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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 (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/Myr-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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 212 48 The Sample of metal-poor galaxies in LAMOST survey
See also: V/146 : LAMOST DR1 catalogs (Luo+, 2015) V/149 : LAMOST DR2 catalogs (Luo+, 2016) : LAMOST DR4 Home Page Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
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
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
History: From electronic version of the journal
(End) Patricia Vannier [CDS] 07-Aug-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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