ESO 146–G14, a retarded disc galaxy

Abstract
In our search for nearby young and unevolved galaxies we encountered ESO 146–G14, a blue low-surface-brightness late-type disc galaxy with remarkable properties. The analysis of the chemical abundances of the brightest HII regions yields an oxygen abundance of 6±1 per cent of the solar value, which is low even in comparison with most metal-poor blue compact dwarf galaxies. We determine a dynamical mass of 7±×109 M of which ∼ 40 per cent is in HI. Optical/near-IR observations in combination with spectral evolutionary models are used to derive information about the star formation history. Two models give good fits to the data. One has a very low age (∼108 yr), a steep mass function and a high star formation rate. This solution seems marginally incompatible with the dynamical time-scale. We favour a model that has a Salpeter initial mass function (IMF), an age of 9±2 Gyr and a low mean star formation rate. We argue that ESO 146–G14 belongs to a population of unevolved galaxies, many of which are likely to have a surface brightness below the optical detection limit.

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