Mid-Infrared Ne Ionic Lines Survey of Active Galaxies

scientific abstract we propose to observe a set of ne lines at various ionization stages from infrared luminous galaxies to reveal the origin of their luminosity and their evolutionary sequence. the iras mission revealed a new population of galaxies, infrared luminous galaxies, which are up to 100 time more luminous in the farir than in the optical band, are radiating more than 10^12 solar luminosity in the farir, and are comparable to quasars in their luminosity. strong optical line emission emanating from their nuclei suggests two kinds of ionizing sources: (1) active galactic nuclei (agn) and (2) huge starburst activity. since these activities are deeply buried within a huge amount of molecular gas, their direct observations are impossible in the optical band. hence the true origin of the luminosity of infrared luminous galaxies is still a mystery. one of the most promising way to discern agns from starburst and to reveal the origin of the huge luminosity will be through infraredfine structure line observations, since (1) there are various kinds of lines at various ionization stages in the infrared, and (2) the infrared lines can penetrate deep into the dustrich infrared luminous galaxies. for this purpose, we selected a set of ne lines at various stages of ionization. agn activities are definitely required to excite highly ionized lines, while low ionization lines will trace starburst activities. hence the intensity ratios of the lines at various stages of ionization will reveal the relative importance of agns and starbursts. by revealing the relative importance of agns and starbursts activities in various kinds of infrared luminous galaxies, we can test a hypothesis in which quasars evolved from infrared luminous galaxies and, during the evolutionary sequence, the dominant energy sources shift from starburst to agns. observation summary we propose to observe 13 galaxies for the autumn launch and tru [truncated!, Please see actual data for full text]