Luminosity–metallicity relation. The data point of the dwarf galaxy candidate is represented by the orange star. The data of Richer & McCall (1995) of dwarf irregular galaxies (dIs) are shown as red squares. The fit to that data by Richer & McCall (1995) is shown as the red line. The relation of the data of blue compact dwarfs (BCDs, blue triangles) is from Zhao et al. (2010). The data of TDGs from Duc & Mirabel (1999) are represented as dark circles, and the data from Weilbacher et al. (2003) as green diamonds.