J/ApJ/959/48 Metallicities for emission line galaxies from HALO7D (Pharo+, 2023)
Dwarf galaxies show little ISM evolution from z∼1 to z∼0: a spectroscopic study
of metallicity, star formation, and electron density.
Pharo J., Guo Y., Calvo G.B., Teppala T., Bian F., Carleton T., Faber S.,
Guhathakurta P., Koo D.C.
<Astrophys. J., 959, 48 (2023)>
=2023ApJ...959...48P 2023ApJ...959...48P
ADC_Keywords: Galaxies, dwarf; Spectra, optical; Abundances; Redshifts
Keywords: Metallicity ; Dwarf galaxies ; Star formation ;
Emission line galaxies ; Galaxies
Abstract:
We present gas-phase metallicity measurements for 583 emission line
galaxies at 0.3<z<0.85, including 388 dwarf galaxies with
log(M*/M☉)<9.5, and explore the dependence of the metallicity
on the stellar mass and star formation (SF) properties of the
galaxies. Metallicities are determined through the measurement of
emission lines in very deep (∼7hr exposure) Keck/DEIMOS spectra taken
primarily from the HALO7D survey. We measure metallicity with three
strong-line calibrations (O3Hβ, R23, and O3O2) for the overall
sample, as well as with the faint [NeIII]λ3869 and
[OIII]λ4363 emission lines for 112 and 17 galaxies where robust
detections were possible. We construct mass-metallicity relations
(MZR) for each calibration method, finding MZRs consistent with other
strong-line results at comparable redshift, as well as with z∼0
galaxies. We quantify the intrinsic scatter in the MZR as a function
of mass, finding it increases with lower stellar mass. We also measure
a weak but significant correlation between increased MZR scatter and
higher specific star formation rate (SFR). We find a weak influence of
SFR in the fundamental metallicity relation as well, with an SFR
coefficient of α=0.21. Finally, we use the flux ratios of the
[OII]λλ3727,3729 doublet to calculate gas electron
density in ∼1000 galaxies with log(M*/M☉)<10.5 as a function
of redshift. We measure low electron densities (ne∼25cm-3) for z<1
galaxies, again consistent with z∼0 conditions, but measure higher
densities (ne∼100cm-3) at z>1. These results all suggest that
there is little evolution in star-forming interstellar medium
conditions from z∼1 to z=0, confirmed with a more complete sample of
low-mass galaxies than has previously been available in this redshift
range.
Description:
The data used in this paper are comprised of very deep optical spectra
of ∼2400 galaxies observed with Keck/DEIMOS, and are described in
full detail in the HALO7D catalog paper, where the published
redshifts, line fluxes, and other measurements may be found
(Pharo+ 2022, J/ApJS/261/12).
The spectra were primarily taken by the HALO7D program
(PI: Guhathakurta; Cunningham+ 2019ApJ...876..124C 2019ApJ...876..124C), a program
primarily designed to observe faint Milky Way halo stars in the
COSMOS, EGS, and GOODS-North CANDELS fields.
Additional programs expand the sample to include GOODS-South,
including DEEPwinds (PI: Faber), N168D (PI: Livermore) and
HALO7D-GOODSS (PI: Kirby). The total observations comprise a sample of
2444 target galaxies, including 1255 low-mass galaxies across four
CANDELS fields, as well as 1189 more massive galaxies.
All spectra used in this project were obtained by the DEep Imaging
Multi-Object Spectrograph (DEIMOS) instrument at the Keck Observatory.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 162 583 Metallicity catalog
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See also:
J/A+A/448/955 : Abundances of emission galaxies in SDSS-DR3 (Izotov+, 2006)
J/ApJ/706/599 : Hα and UV SFR in the local volume (Lee+, 2009)
J/ApJS/193/13 : Spitzer/IRAC sources in the EGS I. SEDs (Barro+, 2011)
J/ApJS/193/30 : UV-to-FIR analysis of sources in the EGS. II. (Barro+, 2011)
J/ApJ/744/44 : Hα and UV fluxes in nearby galaxies (Weisz+, 2012)
J/ApJS/203/24 : Structural param. of galaxies in CANDELS (van der Wel+, 2012)
J/ApJ/765/140 : Stacked spectra of SDSS star forming galaxies (Andrews+, 2013)
J/ApJS/206/8 : COSMOS/UltraVISTA Ks-selected catalogs v4.1 (Muzzin+, 2013)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)
J/ApJ/795/165 : Line ratios in z∼2-3 gal. from KBSS-MOSFIRE (Steidel+, 2014)
J/ApJ/801/97 : GOODS-S & UDS stellar mass cat. from CANDELS (Santini+, 2015)
J/ApJ/844/171 : Lyα profile in 43 Green Pea galaxies (Yang+, 2017)
J/ApJS/243/22 : CANDELS/SHARDS multiwavelength cat. in GOODS-N (Barro+, 2019)
J/ApJ/919/143 : HST-WFC3/IR grism sp. for CANDELS z∼1-2 galaxies (Henry+, 2021)
J/ApJS/256/44 : LEGA-C DR3: HR sp. of 0.6<z<1 gal. (van der Wel+, 2021)
J/ApJS/261/12 : Deep redshift survey with Keck/DEIMOS sp. (Pharo+, 2022)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- ID HALO7D identifier
18- 23 F6.4 --- zH7 [0/0.9] Redshift from HALO7D catalog
25- 35 F11.7 deg RAdeg [53/215.5] Right Ascension (J2000)
37- 47 F11.7 deg DEdeg [-28/62.4] Declination (J2000)
49- 54 F6.3 [Msun] logMs [7.7/11.5] Log, Galaxy stellar mass
56- 59 F4.2 [Sun] Z-O3Hb [7/9.3] Metallicity, O3Hb line ratio
61- 64 F4.2 [Sun] Z-R23 [7/9.4] Metallicity, R23 line ratio
66- 69 F4.2 [Sun] Z-O3O2 [7.3/9.1] Metallicity, O3O2 line ratio
71- 76 F6.2 [Sun] Z-Ne3O2 [7/8.7]?=-99 Metallicity, Ne3O2 line
ratio
78- 83 F6.2 [Sun] Z-Te [7.3/8.5]?=-99 Metallicity, from
Excitation Temperature
85- 89 F5.2 --- O3Hb [0.09/13.3] Emission line ratio,
[OIII]5007Å/Hβ
91- 94 F4.2 --- e_O3Hb [0.05/4.6] Uncertainty in O3Hb
96- 100 F5.2 --- R23 [0.14/10.1] Emission line ratio,
[OIII]4959,5007+[OII]3727,3729/Hβ
102- 105 F4.2 --- e_R23 [0.03/0.6] Uncertainty in R23
107- 111 F5.2 --- O3O2 [0.49/26] Emission line ratio,
[OIII]4959,5007Å/[OII]3727,3729Å
113- 116 F4.2 --- e_O3O2 [0.04/2.8] Uncertainty in O3O2
118- 123 F6.2 --- Ne3O2 [0.06/1.9]?=-99 Emission line ratio,
[NeIII]3869Å/[OII]3727,3729Å
125- 131 F7.3 --- e_Ne3O2 [0.003/0.2]?=-99 Uncertainty in Ne3O2
133- 139 F7.2 10-19mW/m2 FNeIII [10/6836]?=-99 Dust-corrected
[NeIII]3869Å flux
141- 146 F6.2 10-19mW/m2 e_FNeIII [0.8/59]?=-99 Uncertainty in FNeIII
148- 153 F6.2 10-19mW/m2 FOIII [27/253]?=-99 Dust-corrected
[OIII]4363Å flux
155- 160 F6.2 10-19mW/m2 e_FOIII [2.7/27]?=-99 Uncertainty in FOIII
162 I1 --- Ex [0/1]? Excitation diagnostic flags (1)
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Note (1): Excitation diagnostic flags as follows:
0 = galaxy with ratios below the curve, so a purely star-forming galaxy;
1 = galaxy with ratios above the diagnostic curve, so a galaxy
with potential AGN contribution on the MeX diagnostic.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 28-Jan-2026