High z Low Z Galaxies

From Salzer et al. (arXiv:0903.3948). Caption reads: Luminosity-metallicity relation for 1300+ low-z KISS galaxies (z < 0.095; small dots) and the 13 [O III]-detected star-forming
KISS galaxies (red squares). The solid line is a linear fit to the low-z galaxies, while the lower dashed line has the same slope but fits the higher-z galaxies with an offset of -1.1 dex.

These galaxies have redshifts in the range 0.29-0.42. Such luminous galaxies at such low metallicities pose problems for galaxy evolution models, as the evolution in metallicity at these redshifts is expected to be mild.