Metallicity – gas fraction μ of SF dwarfs, assuming a closed box model (Lee et al. 2003). From the eight Abell TNG targets with available data, only three galaxies in Hercules agree this model, while the others do not. 2151–7583 (IC 1182:[S72] d) is the most evident outlier, known as a tidal dwarf candidate in interaction with IC1182 (Iglesias-Paramo et al. 2003; Petropoulou et al. 2011). The cross in the upper left shows typical uncertainties in the two parameters.