The Nature of Ionized Gas in Giant Elliptical Galaxies

摘要: I review the current understanding of origin and nature ``warm'' ionized gas in giant elliptical galaxies light results recent imaging spectroscopic surveys. CCD surveys have revealed that emission-line disks or filaments are (as a rule) associated with dust absorption, even X-ray brightest systems. This strongly suggests this is generally not through ``cooling flows''; galaxy interactions favored instead. Using data from new spectrophotometric survey ``normal'' covering whole optical range, extended ellipticals found to be --without exception-- LINER class, most probably NOT powered by star formation activity. discuss two independent pieces evidence which suggest means distributed source ionization: (i) A significant correlation exists between H-alpha+[NII]luminosity luminosity within region occupied gas, (ii) ionization parameter does change significantly galactocentric radius. Two potential sources evaluated: Photoionization old hot stars (of post-AGB and/or AGB-Manque' type) mechanical energy flux electron conduction hot, X-ray-emitting gas.