We present mid infrared (Mid-IR) spectra of the Compton-thick Seyfert 2 galaxy NGC,3281, obtained with the Thermal-Region Camera Spectrograph (T-ReCS) at the Gemini South telescope. The spectra present a very deep silicate absorption at 9.7,$mu$m, and [S{sc,iv]},10.5,$mu$m and [Ne{sc,ii]},12.7,$mu$m ionic lines, but no evidence of PAH emission. We find that the nuclear optical extinction is in the range 24 $leq$ A$_{V}$ $leq$ 83,mag. A temperature T = 300,K was found for the black-body dust continuum component of the unresolved 65,pc nucleus and at 130,pc SE, while the region at 130,pc reveals a colder temperature (200,K). We describe the nuclear spectrum of NGC,3281 using a clumpy torus model that suggests that the nucleus of this galaxy hosts a dusty toroidal structure. According to this model, the ratio between the inner and outer radius of the torus in NGC,3281 is $R_0/R_d$ = 20, with {bf 14} clouds in the equatorial radius with optical depth of $tau_{V}$ = 40,mag. We would be looking in the direction of the torus equatorial radius ($i$ = {bf 60$^{circ}$}), which has outer radius of R$_{0},sim$ 11,pc. The column density is N$_{H}approx$,{bf 1.2},$times,10^{24},cm^{-2}$ and iron K$alpha$ equivalent width ($approx$ 0.5 - 1.2,keV) are used to check the torus geometry. Our findings indicate that the X-ray absorbing column density, which classifies NGC,3281 as a Compton-thick source, may also be responsible for the absorption at 9.7,$mu$m providing strong evidence that the silicate dust responsible for this absorption can be located in the AGN torus.
تحميل البحث