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Polycyclic aromatic hydrocarbon in the central region of the Seyfert 2 galaxy NGC 1808

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Polycyclic aromatic hydrocarbon in the central region of the Seyfert 2 galaxy NGC 1808

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Título Polycyclic aromatic hydrocarbon in the central region of the Seyfert 2 galaxy NGC 1808
Autor Sales, Dinalva Aires de
Pastoriza, Miriani Griselda
Riffel, Rogério
Winge, Claudia
Abstract We present mid-infrared spectra of the Seyfert 2 galaxy NGC 1808, obtained with the Gemini’s Thermal-Region Camera Spectrograph at a spatial resolution of ∼26 pc. The high spatial resolution allowed us to detect bright polycyclic aromatic hydrocarbons (PAHs) emissions at 8.6 and 11.3 μm in the galaxy centre (∼26 pc) up to a radius of 70 pc from the nucleus. The spectra also present [Ne II]12.8 μm ionic lines, and H2 S(2) 12.27 μm molecular gas line. We found that the PAHs profiles are similar to Peeters’s A class, with the line peak shifted towards the blue. The differences in the PAH line profiles also suggest that the molecules in the region located 26 pc north-east of the nucleus are more in the neutral than in the ionized state, while at 26 pc south-west of the nucleus, the molecules are mainly in ionized state. After removal of the underlying galaxy contribution, the nuclear spectrum can be represented by a Nenkova’s CLUMPY torus model, indicating that the nucleus of NGC 1808 hosts a dusty toroidal structure with an angular cloud distribution of σ = 70◦, observer’s view angle i = 90◦ and an outer radius of R0 ∼ 0.55 pc. The derived column density along the line of sight is NH = 1.5 × 1024 cm2, which is sufficient to block the hard radiation from the active nucleus, and would explain the presence of PAH molecules near to the NGC 1808’s active nucleus.
Contido em Monthly notices of the royal astronomical society. Oxford. Vol. 429, no. 3 (Mar. 2013), p. 2634-2642
Assunto Compostos orgânicos
Espectros astronômicos
Galaxias seyfert
Nucleo galatico
[en] Galaxies: seyfert
[en] Galaxies: starburst
[en] Infrared: ISM
[en] ISM: molecules
[en] Techniques: spectroscopic
Origem Estrangeiro
Tipo Artigo de periódico
URI http://hdl.handle.net/10183/94339
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