X-rays as the dominant excitation mechanism of [Fe II] and H2 emission lines in active galaxies

OLI L. DORS; ROGEMAR A. RIFFEL; MÓNICA V. CARDACI; GUILLERMO F. HÄGELE; ÂNGELA C. KRABBE; ENRIQUE PÉREZ-MONTERO; IRAPUAN RODRIGUES

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2012 vol. 422 p. 252 - 260

0035-8711

We investigate the excitation mechanisms of near-infrared [Fe II] and H2 emission lines observed in active galactic nuclei (AGNs). We built a photoionization model grid considering a two-component continuum: one component accounts for the `big bump´ component peaking at 1Ryd and another represents the X-ray source that dominates the continuum emission at high energies. Photoionization models considering as ionizing source a spectral energy distribution obtained from photometric data of Seyfert 2 Mrk 1066 taken from the literature were considered. Results of these models were compared with a large sample of observational long-slit and Integral field Unit (IFU) spectroscopy data of the nuclear region for a sample of active objects. We found that the correlation between the observational [Fe II] lambda 1.2570μm/Pa beta and H2 lambda 2.1218μm/Brγ is well reproduced by our models, as are the relationships that involve the H2 emission-line ratios observed in the spectroscopic data. We conclude that heating by X-rays produced by active nuclei can be considered a common and very important mechanism of excitation of [Fe II] and H2.