a) Dependence of the warm dust mass M_wd to the young stellar population mass M_y ratio on the Hβ equivalent width EW(Hβ) for the sample of ~1000 SDSS compact galaxies with a reliably derived oxygen abundance. b) Same as in a) but for the entire sample of ~4000 SDSS compact star-forming galaxies. In both panels, the warm dust mass M_wd is calculated by adopting β = 2. Solid lines are quadratic fits to the data, while dashed and dotted lines correspond to M_wd/M_y ratios, which are proportional to the luminosity L_ion of ionising radiation and total luminosity L_tot, respectively.