Integral field spectroscopy of a sample of nearby galaxies: II.
  Properties of the H ii regions
  In this work we analyze the spectroscopic properties of a large number of H
ii regions, \sim2600, located in 38 galaxies. The sample of galaxies has been
assembled from the face-on spirals in the PINGS survey and a sample described
in M\'armol-Queralt\'o (2011, henceforth Paper I). All the galaxies were
observed using Integral Field Spectroscopy with a similar setup, covering their
optical extension up to \sim2.4 effective radii within a wavelength range from
\sim3700 to \sim6900{\AA}. We develop a new automatic procedure to detect H ii
regions, based on the contrast of the H{\alpha} intensity maps. Once detected,
the procedure provides us with the integrated spectra of each individual
segmented region. A well-tested automatic decoupling procedure has been applied
to remove the underlying stellar population, deriving the main proper- ties of
the strongest emission lines in the considered wavelength range (covering from
[O ii] {\lambda}3727 to [S ii] {\lambda}6731). A final catalogue of the
spectroscopic properties of these regions has been created for each galaxy. In
the current study we focused on the understanding of the average properties of
the H ii regions and their radial distributions. We find that the gas-phase
oxygen abundance and the H{\alpha} equivalent width present negative and
positive gradient, respectively. The distribution of slopes is statistically
compatible with a random Gaussian distribution around the mean value, if the
radial distances are measured in units of the respective effective radius. No
difference in the slope is found for galaxies of different morphologies:
barred/non-barred, grand-design/flocculent. Therefore, the effective radius is
a universal scale length for gradients in the evolution of galaxies. Other
properties have a larger variance across each object.
