HII regions in CALIFA survey: II. The relation between their physical
  properties and galaxy evolution
  We present in here the exploration of the physical properties of the sample
of HII regions and aggregations of the last HII regions catalog of the CALIFA
survey. This sample comprises the optical spectroscopic properties of more than
~26,000 ionized regions corresponding to 924 galaxies from the Integral Field
Spectroscopy data, including the flux intensity and equivalent widths and the
properties of their underlying stellar population. In the current study we
derive a set of physical quantities for all these regions based on those
properties, including (i) the fraction of young stars; (ii) the ionization
strength (using six different estimations); (iii) the oxygen abundance (using
25 different calibrators); (iv) the nitrogen and nitrogen-to-oxygen abundance;
(v) the dust extinction and (vi) the electron density. Using this dataset we
explore how the loci in the classical diagnostic diagrams are connected with
those quantities, the radial distributions of these parameters, and the
inter-relations between themselves and with the properties of the underlying
stellar populations. We conclude that many properties of the HII regions are
tightly related to the galactic stellar evolution at the location where those
regions are observed. Those properties are modulated only as a second-order
effect by the properties of the ionizing stars and the ionized nebulae that do
not depend on the astrophysical context in which they are formed. Our results
highlight the importance of HII regions to explore the chemical evolution in
galaxies, clarifying which of their properties can be used as proxies of that
evolution.
