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Eigenvector 1 (EV1) is the formal parameter which allows the introduction ofsome order in the properties of the unobscured type 1 active galaxies. We aimto understand the nature of this parameter by analyzing the most extremeexamples of quasars with the highest possible values of the correspondingeigenvalues $R_{Fe}$. We selected the appropriate sources from the SloanDigital Sky Survey (SDSS) and performed detailed modeling, including varioustemplates for the Fe II pseudo-continuum and the starlight contribution to thespectrum. Out of 27 sources with $R_{Fe}$ larger than 1.3 and with themeasurement errors smaller than 20\% selected from the SDSS quasar catalog,only six sources were confirmed to have a high value of $R_{Fe}$, defined asbeing above 1.3. All other sources have $an R_{Fe}$ of approximately 1. Threeof the high $R_{Fe}$ objects have a very narrow H$\beta$ line, below 2100 kms$^{-1}$ but three sources have broad lines, above 4500 km s$^{-1}$, that donot seem to form a uniform group, differing considerably in black hole mass andEddington ratio; they simply have a very similar EW([OIII]5007) line.Therefore, the interpretation of the EV1 remains an open issue.

The properties of active galaxies at the extreme of eigenvector 1