Single Star-forming galaxies and Star-forming galaxies in SF+SF and   mixed pairs
  We compare the SFR of single star-forming galaxies with the SFR of star-forming galaxies in pairs. Volume-limited samples are compared selected from the 2dFGRS, applying a maximum magnitude difference criterion. We show that SF galaxies in SF + SF pairs typically increase their SFR as they get fainter, whereas this does not happen for SF galaxies in mixed (SF + passive) pairs. And we provide evidence that differences between single SF and SF in pairs get more significant when SF galaxies in mixed pairs are excluded from the pair sample. Our analysis confirms that enhanced SFR and the presence of a companion galaxy (on 0.5 h^-1 Mpc scale) are correlated quantities, provided the galaxy is neither too luminous nor too faint, and the triggering galaxy is itself a SF galaxy. 
B. Kelm, P. Focardi