NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-24 T15:07:04 PDT
Help | Comment | NED Home

For refcode 2003AJ....126...81A:
Retrieve 58 NED objects in this reference.
Please click here for ADS abstract

NED Abstract

Copyright by American Astronomical Society. Reproduced by permission
2003AJ....126...81A Spectral Energy Distributions of Seyfert Nuclei Almudena Alonso-Herrero, Alice C. Quillen, George H. Rieke, Valentin D. Ivanov, and Andreas Efstathiou Abstract. We present nuclear spectral energy distributions (SEDs) in the range 0.4 -- 16 microns for an expanded CfA sample of Seyfert galaxies. The spectral indexes (f_{nu}_ is proportional to {nu}^-{alpha}_IR_^) from 1 to 16 microns range from {alpha}_IR_~0.9 to 3.8. The shapes of the spectra are correlated with Seyfert type in the sense that steeper nuclear SEDs ({nu}f_{nu}_ increasing with increasing wavelength) tend to be found in Seyfert 2's, and flatter SEDs ({nu}f_{nu}_ is constant) in Seyfert 1 -- 1.5's. The galaxies optically classified as Seyferts 1.8's and 1.9's display values of {alpha}_IR_ as in type 1 objects, or values intermediate between those of Seyfert 1's and Seyfert 2's. The intermediate SEDs of many Seyfert 1.8 -- 1.9's may be consistent with the presence of a pure Seyfert 1 viewed through a moderate amount (A_V_<~5 mag) of foreground galaxy extinction. We find, however, that between 10% and 20% of galaxies with broad optical line components have steep infrared SEDs. Torus models usually adopt high equatorial opacities to reproduce the infrared properties of Seyfert 1's and 2's, resulting in a dichotomy of infrared SEDs (flat for type 1's, and steep for type 2's). Such a dichotomy, however, is not observed in our sample. The wide range of spectral indexes observed in the type 2 objects, the lack of extremely steep SEDs, and the large numbers of objects with intermediate spectral indexes cannot be reconciled with predictions from existing optically thick torus models. We discuss possible modifications to improve torus models, including low optical depth tori, clumpy dusty tori, and high optical depth tori with an extended optically thin component. Keywords: Galaxies: Active, Galaxies: Nuclei, Galaxies: Photometry, Galaxies: Seyfert, Infrared Radiation
Retrieve 58 NED objects in this reference.
Please click here for ADS abstract

Back to NED Home