Study of hidden mergers in double-peaked emission-line galaxies

Abstract

We present a study of double-peaked (DP) emission-line galaxies at z < 0:1 based on a subset of 84; 492 spectra extracted from the SDSS catalog. We have performed an automated selection procedure of DP spectra by adapting a previously existing routine developed for stars. A total of 5; 682 galaxies of the parent database have been found to exhibit a significant double peak in at least one of the four emission lines traditionally used in the Baldwin, Phillips and Terlevich (BPT) diagrams to discriminate among different ionization mechanisms. A preliminary investigation on the possible existence of an anti-correlation between the ratios of fluxes from the [OIII] λ 5007 line and velocity shifts of the red and blue components of the DP lines has produced results independent of the BPT classification of the galaxies. For most of the outliers of this relationship we find that the position of the strong [OIII] peak is significantly closer to the stellar velocity than for the weak [OIII] peak. These off-centered outliers could be linked to minor mergers in which central star formation has been enhanced or to objects with asymmetric gas out ows.