AN INFRARED EMISSION-LINE SEARCH FOR OBSCURED ACTIVE NUCLEI -- SURVEYING FOUR SUBSAMPLES OF THE STRONGEST CANDIDATES

one of the outstanding unanswered questions in extragalactic astronomy is the nature of the irluminous galaxies discovered by iras. these galaxies emit nearly all their power in the farir but their nuclei are so thoroughly enshrouded by dust that previous studies have failed to reveal the source of their quasarlevel luminosities. it is not known whether they contain heavily obscured nonstellar central engines or if their extraordinary luminosities are produced by stellar processes such as enormous bursts of star formation. this is of particular interest because they may dominate the space density of highluminosity objects in the universe, and therefore are being discovered at cosmologically significant distances. only spectroscopy at long wavelengths can penetrate the enormous extinctions present (av2040). whereas the core programs are observing several such galaxies in depth, here we take a complementary approach: a larger survey for the 2 strongest highionization forbidden lines emitted by seyfert nuclei, from our complete irfluxlimited sample of galaxies. the o iv26um and ne v14.3um lines are the most definitive indicators of photoionization by an obscured seyfert nucleus, and are not produced by o and b stars. neither line can be detected by any instrument other than iso. our sample was constructed using every available indicator of nonstellar nuclear activity that still works in the presence of heavy reddening: hot iras colors, extremely high ir luminosity, or strong radio or xray emission. we will search for hidden agns in each galaxy which meets these criteria, yet is not optically classified as a seyfert. our sample will be sufficiently large for the required statistical accuracy to determine the true space density of all agn typesfree from incompleteness due to dust obscurationfor the first time. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]