J/ApJ/916/11 HETDEX [OIII] emitters. I. Low-z galaxies (Indahl+, 2021)
HETDEX [OIII] emitters.
I. A spectroscopically selected low-redshift population of low-mass,
low-metallicity galaxies.
Indahl B., Zeimann G., Hill G.J., Bowman W.P., Ciardullo R., Drory N.,
Gawiser E., Hopp U., Janowiecki S., Boylan-Kolchin M., Mentuch Cooper E.,
Davis D., Farrow D., Finkelstein S., Gronwall C., Kelz A., McQuinn K.B.W.,
Schneider D., Tuttle S.E.
<Astrophys. J., 916, 11 (2021)>
=2021ApJ...916...11I 2021ApJ...916...11I
ADC_Keywords: Galaxies, spectra; Redshifts; Equivalent widths ;
Photometry, ultraviolet; Photometry, ugriz
Keywords: Emission line galaxies ; Galaxies ; Galaxy abundances ;
Galaxy properties ; Star formation ; Galaxy evolution ; Spectroscopy ;
Surveys ; Astronomical techniques ; Optical astronomy
Abstract:
We assemble a sample of 17 low-metallicity (7.45<log(O/H)+12<8.12)
galaxies with z≤0.1 found spectroscopically, without photometric
preselection, in early data from the Hobby-Eberly Telescope Dark
Energy Experiment. Star-forming galaxies that occupy the lowest-mass
and lowest-metallicity end of the mass-metallicity relation tend to be
undersampled in continuum-based surveys as their spectra are typically
dominated by emission from newly forming stars. We search for galaxies
with high [OIII]λ5007/[OII]λ3727, implying highly
ionized nebular emission often indicative of low-metallicity systems.
With the Second Generation Low Resolution Spectrograph on the
Hobby-Eberly Telescope we acquired follow-up spectra, with higher
resolution and broader wavelength coverage, of each low-metallicity
candidate in order to confirm the redshift, measure the Hα and
[NII] line strengths, and, in many cases, obtain deeper spectra of the
blue lines. We find our galaxies are consistent with the
mass-metallicity relation of typical low-mass galaxies. However,
galaxies in our sample tend to have similar specific star formation
rates as the incredibly rare "blueberry" galaxies found by
Yang+ (2017, J/ApJ/847/38). We illustrate the power of spectroscopic
surveys for finding low-mass and low-metallicity galaxies and reveal
that we find a sample of galaxies that are a hybrid between the
properties of typical dwarf galaxies and the more extreme blueberry
galaxies.
Description:
We constructed our sample of low-metallicity [OIII] emitters from an
early internal HETDEX DR (iHDR1) consisting of a catalog of every
emission-line detection in the 8.16deg2 of the survey completed
between 2017 January 3 and 2019 February 9. The HETDEX survey is
conducted with the Visible Integral Field Unit Spectrograph (VIRUS),
which covers 3500-5500Å at an R∼800 (2Å/pixel dispersion).
Each galaxy in our sample was followed up with the LRS2 Red unit, an
IFS on the Hobby-Eberly Telescope at McDonald Observatory between
2019-10-30 and 2020-05-29. See Section 2.2.
Photometric data were collected from several surveys to perform SED
fitting of our sample. These data are discussed in detail in
Section 2.4.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 187 18 *Basic properties of objects in the sample
table3.dat 178 18 *Photometry from all surveys
table5.dat 299 18 *LRS2 flux measurements for lines measured
in LRS2 spectra
table6.dat 150 18 *Properties of the [OIII] emitting galaxies
in the sample
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Note on table1.dat and table3.dat and table5.dat and table6.dat:
O3ELG4b is not included in our sample as it did not meet our selection
criteria but its properties are presented since it is a companion of
O3ELG4a.
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See also:
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
II/371 : The Dark Energy Survey (DES): Data Release 2 (Abbott+, 2021)
VII/292 : DESI Legacy Imaging Surveys DR8 (Duncan, 2022)
J/A+AS/120/323 : Long-slit spectroscopy of UCM galaxies (Gallego+ 1996)
J/A+AS/141/371 : Low-mass stars evolutionary tracks (Girardi+, 2000)
J/A+A/448/955 : Abundances of emission galaxies in SDSS-DR3 (Izotov+, 2006)
J/A+A/459/85 : O/H and gas densities in star-forming galaxies (Nagao+, 2006)
J/ApJ/668/853 : Sp. of UltraStrong Emission Line galaxies (Kakazu+, 2007)
J/ApJS/178/247 : Hα and [NII] survey in local 11 Mpc (Kennicutt+, 2008)
J/ApJ/703/517 : The Spitzer Local Volume Legacy: IR photometry (Dale+, 2009)
J/ApJ/703/1672 : Far-IR and Hα fluxes in galaxies (Kennicutt+, 2009)
J/ApJS/192/5 : Emission-line galaxies from HETDEX pilot survey (Adams+, 2011)
J/ApJ/765/140 : Stacked spectra of SDSS star forming galaxies (Andrews+, 2013)
J/ApJ/777/18 : Stellar mass functions of galaxies to z=4 (Muzzin+, 2013)
J/ApJ/817/10 : Star-forming galaxy metallicities (Grasshorn Gebhardt+, 2016)
J/ApJ/819/73 : Metallicity evolution of COSMOS BCD sample (Lian+, 2016)
J/A+A/599/A71 : SDSS star-forming galaxies aperture-free (Duarte+, 2017)
J/ApJ/847/38 : Extreme emission line galaxies at z≲0.05 (Yang+, 2017)
J/ApJ/865/L1 : LAEs discovered with ultra-deep MUSE in UDF (Maseda+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- ID Identifier
10- 17 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
19- 25 F7.4 deg DEdeg Declination in decimal degrees (J2000)
27- 31 F5.3 --- z [0.027/0.096] Spectroscopic redshift
33- 38 F6.2 10-17mW/m2 O2-3727 [2/708] The [O II] 3727 flux (1)
40- 44 F5.2 10-17mW/m2 e_O2-3727 [0.5/80] Uncertainty in O2-3727
46- 51 F6.2 10-17mW/m2 Ne3-3869 [0.4/457] The [Ne III] 3869 flux (1)
53- 57 F5.2 10-17mW/m2 e_Ne3-3869 [0.3/16] Uncertainty in Ne3-3869
59- 64 F6.2 10-17mW/m2 H8 [-3/253] The H8 flux (1)
66- 70 F5.2 10-17mW/m2 e_H8 [0.4/12] Uncertainty in H8
72- 77 F6.2 10-17mW/m2 Ne3-3968 [-0.95/287] The [Ne III]+H7 3968 flux (1)
79- 83 F5.2 10-17mW/m2 e_Ne3-3968 [0.6/63] Uncertainty in Ne3-3968
85- 90 F6.2 10-17mW/m2 Hd [-0.6/281] The Hδ flux (1)
92- 96 F5.2 10-17mW/m2 e_Hd [0.3/14] Uncertainty in Hd
98-103 F6.2 10-17mW/m2 Hg [1.8/527] The Hγ flux (1)
105-109 F5.2 10-17mW/m2 e_Hg [0.2/59] Uncertainty in Hg
111-116 F6.2 10-17mW/m2 O3-4363 [-0.93/135] The [O III] 4363 flux (1)
118-122 F5.2 10-17mW/m2 e_O3-4363 [0.14/14] Uncertainty in O3-4363
124-128 F5.2 10-17mW/m2 He1-4471 [-3.8/35.5] The He I 4471 flux (1)
130-133 F4.2 10-17mW/m2 e_He1-4471 [0.3/4] Uncertainty in He1-4471
135-139 F5.2 10-17mW/m2 He2-4686 [-3.2/23] The He II 4686 flux (1)
141-144 F4.2 10-17mW/m2 e_He2-4686 [0.19/6] Uncertainty in He2-4686
146-151 F6.2 10-17mW/m2 Hb [3.3/952] The Hβ flux (1)
153-157 F5.2 10-17mW/m2 e_Hb [0.4/74] Uncertainty in Hb
159-165 F7.2 10-17mW/m2 O3-4959 [2.9/1297] The [O III] 4959 flux (1)
167-172 F6.2 10-17mW/m2 e_O3-4959 [0.6/150] Uncertainty in O3-4959
174-180 F7.2 10-17mW/m2 O3-5007 [11/4403] The [O III] 5007 flux (1)
182-187 F6.2 10-17mW/m2 e_O3-5007 [0.8/195] Uncertainty in O3-5007
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Note (1): Flux units are 10-17 ergs s-1 cm-2.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- ID Identifier
10- 14 F5.2 mag gLSmag [17.47/21.9] Apparent DESI LS g band magnitude
16- 21 F6.2 uJy gLSFlux [1.7/102.5] LS g band flux density
23- 26 F4.2 uJy e_gLSFlux [0.08/0.4] Uncertainty in gLSFlux
28- 32 F5.2 uJy rLSFlux [1.7/74] LS r band flux density
34- 37 F4.2 uJy e_rLSFlux [0.09/0.5] Uncertainty in rLSFlux
39- 43 F5.2 uJy zLSFlux [0.9/54] LS z band flux density
45- 48 F4.2 uJy e_zLSFlux [0.2/0.9] Uncertainty in zLSFlux
50- 54 F5.2 uJy W1LSFlux [0.06/32]? LS WISE 3.4 um band flux density
56- 59 F4.2 uJy e_W1LSFlux [1.5/3]? Uncertainty in W1LSFlux
61- 65 F5.2 uJy W2LSFlux [3/41]? LS WISE 4.6 um band flux density
67- 70 F4.2 uJy e_W2LSFlux [3/6]? Uncertainty in W2LSFlux
72- 77 F6.2 uJy W3LSFlux [27/465]? LS WISE 12.1 um band flux density
79- 84 F6.2 uJy e_W3LSFlux [80/185]? Uncertainty in W3LSFlux
86- 93 F8.2 uJy W4LSFlux [333/14004]? LS WISE 22.2 um band flux density
95-101 F7.2 uJy e_W4LSFlux [797/1290]? Uncertainty in W4LSFlux
103-107 F5.2 uJy gDESFlux [1.9/23.5]? DES g band flux density
109-112 F4.2 uJy e_gDESFlux [0.14/0.3]? Uncertainty in gDESFlux
114-118 F5.2 uJy rDESFlux [1.5/31.4]? DES r band flux density
120-123 F4.2 uJy e_rDESFlux [0.2/0.6]? Uncertainty in rDESFlux
125-129 F5.2 uJy iDESFlux [1.6/39.1]? DES g band flux density
131-134 F4.2 uJy e_iDESFlux [0.3/0.7]? Uncertainty in iDESFlux
136-140 F5.2 uJy zDESFlux [0.2/39]? DES z band flux density
142-145 F4.2 uJy e_zDESFlux [0.6/1.2]? Uncertainty in zDESFlux
147-151 F5.2 uJy YDESFlux [0.8/45.6]? DES Y band flux density
153-156 F4.2 uJy e_YDESFlux [2.28/4]? Uncertainty in YDESFlux
158-162 F5.2 uJy FUVFlux [0.7/57]? GALEX FUV band flux density
164-167 F4.2 uJy e_FUVFlux [0.2/10]? Uncertainty in FUVFlux
169-173 F5.2 uJy NUVFlux [1.13/56]? GALEX NUV band flux density
175-178 F4.2 uJy e_NUVFlux [0.4/6]? Uncertainty in NUVFlux
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- ID Identifier
10- 15 F6.2 10-17mW/m2 O2-3727 [-2.8/370.4] The [O II] 3727 flux (1)
17- 21 F5.2 10-17mW/m2 e_O2-3727 [1.2/92]? Uncertainty in O2-3727
23- 28 F6.2 10-17mW/m2 Ne3-3869 [-13/290] The [Ne III] 3869 flux (1)
30- 34 F5.2 10-17mW/m2 e_Ne3-3869 [0.8/61]? Uncertainty in Ne3-3869
36- 41 F6.2 10-17mW/m2 H8 [-24/131] The H8 flux (1)
43- 47 F5.2 10-17mW/m2 e_H8 [0.5/30]? Uncertainty in H8
49- 54 F6.2 10-17mW/m2 Ne3-3968 [-11.5/135] The [Ne III]+H7 3968 flux (1)
56- 60 F5.2 10-17mW/m2 e_Ne3-3968 [0.5/59]? Uncertainty in Ne3-3968
62- 67 F6.2 10-17mW/m2 Hd [-11.5/216] The Hδ flux (1)
69- 73 F5.2 10-17mW/m2 e_Hd [1/41]? Uncertainty in Hd
75- 80 F6.2 10-17mW/m2 Hg [-9.2/462] The Hγ flux (1)
82- 87 F6.2 10-17mW/m2 e_Hg [1.8/177]? Uncertainty in Hg
89- 94 F6.2 10-17mW/m2 O3-4363 [-5.4/130.3] The [O III] 4363 flux (1)
96-100 F5.2 10-17mW/m2 e_O3-4363 [0.8/44]? Uncertainty in O3-4363
102-106 F5.2 10-17mW/m2 He1-4471 [-7.7/33.4] The He I 4471 flux (1)
108-112 F5.2 10-17mW/m2 e_He1-4471 [1/13.4]? Uncertainty in He1-4471
114-119 F6.2 10-17mW/m2 He2-4686 [-11.2/25] The He II 4686 flux (1)
121-124 F4.2 10-17mW/m2 e_He2-4686 [0.7/7]? Uncertainty in He2-4686
126-131 F6.2 10-17mW/m2 Hb [0/992] The Hβ flux (1)
133-138 F6.2 10-17mW/m2 e_Hb [0.6/237]? Uncertainty in Hb
140-146 F7.2 10-17mW/m2 O3-4959 [0/1576] The [O III] 4959 flux (1)
148-153 F6.2 10-17mW/m2 e_O3-4959 [0.5/373]? Uncertainty in O3-4959
155-161 F7.2 10-17mW/m2 O3-5007 [0/4781] The [O III] 5007 flux (1)
163-169 F7.2 10-17mW/m2 e_O3-5007 [1/1147]? Uncertainty in O3-5007
171-175 F5.2 10-17mW/m2 He1-5876 [-0.6/84.4] The He I 5876 flux (1)
177-181 F5.2 10-17mW/m2 e_He1-5876 [0.6/18.5]? Uncertainty in He1-5876
183-187 F5.2 10-17mW/m2 O1-6300 [-2.9/10.97] The [O I] 6300 flux (1)
189-192 F4.2 10-17mW/m2 e_O1-6300 [0.4/2.61]? Uncertainty in O1-6300
194-198 F5.2 10-17mW/m2 S3-6312 [-1.8/9.85] The [S III] 6312 flux (1)
200-203 F4.2 10-17mW/m2 e_S3-6312 [0.48/3.5]? Uncertainty in S3-6312
205-209 F5.2 10-17mW/m2 N2-6548 [-0.42/9.75] The [N II] 6548 flux (1)
211-214 F4.2 10-17mW/m2 e_N2-6548 [0.13/7.15]? Uncertainty in N2-6548
216-222 F7.2 10-17mW/m2 Ha [11.5/2955] The Hα flux (1)
224-229 F6.2 10-17mW/m2 e_Ha [1.9/638]? Uncertainty in Ha
231-235 F5.2 10-17mW/m2 N2-6583 [-0.3/16.52] The [N II] 6583 flux (1)
237-240 F4.2 10-17mW/m2 e_N2-6583 [0.3/4.7]? Uncertainty in N2-6583
242-246 F5.2 10-17mW/m2 He1-6678 [-3.5/26.81] The He I 6678 flux (1)
248-251 F4.2 10-17mW/m2 e_He1-6678 [0.39/9]? Uncertainty in He1-6678
253-257 F5.2 10-17mW/m2 S2-6717 [-0.52/47.52] The [S II] 6717 flux (1)
259-263 F5.2 10-17mW/m2 e_S2-6717 [0.2/12]? Uncertainty in S2-6717
265-269 F5.2 10-17mW/m2 S2-6731 [-4.13/29.47] The [S II] 6731 flux (1)
271-274 F4.2 10-17mW/m2 e_S2-6731 [0.5/10]? Uncertainty in S2-6731
276-280 F5.2 10-17mW/m2 Ar3-7136 [-2.07/32.36] The [Ar III] 7136 flux (1)
282-285 F4.2 10-17mW/m2 e_Ar3-7136 [0.1/7]? Uncertainty in Ar3-7136
287-292 F6.2 10-17mW/m2 S3-9069 [-25.54/322.86] The [S III] 9069 flux (1)
294-299 F6.2 10-17mW/m2 e_S3-9069 [0.4/255]? Uncertainty in S3-9069
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Note (1): Fluxes are calibrated to the VIRUS [O III] 5007 measurement except
for O3ELG8 since this object does not LRS2-B observation. These lines
are marked with an asterisk. For this reason this table does not show
a LRS2 [O III] 5007 flux as it is the same as the VIRUS measurement
in Table 1. Flux units are 10-17 ergs s-1 cm-2.
-------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- ID Identifier
10- 14 F5.2 --- O3/O2 [0.7/13.2] VIRUS [O III]/[O II] line ratio
16- 19 F4.2 --- e_O3/O2 [0.1/3.7] Uncertainty in O3/O2
21- 24 F4.2 [-] logO/H [7.5/8.5] Log(O/H)+12 abundance ratio; see
Section 4.1
26- 29 F4.2 [-] e_logO/H [0.14/0.3] Lower uncertainty in logO/H
31- 34 F4.2 [-] E_logO/H [0.14/0.4] Upper uncertainty in logO/H
36- 40 F5.3 [-] logO/H* [7.55/7.91]? log(O/H)+12 abundance ratio (1)
42- 46 F5.3 [-] e_logO/H* [0.05/0.3]? Lower uncertainty in logO/H*
48- 52 F5.3 [-] E_logO/H* [0.08/0.4]? Upper uncertainty in logO/H*
54- 57 F4.2 Msun/yr SFRHa [0/1.3] Star Formation Rate from Halpha (2)
59- 62 F4.2 Msun/yr e_SFRHa [0/0.3] Lower uncertainty in SFRHa
64- 67 F4.2 Msun/yr E_SFRHa [0/0.3] Upper uncertainty in SFRHa
69- 72 F4.2 Msun/yr SFR100 [0/0.7] Star Formation Rate (3)
74- 77 F4.2 Msun/yr e_SFR100 [0/0.4] Lower uncertainty in SFR100
79- 82 F4.2 Msun/yr E_SFR100 [0/0.5] Upper uncertainty in SFR100
84- 87 F4.2 [Msun] logM [6.3/8.8] Log mass (3)
89- 92 F4.2 [Msun] e_logM [0.1/0.3] Lower uncertainty in logM
94- 97 F4.2 [Msun] E_logM [0.2/0.4] Upper uncertainty in logM
99- 103 F5.2 yr-1 sSFR [-9.6/-7.4] Specific Star Formation Rate (4)
105- 108 F4.2 yr-1 e_sSFR [0.18/0.4] Lower uncertainty in sSFR
110- 113 F4.2 yr-1 E_sSFR [0.25/0.5] Upper uncertainty in sSFR
115- 119 F5.2 mag E(B-V) [-0.01/0.2] The (B-V) color excess
121- 124 F4.2 mag e_E(B-V) [0/0.07] Lower uncertainty in E (B-V)
126- 129 F4.2 mag E_E(B-V) [0.01/0.07] Upper uncertainty in E (B-V)
131- 137 F7.2 0.1nm EWO3 [35/1272] Equivalent width
of [OIII]5007Å (5)
139- 144 F6.2 0.1nm e_EWO3 [3/160] Uncertainty in EWO3
146- 150 A5 --- f_EWO3 Flag on EWO3 (6)
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Note (1): From the metallicity values inferred from the electron
temperature direct method.
Note (2): Derived using the Hα line flux as discussed in Section 4.4.
Note (3): From the SED fitting discussed in Section 4.2.
Note (4): Derived from the Hα SFR and the stellar mass derived from MCSED.
We lacked the high-quality photometry required to determine reliable
SED fits for O3ELG10 so SED derived properties are estimates.
Note (5): Measured from using the continuum in the VIRUS spectra.
Note (6): A boolean True/False flag on the [OIII] EW measurement. True
indicates the object's continuum was not significantly detected in
the VIRUS spectra and thus the continuum levels are estimated
from the MCSED fit.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Dec-2022