Sturm, E. and Rupke, D. and Contursi, A. and Kim, D. -C. and Lutz, D. and Netzer, H. and Veilleux, S. and Genzel, R. and Lehnert, M. and Tacconi, L. J. and Maoz, D. and Mazzarella, J. and Lord, S. and Sanders, D. and Sternberg, A. (2006) Mid-Infrared Diagnostics of LINERS. Astrophysical Journal Letters, 653 (1). L13-L16. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20110630-112733668
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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 emission-line 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.
|Additional Information:||© 2006 American Astronomical Society. Received 2006 July 11; accepted 2006 October 24; published 2006 November 27. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. A. S. and H. N. thank the Israel Science Foundation for support grants 221/03 and 232/03. H. N. acknowledges support by the Humboldt Foundation and thanks the host institution MPE.|
|Subject Keywords:||galaxies: active; infrared: galaxies|
|Official Citation:||Mid-Infrared Diagnostics of LINERS E. Sturm et al 2006 ApJ 653 L13|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||30 Jun 2011 22:31|
|Last Modified:||26 Dec 2012 13:21|
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