Dependence of the warm dust luminosity L_wd of the sample of ~1000 SDSS compact galaxies with reliably derived oxygen abundance on a) total luminosity L_tot within 0.1−22 μm and b) Hβ luminosity L(Hβ). Red and blue filled circles are for galaxies with EW(Hβ) ≥ 50 Å and EW(Hβ) < 50 Å, respectively. c) and d) Same as in a) and b) but for the entire sample of ~4000 SDSS compact star-forming galaxies. In all panels, black solid lines are fits to the data where L_wd is calculated by adopting β = 2. Green solid lines in b) and d) are one-to-one relations between warm dust luminosities and luminosities of ionising radiation L_ion~ 100L(Hβ).