Low-Luminosity Active Galactic Nuclei

摘要: I review the basic properties of low-luminosity active galactic nuclei (LLAGNs) — objects in which activity similar to, but intrinsically milder than, that QSOs and luminous Seyferts is believed to be present. Until recently, most LLAGNs were first recognized as such studied at optical wavelengths, evidence for valuable information concerning its nature are now also being obtained many other spectral ranges. Low-ionization nuclear emission-line regions (LINERs) common LLAGNs; a large fraction them emission lines come from clouds gas probably photoionized by nonstellar continuum, rather than heated shocks. It clear, however, there could substantial heterogeneity among LINERs, particularly those with extended emission; some may produced cooling flows, supernova-driven winds, galaxy interactions or mergers. can easily hidden sight variety ways, including obscuration circumnuclear disks dilution bursts star formation. Direct imaging, spectroscopy, spectropolarimetry used isolate different components, especially high spatial and/or resolution. A surprising result Seyfert sometimes found dwarf very late-type galaxies. The nearby Sd III-IV NGC 4395 contains faintest known 1 nucleus, broad Ha luminosity only ∼ 0.1 M81. idea apparent “activity” galaxies direct consequence vigorous formation has strong supporting evidence, should seriously considered. As an example, focus on peculiar supernova 1987F, whose spectrum bears striking resemblance typical nuclei.