  Extreme emission line galaxies (EELGs) are a notable galaxy genus, ultimately
being regarded as local prototypes of early galaxies at the cosmic noon. Robust
characterisation of their stellar content, however, is hindered by the
exceptionally high nebular emission present in their optical spectroscopic
data. This study is dedicated into recovering the stellar properties of a
sample of 414 EELGs as observed by the SDSS Survey. Such is achieved by means
of the spectral synthesis code FADO, which self-consistently considers the
stellar and nebular emission in an optical spectrum. Additionally, a
comparative analysis was carried on, by further processing the EELGs sample
with the purely stellar spectral synthesis code Starlight, and by extending the
analysis to a sample of 697 normal star-forming galaxies, expected to be less
affected by nebular contribution. We find that, for both galaxy samples,
stellar mass and mean age estimates by Starlight are systematically biased
towards higher values, and that an adequate determination of the physical and
evolutionary properties of EELGs via spectral synthesis is only possible when
nebular continuum emission is taken into account. Moreover, the differences
between the two population synthesis codes can be ascribed to the degree of
star-formation activity through the specific star-formation rate and the sum of
the flux of the most prominent emission lines. As expected, on the basis of the
theoretical framework, our results emphasise the importance of considering the
nebular emission while performing spectral synthesis, even for galaxies hosting
typical levels of star-formation activity.
