Mid-IR properties of Seyferts: Spitzer/IRS spectroscopy of the IRAS
  12micron Seyfert sample
  We performed an analysis of the mid-infared properties of the 12micron
Seyfert sample, a complete unbiased 12micron flux limited sample of local
Seyfert galaxies selected from the IRAS Faint Source Catalog, based on low
resolution spectra obtained with the Infrared Spectrograph (IRS) on-board
Spitzer Space Telescope. A detailed presentation of this analysis is dicussed
in Wu et al. (2009).
  We find that on average, the 15-30micron slope of the continuum is
-0.85+/-0.61 for Seyfert 1s and -1.53+/-0.84 for Seyfert 2s, and there is
substantial scatter in each type. Moreover, nearly 32% of Seyfert 1s, and 9% of
Seyfert 2s, display a peak in the mid-infrared spectrum at 20micron, which is
attributed to an additional hot dust component. The Polycyclic Aromatic
Hydrocarbon (PAH) equivalent width decreases with increasing dust temperature,
as indicated by the global infrared color of the host galaxies. However, no
statistical difference in PAH equivalent width is detected between the two
Seyfert types, 1 and 2, of the same bolometric luminosity. Finally, we propose
a new method to estimate the AGN contribution to the integrated 12micron galaxy
emission, by subtracting the "star formation" component in the Seyfert
galaxies, making use of the tight correlation between PAH 11.2micron luminosity
and 12micron luminosity for star forming galaxies.
