NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-16 T08:11:56 PDT
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For refcode 2005MNRAS.364.1041R:
Retrieve 31 NED objects in this reference.
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NED Abstract

Copyright by Royal Astronomical Society. 2005MNRAS.364.1041R Molecular hydrogen and [FeII] in active galactic nuclei - II. Results for Seyfert 2 galaxies Rodriguez-Ardila, A.; Riffel, R.; Pastoriza, M. G. Abstract. Near-infrared spectroscopy is used to study the kinematics and excitation mechanisms of H_2_ and [FeII] lines in a sample dominated by Seyfert 2 galaxies. The spectra simultaneously cover the JHK bands, allowing us to compare line fluxes emitted in the interval 0.8-2.4 microns and avoiding aperture and seeing effects. The H_2_ lines are systematically narrower than the narrow-line region lines, suggesting that, very likely, the H_2_ does not originate from the same parcel of gas that forms the narrow-line region. Emission-line ratios between H_2_ lines favour thermal excitation mechanisms for the molecular gas in active galactic nuclei. It was found that non-thermal excitation contributes, at most, 30 per cent of the observed H_2_. Thermal excitation is also confirmed by the rather similar vibrational and rotational temperatures in the objects (~2000 K). The mass of hot H_2_ ranges from 10^2^ to 10^3^M_sun_, with nearly half of objects showing values of <500 M_sun_. It shows that the fraction of molecular mass present in the nuclear region and emitting in the near-infrared is a very small fraction of the warm molecular mass present in the centre. A diagnostic diagram composed of the line ratios H_2_/Br{gamma} and [FeII]/Pa{beta} proves to be a useful tool in the near-infrared for separating emission-line objects by their degree of nuclear activity. We found that active galactic nuclei are characterized by H_2_ 2.121 microns/Br{gamma} and [FeII] 1.257 microns/Pa{beta} flux ratios between 0.6 and 2. Starburst/HII galaxies display line ratios <0.6 while low-ionization nuclear emission-line regions are characterized by values larger than 2 in either ratio.
Retrieve 31 NED objects in this reference.
Please click here for ADS abstract

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