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Mid-Infrared Spectra of Classical AGNs Observed with the Spitzer Space Telescope
The Astrophysical Journal (2005)
  • D. W. Weedman, Cornell University
  • Lei Hao, Cornell University
  • Sarah J.U. Higdon, Cornell University
  • D. Devost, Cornell University
  • Yanling Wu, Cornell University
  • V. Charmandaris, Cornell University
  • B. R. Brandl, Leiden Observatory
  • E. Bass, Cornell University
  • J. R. Houck, Cornell University
Full low-resolution (65 < R < 130) and high-resolution (R  600) spectra between 5 and 37 m obtained with the Infrared Spectrograph ( IRS) on the Spitzer Space Telescope are presented for eight classical active galactic nuclei (AGNs) that have been extensively studied previously. Spectra of these AGNs are presented as comparison standards for the many objects, including sources at high redshift, that are being observed spectroscopically in the mid-infrared for the first time using the IRS. The AGNs are NGC 4151, Mrk 3, I Zw 1, NGC 1275, Centaurus A, NGC 7469, Mrk 231, and NGC 3079. These sources are used to demonstrate the range of infrared spectra encountered in objects that have widely different classification criteria at other wavelengths but that unquestionably contain AGNs. Overall spectral characteristics, including continuum shape, nebular emission lines, silicate absorption and emission features, and PAH emission features, are considered to understand how spectral classifications based on mid-infrared spectra relate to those previously derived from optical spectra. The AGNs are also compared to the same parameters for starburst galaxies such as NGC 7714 and the compact, low-metallicity starburst SBS 0335052 previously observed with the IRS. Results confirm the much lower strengths of PAH emission features in AGNs, but there are no spectral parameters in this sample that unambiguously distinguish AGNs and starbursts based only on the slopes of the continuous spectra. 
  • Galaxies,
  • Active,
  • Nuclei,
  • Starburst,
  • Infrared
Publication Date
November 10, 2005
Publisher Statement
This version of the paper was obtained from In order for the work to be deposited in, the author must have copyright or it must be available under the Creative Commons Attribution license,Creative Commons Attribution-Noncommercial-ShareAlike license, orCreate Commons Public Domain Declaration. The publisher's final edited version of this article will be available at The Astrophysical Journal.
Citation Information
D. W. Weedman, Lei Hao, Sarah J.U. Higdon, D. Devost, et al.. "Mid-Infrared Spectra of Classical AGNs Observed with the Spitzer Space Telescope" The Astrophysical Journal Vol. 633 Iss. 2 (2005) p. 706 - 716
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