Journal Article

X-rays as the dominant excitation mechanism of [Fe <span class="smallCaps">ii</span>] and H<sub>2</sub> emission lines in active galaxies

Oli L. Dors, Rogemar A. Riffel, Mónica V. Cardaci, Guillermo F. Hägele, Ângela C. Krabbe, Enrique Pérez-Montero and Irapuan Rodrigues

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 422, issue 1, pages 252-260
Published in print May 2012 | ISSN: 0035-8711
Published online April 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.20600.x
X-rays as the dominant excitation mechanism of [Fe ii] and H2 emission lines in active galaxies

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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 1 Ryd 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 Seyert 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]λ 1.2570 μm/Paβ and m/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.

Keywords: galaxies: ISM; galaxies: Seyfert; infrared: galaxies

Journal Article.  5895 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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