Emission-line ratios for low-L (♢) and high-L (□) GRB hosts and explosion sites. Long GRBs, for which a SN search was not feasible, are shown as circles. Limits are donated by arrows. For comparison, the emission-line ratios are overlaid for a wide population of field galaxies from the SDSS DR9 (Ahn et al. 2012) sample as a density plot. Among these data, we selected those whose emission lines were detected at > 5σ c.l. The discerning line between star-formation and AGN-dominated galaxies is shown as a thick solid line and was taken from Kewley et al. (2001). The region of composite galaxies is encircled by the thick solid the thick dashed lines (Kauffmann et al. 2003). Evolutionary models, calculated by Dopita et al. (2006), that link emission-line regions at ages from 0.1 to 5 Myr (shown as dotted lines; ages: 0.1, 1, 2, 3, and 4 Myr with the youngest stellar populations having the highest [O iii]/Hβ line ratios) and different metallicities (shown as thin solid lines; Z = 0.05, 0.2, 0.5, 1.0, and 2.0 Z_⊙; metallicity increases from left to right) are displayed. Errors are shown, if available. In some cases these are smaller than the size of the respective plot symbol. Figure adapted from Christensen et al. (2008). References: Della Valle et al. (2006a): the SN-less GRB 060614; Christensen et al. (2008): 980425, Han et al. (2010): 990712, 020903, and 030329; Levesque et al. (2010a): 991208, 010921, 050826, and 070612; Levesque et al. (2010b): 020819B; Thöne et al. (2008): the SN-less GRB 060505; Wiersema et al. (2007): 060218; Krühler et al. (2012): 080605A; Vergani et al. (2011): 091127; Levesque et al. (2011): 100316D.