Light breeze in the local Universe
  We analyze a complete spectroscopic sample of galaxies ($\sim$600,000 ) drawn
from Sloan Digital Sky Survey (SDSS, DR7) to look for evidence of galactic
winds in the local Universe. We focus on the shape of the [OIII]$\lambda$5007
emission line as a tracer of ionizing gas outflows. We stack our spectra in a
fine grid of star formation rate (SFR) and stellar mass to analyze the
dependence of winds on the position of galaxies in the SFR versus mass diagram.
We do not find any significant evidence of broad and shifted
[OIII]$\lambda$5007 emission line which we interpret as no evidence of
outflowing ionized gas in the global population. We have also classified these
galaxies as star-forming or AGN dominated according to their position in the
standard BPT diagram. We show how the average [OIII]$\lambda$5007 profile
changes as function of nature of the dominant ionizing source. We find that in
the star-forming dominated source the oxygen line is symmetric and governed by
the gravitational potential well. The AGN or composite
AGN$\setminus$star-formation activity objects, in contrast, display a prominent
and asymmetric profile that can be well described by a broad gaussian component
that is blue-shifted from a narrow symmetric core. In particular, we find that
the blue wings of the average [OIII]$\lambda$5007 profiles are increasingly
prominent in the LINERs and Seyfert galaxies. We conclude that, in the
low-redshift Universe, "pure" star-formation activity does not seem capable of
driving ionized-gas outflows, while, the presence of optically selected AGN
seems to play a primary role to drive such winds. We discuss the implications
of these results for the role of the quenching mechanism in the present day
Universe.
