The effect of active galactic nuclei on the mid-infrared aromatic features

Aleksandar M. Diamond-Stanic, George H. Rieke

Research output: Contribution to journalArticlepeer-review

70 Scopus citations


We present Spitzer measurements of the aromatic (also known as polycyclic aromatic hydrocarbon) features for 35 Seyfert galaxies from the revised Shapley-Ames sample and find that the relative strengths of the features differ significantly from those observed in star-forming galaxies. Specifically, the features at 6.2, 7.7, and 8.6 μm are suppressed relative to the 11.3 μm feature in Seyferts. Furthermore, we find an anti-correlation between the L(7.7 μm)/L(11.3 μm) ratio and the strength of the rotational H2 emission, which traces shocked gas. This suggests that shocks suppress the short-wavelength features by modifying the structure of the aromatic molecules or destroying the smallest grains. Most Seyfert nuclei fall on the relationship between aromatic emission and [Ne ii] emission for star-forming galaxies, indicating that aromatic-based estimates of the star formation rate are generally reasonable in galaxies hosting active galactic nuclei. For the outliers from this relationship, which have small L(7.7 μm)/L(11.3 μm) ratios and strong H2 emission, the 11.3 μm feature still provides a valid measure of the star formation rate.

Original languageEnglish (US)
Pages (from-to)140-153
Number of pages14
JournalAstrophysical Journal
Issue number1
StatePublished - Nov 20 2010


  • Galaxies: ISM
  • Galaxies: active
  • Galaxies: nuclei
  • Galaxies: seyfert

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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