High ionization winds in the narrow line region of active galactic nuclei

We study the distribution of the radial velocity difference between the [O III]λ5007 line and Hβ emission line in a sample of 187 Seyfert 1 and low-redshift quasars. We identify objects with large blue-shifts (which we call ‘outliers’), with shifts to the blue up to 1000 km s−1. While the occurrence of such large shifts between narrow lines poses a potential challenge to the accuracy of redshift determinations, we also show that outliers are relatively infrequent, and not randomly distributed across the range of optical spectral properties. Large blue shifts occur only in a particular section of the Eigenvector-1 diagram. We suggest that this phenomenon could be associated to a high ionization outflow originating in the active nucleus.