Aperture-free star formation rate of SDSS star-forming galaxies
  Large area surveys with a high number of galaxies observed have undoubtedly
marked a milestone in the understanding of several properties of galaxies, such
as star-formation history, morphology, and metallicity. However, in many cases,
these surveys provide fluxes from fixed small apertures (e.g. fibre), which
cover a scant fraction of the galaxy, compelling us to use aperture corrections
to study the global properties of galaxies. In this work, we derive the current
total star formation rate (SFR) of Sloan Digital Sky Survey (SDSS) star-forming
galaxies, using an empirically based aperture correction of the measured $\rm
H\alpha$ flux for the first time, thus minimising the uncertainties associated
with reduced apertures. All the $\rm H\alpha$ fluxes have been
extinction-corrected using the $\rm H\alpha/H\beta$ ratio free from aperture
effects. The total SFR for $\sim$210,000 SDSS star-forming galaxies has been
derived applying pure empirical $\rm H\alpha$ and $\rm H\alpha/H\beta$ aperture
corrections based on the Calar Alto Legacy Integral Field Area (CALIFA) survey.
We find that, on average, the aperture-corrected SFR is $\sim$0.65dex higher
than the SDSS fibre-based SFR. The relation between the SFR and stellar mass
for SDSS star-forming galaxies (SFR--$\rm M_\star$) has been obtained, together
with its dependence on extinction and $\rm H\alpha$ equivalent width. We
compare our results with those obtained in previous works and examine the
behaviour of the derived SFR in six redshift bins, over the redshift range $\rm
0.005 \leq z\leq 0.22$. The SFR--$\rm M_\star$ sequence derived here is in
agreement with selected observational studies based on integral field
spectroscopy of individual galaxies as well as with the predictions of recent
theoretical models of disc galaxies.
