New diagnostic methods for emission-line galaxies in deep surveys

Abstract

We present new quantitative classification methods for emission-line galaxies, which are specially designed to be used in deep galaxy redshift surveys. A good segregation between starbursts and active galactic nuclei, i.e. Seyfert 2s and LINERs, is obtained from diagnostic diagrams involving the [O II]λ3727 Å, [Ne III]λ3869 Å, Hβ and [O III]λ5007 Å relative intensities or the [O II]λ3727 Å and Hβ equivalent widths. Furthermore, the colour index of the continuum underlying [O II]λ3727 Å and Hβ provides an additional separation parameter between the two types of emission-line galaxies. We have applied the equivalent widths method to the 0