We performed an analysis of the mid-infared properties of the 12 \mu m Seyfert sample , a complete unbiased 12 \mu m 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 15-30 \mu m slope of the continuum is < \alpha _ { 15 - 30 } > =-0.85 \pm 0.61 for Seyfert 1s and -1.53 \pm 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 20 \mu m , 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 12 \mu m galaxy emission , by subtracting the ” star formation ” component in the Seyfert galaxies , making use of the tight correlation between PAH 11.2 \mu m luminosity and 12 \mu m luminosity for star forming galaxies .