WARM IRAS SOURCES FROM THE POINT-SOURCE CATALOG .3. EMISSION-LINE PROPERTIES, CORRELATIONS, AND AGN UNIFIED MODELS

We consider correlations between emission-line properties and infrared parameters for 221 emission-line AGN associated with ''warm'' sources from the IRAS Point Source Catalog. Our analysis includes properties directly associated with the IR-emitting dust component as well as tes ts of geometric orientation schemes for unifying broad- and narrow-lin e AGN. The narrow-line reddening (from Halpha/Hbeta) and ionization le vel (from [O III]/Hbeta and [N II]/Halpha) are both correlated with th e parameters characterising the mid-IR emission. This is consistent wi th a model in which the mid-IR emission is produced partially by dust located within the narrow-line region, perhaps within the emission-lin e filaments themselves. Since this sample is selected using a (nominal ly) isotropic property, we may examine the popular hypothesis that bro ad-line and narrow-line objects differ primarily in their observed ori entation. The relative [O III] and IR luminosities of these two classe s show very similar distributions, strengthening the case for a unifie d classification. However, Fe II emission depends as much on far-IR sp ectral shape as on relative IR loudness, in contrast to earlier claims from small numbers of anomalous AGNs from the IRAS survey. This may b e accomodated under geometrically unified schemes only if the scale of the Fe II region is of the same order as that of structure in the war mest dust zone and if its geometry differs from that of the region emi tting, for example, broad Balmer lines. Line-width similarities make t his difficult to accomodate in a simple picture, suggesting that Fe II emission is linked to some intrinsic property of certain AGN. The sma ll number of very luminous narrow-line objects (''QSO 2'') has suggest ed a luminosity dependence of the covering fraction of the obscuring m aterial. We examine this by comparing the emission-line and IR luminos ities of these AGN. As shown by this ratio, the covering factor of dus t shows large scatter with the mean actually increasing toward higher luminosities. There is substantial overlap between broad- and narrow-l ine objects at all luminosities, with some Seyfert 2 galaxies having l arger dust covering than any broad-line objects. This scatter overwhel ms any overall trends that could account for the paucity of luminous n arrow-line objects.