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Choirs HI galaxy groups: The metallicity of dwarf galaxies

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posted on 2024-07-26, 14:02 authored by Sarah Sweet, Michael J. Drinkwater, Gerhardt Meurer, Kenji Bekki, Michael A. Dopita, Virginia KilbornVirginia Kilborn, David C. Nicholls
We present a recalibration of the luminosity-metallicity relation for gas-rich, star-forming dwarfs to magnitudes as faint as M-R similar to -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 M-R = -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 havemetallicities 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 M-R similar to -16, our sample of 53 star-forming galaxies in 9 HI 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 HI 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.

Funding

National Aeronautics and Space Administration

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ISSN

1538-4357

Journal title

Astrophysical Journal

Volume

782

Issue

1

Article number

article no. 35

Pagination

11 pp

Publisher

Institute of Physics

Copyright statement

Copyright © 2014 The American Astronomical Society. The published version is reproduced in accordance with the copyright policy of the publisher and can be also be located at http://doi.org/10.1088/0004-637x/782/1/35.

Language

eng

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