J/ApJ/961/173 Extremely metal-poor galaxies at z<1 from DESI (Zou+, 2024)
A large sample of extremely metal-poor galaxies at z<1 identified from the DESI
Early Data.
Zou Hu, Sui J., Saintonge A., Scholte D., Moustakas J., Siudek M., Dey A.,
Juneau S., Guo W., Canning R., Aguilar J., Ahlen S., Brooks D.,
Claybaugh T., Dawson K., de la Macorra A., Doel P., Forero-Romero J.E.,
Gontcho Gontcho S. A, Honscheid K., Landriau M., Le Guillou L.,
Manera M., Meisner A., Miquel R., Nie J., Poppett C., Rezaie M., Rossi G.,
Sanchez E., Schubnell M., Seo H., Tarle G., Zhou Z., Zou S.
<Astrophys. J., 961, 173 (2024)>
=2024ApJ...961..173Z 2024ApJ...961..173Z
ADC_Keywords: Galaxies, dwarf; Spectra, optical; Abundances; Equivalent widths;
Redshifts; Surveys
Keywords: Metallicity ; Scaling relations ; Dwarf galaxies ; Redshift surveys
Abstract:
Extremely metal-poor galaxies (XMPGs) at relatively low redshift are
excellent laboratories for studying galaxy formation and evolution in
the early universe. Much effort has been spent on identifying them
from large-scale spectroscopic surveys or spectroscopic follow-up
observations. Previous work has identified a few hundred XMPGs. In
this work, we obtain a large sample of 223 XMPGs at z<1 from the early
data of the Dark Energy Spectroscopic Instrument (DESI). The oxygen
abundance is determined using the direct Te method based on the
detection of the [OIII]λ4363 line. The sample includes
95 confirmed XMPGs based on the oxygen abundance uncertainty; the
remaining 128 galaxies are regarded as XMPG candidates. These XMPGs
are only 0.01% of the total DESI observed galaxies. Their coordinates
and other properties are provided in the paper. The most XMPGs have an
oxygen abundance of ∼1/34 Z☉, a stellar mass of about
1.5x107M☉, and a star formation rate of 0.22M☉/yr. The
two most XMPGs present distinct morphologies suggesting different
formation mechanisms. The local environmental investigation shows that
XMPGs preferentially reside in relatively low-density regions. Many of
them fall below the stellar mass-metallicity relations (MZRs) of
normal star-forming galaxies. From a comparison of the MZR with
theoretical simulations, it appears that XMPGs are good analogs to
high-redshift star-forming galaxies. The nature of these XMPG
populations will be further investigated in detail with larger and
more complete samples from the ongoing DESI survey.
Description:
The Dark Energy Spectroscopic Instrument (DESI) is a multi-object
spectroscopic system installed at the prime focus of the Mayall 4m
telescope at Kitt Peak, in Arizona. It features a 3.2° field of
view and provide a continuous wavelength coverage of 3600-9800Å for
a R∼2000 in the blue end to 5000 in the red, which is high enough to
resolve the [OII] doublet.
The DESI spectroscopic targets include approximately 50 million
extragalactic and Galactic objects, mainly selected from the DESI
Legacy Imaging Surveys.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 154 95 Properties of our confirmed extremely metal-poor
galaxies (XMPGs)
table3.dat 154 128 Properties of our candidate XMPGs
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See also:
VI/141 : Nebular [OIII] collision strengths - SSB (Storey+, 2014)
VII/292 : DESI Legacy Imaging Surveys DR8 photometric redshifts (Duncan, 2022)
V/161 : DESI DR1 redshift catalog (DESI Col.+ 2025)
J/ApJS/132/37 : Spectroscopy of Southern warm IR galaxies (Kewley+, 2001)
J/ApJ/602/200 : HII regions abund. in blue compact galaxies (Izotov+, 2004)
J/ApJS/190/233 : Spectroscopy & abundances of SINGS galaxies (Moustakas+, 2010)
J/ApJS/188/32 : Breit-Pauli transition probabilities for SII (Tayal+, 2010)
J/ApJ/743/77 : Extremely metal-poor galaxies in SDSS (Morales-Luis+, 2011)
J/ApJ/765/140 : Stacked spectra of SDSS star forming galaxies (Andrews+, 2013)
J/A+A/568/L8 : VUDS emission line 0.2≲z≲0.9 galaxies (Amorin+, 2014)
J/ApJ/819/110 : EMP galaxies in SDSS. II. (Sanchez Almeida+ 2016)
J/other/RAA/17.41 : LAMOST metal-poor galaxies sample (Gao+, 2017)
J/ApJ/847/38 : Extreme emission line galaxies at z≲0.05 (Yang+, 2017)
J/ApJ/863/134 : SDSS low-metallicity blue compact dwarf galaxies (Hsyu+, 2018)
J/ApJ/896/77 : The PHLEK survey: oxygen & helium abundances (Hsyu+, 2020)
J/ApJS/258/11 : The COSMOS2020 catalog (Weaver+, 2022)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1/95] Sequential identifier
4- 7 A4 --- --- [DESI]
9- 27 A19 --- DESI Extremely metal-poor galaxy (XMPG)
name (JHHMMSS.ss+DDMMSSs)
29- 45 I17 --- TargetID [234520901058560/39633461119550747] DESI
target identifier
47- 55 F9.5 deg RAdeg [30.46/324.3] Right Ascension (J2000)
57- 65 F9.5 deg DEdeg [-27.3/66.7] Declination (J2000)
67- 72 F6.4 --- zspec [0.003/0.9] Spectroscopic redshift
74- 78 F5.2 mag rmag [17.2/25.4] DESI r-band magnitude
80- 83 F4.2 mag EBV [0/0.43] Reddening, E(B-V)
90- 93 F4.2 0.1nm EWOIII [1.6/3.24] Equivalent width of
[OIII]5007Å, in Angstroms
95- 100 F6.1 cm-3 Ne [100/1064] Electron volume density
102- 107 F6.1 cm-3 e_Ne [0/1156] Uncertainty in Ne
109- 115 F7.1 K Te [17632/23394] Electron temperature for
[OIII]
117- 122 F6.1 K e_Te [594/3542] Uncertainty in Te
124- 127 F4.2 [-] logOH [7.16/7.62] Oxygen abundance, 12+log(O/H)
129- 132 F4.2 [-] e_logOH [0.03/0.2] Uncertainty in logOH
134- 138 F5.2 [Msun] logMs [4.36/10.1] Log of stellar mass
140- 143 F4.2 [Msun] e_logMs [0.04/0.5] Uncertainty in logMs
145- 149 F5.2 [Msun/yr] logSFR [-3.8/1.6] Log of star formation rate
151- 154 F4.2 [Msun/yr] e_logSFR [0.1/0.14] Uncertainty in logSFR
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/128] Sequential identifier
5- 8 A4 --- --- [DESI]
10- 28 A19 --- DESI Extremely metal-poor galaxy (XMPG) name
(JHHMMSS.ss+DDMMSSs)
30- 46 I17 --- TargetID [234514848677892/39633478710462243] DESI
target identifier
48- 56 F9.5 deg RAdeg [3.98/339.6] Right Ascension (J2000)
58- 66 F9.5 deg DEdeg [-20.15/68.7] Declination (J2000)
68- 73 F6.4 --- zspec [0.002/0.96] Spectroscopic redshift
75- 79 F5.2 mag rmag [16.39/24.93] DESI r-band magnitude
81- 84 F4.2 mag EBV [0/0.35] Reddening, E(B-V)
91- 94 F4.2 0.1nm EWOIII [1.8/3.84]? Equivalent Width of
[OIII]5007Å, in Angstroms
96- 101 F6.1 cm-3 Ne [76/1648] Electron volume density
103- 108 F6.1 cm-3 e_Ne [0/1323] Uncertainty in Ne
110- 116 F7.1 K Te [16529/20709] Electron temperature for
[OIII]
118- 123 F6.1 K e_Te [480/3499] Uncertainty in Te
125- 128 F4.2 [-] logOH [7.5/7.7] Oxygen abundance, 12+log (O/H)
130- 133 F4.2 [-] e_logOH [0.03/0.3] Uncertainty in OH
135- 138 F4.2 [Msun] logMs [5.77/9.7] Log of stellar mass
140- 143 F4.2 [Msun] e_logMs [0.04/0.76] Uncertainty in logMs
145- 149 F5.2 [Msun/yr] logSFR [-2.4/1.6] Log of Star formation rate
151- 154 F4.2 [Msun/yr] e_logSFR [0.13/0.14] Uncertainty in logSFR
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 09-Apr-2026