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J/ApJ/834/186  Metallicity of MPA-JHU SDSS-DR7 dwarf galaxies  (Douglass+, 2017)

Determining the large-scale environmental dependence of gas-phase metallicity in dwarf galaxies. Douglass K.A., Vogeley M.S. <Astrophys. J., 834, 186-186 (2017)> =2017ApJ...834..186D (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Abundances ; Redshifts Keywords: galaxies: abundances; galaxies: dwarf; galaxies: evolution Abstract: We study how the cosmic environment affects galaxy evolution in the universe by comparing the metallicities of dwarf galaxies in voids with dwarf galaxies in more dense regions. Ratios of the fluxes of emission lines, particularly those of the forbidden [OIII] and [SII] transitions, provide estimates of a region's electron temperature and number density. From these two quantities and the emission line fluxes [OII]λ3727, [OIII]λ4363, and [OIII]λλ4959,5007, we estimate the abundance of oxygen with the direct Te method. We estimate the metallicity of 42 blue, star-forming void dwarf galaxies and 89 blue, star-forming dwarf galaxies in more dense regions using spectroscopic observations from the Sloan Digital Sky Survey Data Release 7, as reprocessed in the MPA-JHU value-added catalog. We find very little difference between the two sets of galaxies, indicating little influence from the large-scale environment on their chemical evolution. Of particular interest are a number of extremely metal-poor dwarf galaxies that are less prevalent in voids than in the denser regions. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 68 135 Dwarf galaxy properties
See also: II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009) V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012) J/AJ/119/32 : Survey of galaxies within nearby voids. II (Grogin+, 2000) J/A+A/448/955 : Abundances of emission galaxies in SDSS-DR3 (Izotov+, 2006) J/A+A/462/535 : Low-metallicity HII regions and galaxies (Yin+, 2007) J/AJ/144/16 : Optical & HI properties of galaxies in voids (Kreckel+, 2012) J/ApJ/765/140 : Stacked spectra of SDSS star forming galaxies (Andrews+, 2013) J/ApJS/208/10 : κ-distribution effects in HII regions (Dopita+, 2013) J/A+A/550/A115 : Oxygen abundances and properties of galaxies (Hughes+, 2013) J/A+A/559/A114 : Updated O3N2 and N2 abundance indicators (Marino+, 2013) http://www.sdss.org/ : SDSS home page http://wwwmpa.mpa-garching.mpg.de/SDSS/DR7/ : MPA-JHU for the SDSS-DR7 release Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 7 I7 --- Seq KIAS-VAGC galaxy index number (1) 9 A1 --- f_Seq [e] e = extreme low gas-phase metallicity (12+log(O/H)<7.6) galaxy; flag added by CDS according to table 3 11- 12 I2 h RAh Hour of Right Ascension (J2000) 14- 15 I2 min RAm Minute of Right Ascension (J2000) 17- 21 F5.2 s RAs Second of Right Ascension (J2000) 23 A1 --- DE- Sign of the Declination (J2000) 24- 25 I2 deg DEd Degree of Declination (J2000) 27- 28 I2 arcmin DEm Arcminute of Declination (J2000) 30- 34 F5.2 arcsec DEs Arcsecond of Declination (J2000) 36- 41 F6.4 --- zsp [0.02/0.03] Spectroscopic redshift 43- 48 F6.2 mag rMag [-17/-16.3] Absolute r band magnitude 50- 53 F4.2 [-] O/H [7/8.6] The 12+log(O/H) abundance (2) 55- 58 F4.2 [-] e_O/H [0/0.7] Uncertainty in O/H 60- 68 A9 --- Loc Location code (3)
Note (1): The flux values for all required emission lines can be found in the MPA-JHU value-added catalog. Note (2): Metallicity values are calculated using the Direct Te method, with error estimates via a Monte Carlo method. Note (3): The void catalog of Pan et al. (2012MNRAS.421..926P) is used to classify the galaxies as either Void or Wall. If a galaxy is located too close to the boundary of the SDSS survey to identify whether or not it is inside a void, it is labeled as Uncertain. Among the 21 extremely metal-poor galaxies, four are located in voids (about 10% of the void dwarf population measured) and seventeen are in more dense regions (about 19% of the wall dwarf population measured); thus, there does not seem to be a special population of extreme low-metallicity galaxies in voids. Further study of these galaxies is recommended, to confirm metallicity values and identify any shared characteristics.
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Jul-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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