Astrophys. J., 782, 35 (2014/February-2)
Choirs H I galaxy groups: the metallicity of dwarf galaxies.
SWEET S.M., DRINKWATER M.J., MEURER G., BEKKI K., DOPITA M.A., KILBORN V. and NICHOLLS D.C.
Abstract (from CDS):
We present a recalibration of the luminosity-metallicity relation for gas-rich, star-forming dwarfs to magnitudes as faint as MR∼ -13. We use the Dopita et al. metallicity calibrations to calibrate the relation for all the data in this analysis. In metallicity-luminosity space, we find two subpopulations within a sample of high-confidence Sloan Digital Sky Survey (SDSS) DR8 star-forming galaxies: 52% are metal-rich giants and 48% are metal-medium galaxies. Metal-rich dwarfs classified as tidal dwarf galaxy (TDG) candidates in the literature are typically of metallicity 12 + log(O/H) = 8.70±0.05, while SDSS dwarfs fainter than MR= -16 have a mean metallicity of 12 + log(O/H) = 8.28±0.10, regardless of their luminosity, indicating that there is an approximate floor to the metallicity of low-luminosity galaxies. Our hydrodynamical simulations predict that TDGs should have metallicities elevated above the normal luminosity-metallicity relation. Metallicity can therefore be a useful diagnostic for identifying TDG candidate populations in the absence of tidal tails. At magnitudes brighter than MR∼ -16, our sample of 53 star-forming galaxies in 9 H I gas-rich groups is consistent with the normal relation defined by the SDSS sample. At fainter magnitudes, there is an increase in dispersion of the metallicity of our sample, suggestive of a wide range of H I content and environment. In our sample, we identify three (16% of dwarfs) strong TDG candidates (12 + log(O/H) > 8.6) and four (21%) very metal-poor dwarfs (12 + log(O/H) < 8.0), which are likely gas-rich dwarfs with recently ignited star formation.
galaxies: abundances - galaxies: dwarf - galaxies: formation - galaxies: groups: general - galaxies: star formation - techniques: spectroscopic
erratum vol. 786, art. 75 (2014)
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