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J/A+A/448/955    Abundances  of emission galaxies in SDSS-DR3    (Izotov+, 2006)

The chemical composition of metal-poor emission-line galaxies in the Data Release 3 of the Sloan Digital Sky Survey. Izotov Y.I., Stasinska G., Meynet G., Guseva N.G., Thuan T.X. <Astron. Astrophys. 448, 955 (2006)> =2006A&A...448..955I
ADC_Keywords: Galaxies, spectra ; H II regions ; Abundances Keywords: galaxies: ISM - galaxies: starburst - galaxies: abundances Abstract: We have re-evaluated empirical expressions for the abundance determination of N, O, Ne, S, Cl, Ar and Fe taking into account the latest atomic data and constructing an appropriate grid of photoionization models with state-of-the art model atmospheres. Using these expressions we have derived heavy element abundances in the ∼310 emission-line galaxies from the Data Release 3 of the Sloan Digital Sky Survey (SDSS, III/241) with an observed Hbeta flux F(Hbeta)>10-14erg/s/cm2 and for which the [O III] 4363 emission line was detected at least at a 2sigma level, allowing abundance determination by direct methods. The oxygen abundance 12+logO/H of the SDSS galaxies lies in the range from ∼7.1 (Z/30) to ∼8.5 (0.7Z). The SDSS sample is merged with a sample of 109 blue compact dwarf (BCD) galaxies with high quality spectra, which contains extremely low-metallicity objects. We use the merged sample to study the abundance patterns of low-metallicity emission-line galaxies. We find that extremely metal-poor galaxies (12+logO/H<7.6, i.e. Z<Z/12) are rare in the SDSS sample. The alpha element to oxygen abundance ratios do not show any significant trends with oxygen abundance, in agreement with previous studies, except for a slight increase of Ne/O with increasing metallicity, which we interpret as due to a moderate depletion of O onto grains in the most metal-rich galaxies. The Fe/O abundance ratio is smaller than the solar value, by up to 1 dex at the high metallicity end. We also find that Fe/O increases with decreasing Hbeta equivalent width EW(Hbeta). We interpret this as a sign of strong depletion onto dust grains, and gradual destruction of those grains on a time scale of a few Myr. All the galaxies are found to have logN/O>-1.6, implying that they have a different nature than the subsample of high-redshift damped Lyalpha systems with log N/O of ~-2.3 and that their ages are larger than 100-300Myr. We confirm the apparent increase in N/O with decreasing EW(Hbeta), already shown in previous studies, and explain it as the signature of gradual nitrogen ejection by massive stars from the most recent starburst. Description: Table 1 contains emission line fluxes, the equivalent width and the observed flux of the Hbeta emission line and the extinction coefficient obtained from the spectra of the SDSS galaxies. Table 2 contains the electron temperature Te(O III), the oxygen abundance 12+logO/H, and the logarithms of the N/O, Ne/O, S/O, Cl/O, Ar/O, Fe/O abundance ratios in the SDSS galaxies. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file sdss.dat 54 309 *SDSS-DR3 names and positions table1.dat 332 309 Extinction-corrected fluxes of the emission lines in the spectra of the SDSS galaxies table2.dat 104 309 Element abundances in the SDSS galaxies
Note on sdss.dat: table added at CDS
See also: II/259 : The SDSS Photometric Catalog, Release 3 (Abazajian+ 2005) III/241 : Spectroscopy of SDSS Data Release 3 (SDSS-DR3) (ARC, 2005) http://www.sdss.org/dr3/ : SDSS-R3 Home Page Byte-by-byte Description of file: sdss.dat
Bytes Format Units Label Explanations
1- 14 A14 --- Name The spectrum number in the SDSS database 16- 24 F9.5 deg RAdeg ? Right Ascension (J2000) from SDSS-DR3 (1) 26- 34 F9.5 deg DEdeg ? Declination (J2000) from SDSS-DR3 (1) 36- 54 A19 --- SDSS SDSS name from SDSS-DR3 (1)
Note (1): One spectrum number, 0412-51931-038, could not be located in any of the releases DR2, DR3 and DR4, and had therefore no position. The SDSS name, based on J2000 position, exists only for the objects existing in the SDSS-DR3 (Cat. II/259)
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 14 A14 --- Name The spectrum number in the SDSS database 16- 20 F5.3 --- F3727 Extinction-corrected flux of the [O II] 3727 line relative to Hbeta 22- 26 F5.3 --- e_F3727 rms uncertainty on [O II] 3727 flux 28- 32 F5.3 --- F3750 Extinction-corrected flux of the H12 3750 line relative to Hbeta 34- 38 F5.3 --- e_F3750 rms uncertainty on H12 3750 flux 40- 44 F5.3 --- F3771 Extinction-corrected flux of the H11 3771 line relative to Hbeta 46- 50 F5.3 --- e_F3771 rms uncertainty on H11 3771 flux 52- 56 F5.3 --- F3797 Extinction-corrected flux of the H10 3797 line relative to Hbeta 58- 62 F5.3 --- e_F3797 rms uncertainty on H10 3797 flux 64- 68 F5.3 --- F3835 Extinction-corrected flux of the H9 3835 line relative to H beta 70- 74 F5.3 --- e_F3835 rms uncertainty on H9 3835 flux 76- 80 F5.3 --- F3868 Extinction-corrected flux of the [Ne III] 3868 line relative to Hbeta 82- 86 F5.3 --- e_F3868 rms uncertainty on [Ne III] 3868 flux 88- 92 F5.3 --- F4101 Extinction-corrected flux of the Hdelta 4101 line relative to Hbeta 94- 98 F5.3 --- e_F4101 rms uncertainty on Hdelta 4101 flux 100-104 F5.3 --- F4340 Extinction-corrected flux of the Hgamma 4340 line relative to Hbeta 106-110 F5.3 --- e_F4340 rms uncertainty on Hgamma 4340 flux 112-116 F5.3 --- F4363 Extinction-corrected flux of the [O III] 4363 line relative to Hbeta 118-122 F5.3 --- e_F4363 rms uncertainty on [O III] 4363 flux 124-128 F5.3 --- F4658 Extinction-corrected flux of the [Fe III] 4658 line relative to Hbeta 130-134 F5.3 --- e_F4658 rms uncertainty on [Fe III] 4658 flux 136-140 F5.3 --- F4686 Extinction-corrected flux of the He II 4686 line relative to Hbeta 142-146 F5.3 --- e_F4686 rms uncertainty on He II 4686 flux 148-152 F5.3 --- F4740 Extinction-corrected flux of the [Ar IV] 4740 line relative to Hbeta 154-158 F5.3 --- e_F4740 rms uncertainty on [Ar IV] 4740 flux 160-164 F5.3 --- F4861 [1.0] Extinction-corrected flux of the Hbeta 4861 line relative to Hbeta 166-170 F5.3 --- e_F4861 rms uncertainty on Hbeta 4861 flux 172-176 F5.3 --- F4959 Extinction-corrected flux of the [O III] 4959 line relative to Hbeta 178-182 F5.3 --- e_F4959 rms uncertainty on [O III] 4959 flux 184-188 F5.3 --- F4988 Extinction-corrected flux of the [Fe III] 4988 line relative to Hbeta 190-194 F5.3 --- e_F4988 rms uncertainty on [Fe III] 4988 flux 196-200 F5.3 --- F5525 Extinction-corrected flux of the [Cl III] 5517+5538 lines relative to Hbeta 202-206 F5.3 --- e_F5525 rms uncertainty on [Cl III] 5517+5538 flux 208-212 F5.3 --- F5876 Extinction-corrected flux of the He I 5876 line relative to Hbeta 214-218 F5.3 --- e_F5876 rms uncertainty on He I 5876 flux 220-224 F5.3 --- F6300 Extinction-corrected flux of the [O I] 6300 line relative to Hbeta 226-230 F5.3 --- e_F6300 rms uncertainty on [O I] 6300 flux 232-236 F5.3 --- F6312 Extinction-corrected flux of the [S III] 6312 line relative to Hbeta 238-242 F5.3 --- e_F6312 rms uncertainty on [S III] 6312 flux 244-248 F5.3 --- F6563 Extinction-corrected flux of the Halpha 6563 line relative to Hbeta 250-254 F5.3 --- e_F6563 rms uncertainty on Halpha 6563 flux 256-260 F5.3 --- F6584 Extinction-corrected flux of the [N II] 6584 line relative to Hbeta 262-266 F5.3 --- e_F6584 rms uncertainty on [N II] 6584 flux 268-272 F5.3 --- F6725 Extinction-corrected flux of the [S II] 6717+6731 lines relative to Hbeta 274-278 F5.3 --- e_F6725 rms uncertainty on [S II] 6717+6731 flux 280-284 F5.3 --- F7136 Extinction-corrected flux of the [Ar III] 7136 line relative to Hbeta 286-290 F5.3 --- e_F7136 rms uncertainty on [Ar III] 7136 flux 292-296 F5.3 --- F7325 Extinction-corrected flux of the [O II] 7320+7331 lines relative to Hbeta 298-302 F5.3 --- e_F7325 rms uncertainty on [O II] 7320+7331 flux 304-308 F5.3 --- F9069 Extinction-corrected flux of the [S III] 9069 line relative to Hbeta 310-314 F5.3 --- e_F9069 rms uncertainty on [S III] 9069 flux 316-319 F4.0 0.1nm EWHb Equivalent width of the Hbeta emission line 321-325 F5.0 10-19W/s/m2 FHb Observed Hbeta flux 327-332 F6.3 --- cHb Extinction coefficient
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 14 A14 --- Name The spectrum number in the SDSS database 16- 21 F6.4 10-4K Te Electron temperature Te(O III) 23- 28 F6.4 10-4K e_Te rms uncertainty on Te(O III) 30- 33 F4.2 --- 12+logO/H Oxygen abundance 12+logO/H 35- 38 F4.2 --- e_12+logO/H rms uncertainty on oxygen abundance 12+logO/H 40- 44 F5.2 --- logN/O Logarithm of the nitrogen-to-oxygen abundance ratio logN/O 46- 49 F4.2 --- e_logN/O rms uncertainty on logN/O 51- 55 F5.2 --- logNe/O Logarithm of the neon-to-oxygen abundance ratio logNe/O 57- 60 F4.2 --- e_logNe/O rms uncertainty on logNe/O 62- 66 F5.2 --- logS/O Logarithm of the sulfur-to-oxygen abundance ratio logS/O 68- 71 F4.2 --- e_logS/O rms uncertainty on logS/O 73- 77 F5.2 --- logAr/O Logarithm of the argon-to-oxygen abundance ratio logAr/O 79- 82 F4.2 --- e_logAr/O rms uncertainty on logAr/O 84- 88 F5.2 --- logCl/O Logarithm of the chlorine-to-oxygen abundance ratio logCl/O 90- 93 F4.2 --- e_logCl/O rms uncertainty on logCl/O 95- 99 F5.2 --- logFe/O Logarithm of the iron-to-oxygen abundance ratio logFe/O 101-104 F4.2 --- e_logFe/O rms uncertainty on logFe/O
Acknowledgements: Yuri Izotov, izotov(at)astro.physik.uni-goettingen.de
(End) Yuri Izotov [MAO, Ukraine], Patricia Vannier [CDS] 22-Nov-2005
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