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

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 Seyert 2 Mrk1066 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 1.2570μm/Paβ and H2λ2.1218μm/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.Facultad de Ciencias Astronómicas y Geofísica

Optical and mid-infrared neon abundance determinations in star-forming regions

We have used observational spectroscopic data of star-forming regions compiled from the literature and photoionization models to analyse the neon ionic abundances obtained using both optical and mid-infrared emission lines. Comparing Ne++/H+ ionic abundances from distinct methods, we have found that, on average, the abundances obtained via infrared emission lines are higher than those obtained via optical lines, by a factor of 4. Photoionization models with abundance variations along the radius of the hypothetical nebula provide a possible explanation for a large part of the difference between ionic abundances via optical and infrared emission lines. The ionization correction factor (ICF) for the neon is obtained from direct determinations of ionic fractions using infrared emission lines. We derive a constant Ne/O ratio (log Ne/O ≈ -0.70) for a large range of metallicities, independently of the ICF used to compute the neon total abundance.Facultad de Ciencias Astronómicas y Geofísica

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

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 Seyert 2 Mrk1066 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 1.2570μm/Paβ and H2λ2.1218μm/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.Facultad de Ciencias Astronómicas y Geofísica

Optical and mid-infrared neon abundance determinations in star-forming regions

We have used observational spectroscopic data of star-forming regions compiled from the literature and photoionization models to analyse the neon ionic abundances obtained using both optical and mid-infrared emission lines. Comparing Ne++/H+ ionic abundances from distinct methods, we have found that, on average, the abundances obtained via infrared emission lines are higher than those obtained via optical lines, by a factor of 4. Photoionization models with abundance variations along the radius of the hypothetical nebula provide a possible explanation for a large part of the difference between ionic abundances via optical and infrared emission lines. The ionization correction factor (ICF) for the neon is obtained from direct determinations of ionic fractions using infrared emission lines. We derive a constant Ne/O ratio (log Ne/O ≈ -0.70) for a large range of metallicities, independently of the ICF used to compute the neon total abundance.Facultad de Ciencias Astronómicas y Geofísica