A statistical study of SDSS radio-emitters
  The cross-correlation of the Sloan Digital Sky Survey Data Release 7 with the
Faint Images of the Radio Sky at Twenty-Centimeters survey allows for a
multiwavelength statistical study of radio-optical galaxy properties on a very
large number of sources. The correlation we find between $L_{[20
cm]}/L_{[H\alpha]}$ and optical emission line ratios suggests that the origin
of the emission in powerful radio-galaxies is of nuclear rather than of stellar
origin. In particular, the spectroscopic classification in Seyferts, Low
Ionization Narrow Emission Regions (LINERs) and star-forming galaxies provided
by emission-line diagnostic diagrams peaks on the AGN region for higher $L_{[20
cm]}/L_{[H\alpha]}$ values. The trend differs from Seyferts to LINERs. The
[NII]/H$\alpha$ vs. equivalent width of the H$\alpha$ line diagram confirms the
LINER classification for most of those that have been identified with the
traditional diagnostic diagrams. A small fraction of sources seem to be powered
by post-AGB stars instead.
