| Authors : | Subhashree Swain, Indian Institute of Astrophysics, Koramangala, Bangalore 560034, India
K.V.P. Lata, Department of Physics, Pondicherry University, Puducherry 605014, India
P. Shalima, Manipal Centre for Natural Sciences, Centre of Excellence, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India |
| Abstract : | We focuses on hot dust modeling in AGN NGC 4151 and analyzed the dust sublimation zone, considering the accretion disk as the primary emission. We have used SKIRT code, a 3D radiative transfer code to model the dust emission of the NGC 4151 AGN. In order to explain the observed IR SED of NGC 4151, we considered two models. The first model is the ’Torus Only’ model (TO model hereafter), which consists only of a torus geometry consisting of ISM dust. The second model is the ’Ring and Torus’ model (RAT model hereafter), composed of a ring of large graphite dust with sizes 0.1 - 1 μm, which is incorporated between the torus and dust free BLR. We vary the inclination angle (i), inner radius (of the torus and the ring, Rin,t and Rin,r, respectively), torus half-opening angle (σ), optical depth (τ9.7,t of the torus and τ9.7,r of the ring), and the dust clump size (Rclump). We perform a statistical analysis of the parameter space and find that all models can explain the flat NIR SED of NGC 4151 with only minor variations in the derived parameters. For the TO model, we get Rin,t = 0.1 pc, σ = 30°, i = 53°, τ_9.7,t = 10, and the clump size, Rclump = 0.4 pc. For the smooth RAT model, Rin,r = 0.04 pc and τ_9.7,total = 11 and for the clumpy RAT model, Rin,r = 0.04 pc/0.06 pc and τ9.7,total=20. The Rin,t from the TO model disagrees with the NIR observations (∼0.04 pc). Hence, the most likely scenario is that a hot graphite ring is located at a distance of 0.04 pc from the centre, composed of a smooth/clumpy distribution of dust followed by a dusty torus at 0.1 pc with an interstellar medium type of grains. |
