Mid-infrared diagnostics of LINERs

作者：Sturm E^*; Rupke D; Contursi A; Kim D C; Lutz D; Netzer H; Veilleux S; Genzel R; Lehnert M; Tacconi L J; Maoz D; Mazzarella J; Lord S; Sanders D; Sternberg A

来源：Astrophysical Journal, 2006, 653(1): L13-L16.

DOI：10.1086/510381

• galaxies : active
• infrared : galaxies

We report results from the first mid-infrared spectroscopic study of a comprehensive sample of 33 LINERS, observed with the Spitzer Space Telescope. We compare the properties of two different LINER populations: infrared-faint LINERS, with LINER emission arising mostly in compact nuclear regions, and infrared-luminous LINERS, which often show spatially extended (non-AGN) LINER emission. We show that these two populations can be easily distinguished by their mid-infrared spectra in three different ways: (1) their mid-IR spectral energy distributions (SEDs), (2) the emission features of polycyclic aromatic hydrocarbons (PAHs), and (3) various combinations of IR fine-structure line ratios. IR-luminous LINERs show mid-IR SEDs typical of starburst galaxies, while the mid-IR SEDs of IR-faint LINERS are much bluer. PAH flux ratios are significantly different in the two groups. Fine-structure emission lines from highly excited gas, such as [O IV], are detected in both populations, suggesting the presence of an additional AGN in a large fraction of IR-bright LINERs as well, which contributes little to the combined mid-IR light. The two LINER groups occupy different regions of mid-infrared emissionline excitation diagrams. The positions of the various LINER types in our diagnostic diagrams provide important clues regarding the power source of each LINER type. Most of these mid-infrared diagnostics can be applied at low spectral resolution, making AGN- and starburst-excited LINERs distinguishable at high redshifts as well.

• 出版日期2006-12-10