CB3PJ3 - First Light And Galaxy aSsembly (FLAGS) funded by the
European Union - Next Generation EU. RA acknowledges the support of
ANID FONDECYT Regular Grant 1202007. RA acknowledges financial support
from the Severo Ochoa grant CEX2021-001131-S funded by
MCIN/AEI/10.13039/501100011033.
(End) Patricia Vannier [CDS] 20-Aug-2024