J/other/RAA/17.41 LAMOST metal-poor galaxies sample (Gao+, 2017)
A sample of metal-poor galaxies identified from the LAMOST spectral survey.
Gao Y.-L., Lian J.-H., Kong X., Lin Z.-S., Hu N., Liu H.-Y., Wang E.-C.,
Cao Z.-H., Hou Y.-H., Wang Y.-F., Zhang Y.
<Res. Astron. Astrophys. 17, 41 (2017)>
=2017RAA....17...41G 2017RAA....17...41G (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Redshifts ; Abundances ; Spectroscopy
Keywords: galaxies: abundances - galaxies: evolution - galaxies: starburst -
star formation
Abstract:
We present a sample of 48 metal-poor galaxies at z<0.14 selected from
92 510 galaxies in the LAMOST survey. These galaxies are identified by
their detection of the auroral emission line [OIII]λ4363 above
the 3σ level, which allows a direct measurement of electron
temperature and oxygen abundance. The emission line fluxes are
corrected for internal dust extinction using the Balmer decrement
method. With electron temperature derived from
[OIII]λλ4959,5007/[OIII]λ4363 and electron
density from [SII]λ6731/[SII]λ6717, we obtain the oxygen
abundances in our sample which range from
12+log(O/H)=7.63(0.09Z☉) to 8.46 (0.6Z☉). We find an
extremely metal-poor galaxy with 12+log(O/H)=7.63±0.01. With
multiband photometric data from FUV to NIR and Hα measurements,
we also determine the stellar masses and star formation rates, based
on the spectral energy distribution fitting and Hα luminosity,
respectively. We find that our galaxies have low and intermediate
stellar masses with 6.39≤log(M/M☉)≤9.27, and high star
formation rates (SFRs) with -2.18≤log(SFR/M☉yr-1)≤1.95. We
also find that the metallicities of our galaxies are consistent with
the local Te-based mass-metallicity relation, while the scatter is
about 0.28dex. Additionally, assuming the coefficient of α=0.66,
we find most of our galaxies follow the local mass-metallicity-SFR
relation, but a scatter of about 0.24dex exists, suggesting the
mass-metallicity relation is weakly dependent on SFR for those
metal-poor galaxies.
Description:
Among all galaxies from the LAMOST ExtraGAlactic Surveys (LEGAS), we
first select a subsample of metal-poor galaxies with emission line
flux ratios [NII]λ6583/Hα≤0.1, which yields 665
galaxies. Among them, we identify 237 objects with [OIII]λ4363
detection at ≥3σ. We inspect these 237 objects visually, and
find 73 of them are false detections. We also exclude 115 objects that
are HI regions in nearby large galaxies using optical images with SDSS
SkyServer. Finally, we check the right ascension and declination of
the remaining sources, and note that one object was observed twice by
LAMOST. We keep the observation that has better spectral quality.
As a consequence, our final sample consists of 48 galaxies, making up
only 0.05% of all the LAMOST galaxies until DR4 Q2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 212 48 The Sample of metal-poor galaxies in LAMOST survey
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See also:
V/146 : LAMOST DR1 catalogs (Luo+, 2015)
V/149 : LAMOST DR2 catalogs (Luo+, 2016)
http://dr4.lamost.org : LAMOST DR4 Home Page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- ID Sequential number (1)
4- 12 F9.5 deg RAdeg Right ascension (J2000) (2)
14- 22 F9.5 deg DEdeg Declinaiton (J2000) (2)
24- 28 F5.3 --- z Redshift (2)
30- 34 F5.3 --- I([OII]) Intensity of [OII]λ3727 line
relative to I(Hβ) (3)
36- 40 F5.3 --- I([OIII]a) Intensity of [OIII]λ4363 line
relative to I(Hβ) (3)
42- 46 F5.3 --- I([OIII]b) Intensity of [OIII]λ4953 line
relative to I(Hβ) (3)
48- 52 F5.3 --- I([OIII]c) Intensity of [OIII]λ5007 line
relative to I(Hβ) (3)
54- 58 F5.3 --- I(Ha) Intensity of Hα line
relative to I(Hβ) (3)
60- 64 F5.3 --- I([SII]a) Intensity of [SII]λ6717 line
relative to I(Hβ) (3)
66- 70 F5.3 --- I([SII]b) Intensity of [SII]λ6731 line
relative to I(Hβ) (3)
72- 79 F8.2 10-20W/m2 I(Hb) Intensity of Hβ line (4)
81- 86 F6.2 0.1nm EW(Hb) Hβ equivalent width (5)
88- 91 F4.2 mag E(B-V) Nebular color excess (6)
93- 96 F4.2 10+4K Te Electron temperature for [OIII]
line (7)
98-103 F6.2 cm-3 ne Electron density (8)
105-108 F4.2 --- 12+log(O/H)Te Oxygen abundance, 12+log(O/H)Te
110-114 F5.3 [Msun] logM Mass
116-121 F6.3 [Msun/yr] logSFR Star formation rate
123 I1 --- SDSS [0/1] Detected by SDSS ? (9)
125-130 F6.3 --- e_I([OII]) rms uncertainty on I([OII])
132-136 F5.3 --- e_I([OIII]a) rms uncertainty on I([OIII]a)
138-142 F5.3 --- e_I([OIII]b) rms uncertainty on I([OIII]b)
144-148 F5.3 --- e_I([OIII]c) rms uncertainty on I([OIII]c)
150-154 F5.3 --- e_I(Ha) rms uncertainty on I(Ha)
156-160 F5.3 --- e_I([SII]a) rms uncertainty on I([SII]a)
162-166 F5.3 --- e_I([SII]b) rms uncertainty on I([SII]b)
168-173 F6.2 10-20W/m2 e_I(Hb) rms uncertainty on I(Hb)
175-178 F4.2 0.1nm e_EW(Hb) rms uncertainty on EW(Hb)
180-183 F4.2 mag e_E(B-V) rms uncertainty on E(B-V)
185-188 F4.2 10+4K e_Te rms uncertainty on Te
190-195 F6.2 cm-3 e_ne rms uncertainty on ne
197-200 F4.2 --- e_12+log(O/H)Te rms uncertainty on 12+log(O/H)Te
202-206 F5.3 [Msun] e_logM Mass rms uncertainty on logM
208-212 F5.3 [Msun/yr] e_logSFR rms uncertainty on logSFR
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Note (1): ID is the serial number for every object and it will be referred to
throughout this paper.
Note (2): The position and redshift are obtained from the header of the
spectral FITS files.
Note (3): Reddening corrected emission line fluxes for our sample galaxies
measured from the LAMOST spectra are relative to Hβ.
Note (4): The Hβ fluxes are reported in units of 10-17 erg/s/cm2.
Note (5): The Hβ equivalent widths are given in units of Å, assuming
the mean values of observed flux intensities within 50Å wide component
around the Hβ as the continuum spectral flux intensities.
Note (6): The nebular color excesses are derived from the observed flux ratios
Hα/Hβ, and are assumed to be zero when the observed flux ratios
Hα/Hβ are less than 2.86.
Note (7): Electron temperatures are computed from the oxygen emission line
ratios [OIII]λλ4959,5007/[OIII]λ4363.
Note (8): Electron densities are calculated from an iterative process with
[OIII]λλ4959,5007/[OIII]λ4363 and
[SII]λ6717/[SII]λ6731 ratios.
Note (9): The flag numbers indicate the spectral detected states for our
objects with SDSS as follows:
1 = this object has been spectroscopically detected by SDSS
0 = this object has not been spectroscopically detected by SDSS
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 07-Aug-2017