Spectral properties of AGN with very weak [O III] lines

The spectral properties of a sample of 58 Active Galactic Nuclei (AGN) spectra, in which emission [O III] ??4959, 5007 ? lines are weak or totally absent, are analyzed. In order to investigate the physical reason for the [O III] emission suppression, the spectral properties of the weak [O III] spectra sample are compared with the same properties of a sample of 269 spectra with the strong [O III] lines. The spectra are obtained from Sloan Digital Sky Survey (SDSS) Database. It is found that the objects with the weak or absent [O III] ??4959, 5007 ? lines generally have the high continuum luminosities (log(?L5100) > 45), that they are very rare at smaller redshifts (z < 0.3) and that they usually have strong starburst influence. From the sample with weak or absent [O III] lines, two boundary subgroups may be distinguished: the subgroup with a strong H? narrow component and subgroup with a very weak or negligible H? narrow component. The physical causes for the [O III] lines suppressing are probably different in these two subgroups: the [O III] lines are absent in objects with strong narrow H? probably because of strong starburst (SB) activity, which produces high density of the gas, while in the objects with the negligible narrow H?, the reason for [O III] and narrow H? suppression may be a low covering factor. Analizirane su spektralne osobine uzorka od 58 aktivnih galaktickih jezgara (AGJ) u kojem su [O III]??4959, 5007 ? linije slabe ili potpuno odsutne. U cilju istrazivanja fizickog razloga slabe emisije [O III], spektralne osobine uzorka sa slabim [O III] linijama su uporedjene sa istim osobinama AGJ uzorka od 269 spektara sa znacajnom jacinom [O III] linija. Spektri su preuzeti iz Sloan Digital Sky Survey (SDSS) baze. Primeceno je da objekti sa slabim ili odsutnim [O III] ??4959, 5007 ? linijama uglavnom imaju visoke luminoznosti kontinuuma (log(?L5100) > 45), retko se nalaze na malim crvenim pomacima (z < 0.3) i uglavnom imaju jak uticaj regiona u kojima se intenzivno formiraju zvezde. U uzorku sa slabim [O III] linijama, mogu se izdvojiti dve granicne podgrupe: podgrupa sa jakom uskom H? komponentom i podgrupa sa vrlo slabom ili zanemarljivom uskom H? komponentom. Fizicki razlog slabe emisije [O III] linija u ova dva poduzorka je verovatno razlicit: [O III] linije su slabe u objektima sa jakom uskom H? verovatno zbog pojacane aktivnosti u regionima u kojima se intenzivno formiraju zvezde, sto povecava gustinu gasa, dok u objektima sa zanemarljivom us