Physical Conditions in a Sample of Seyfert and Starburst galaxies
Abstract
Active galactic nuclei (AGN) are thought to harbor massive black holes (M_BH ≈ 10^6-10^8 M_⊙ surrounded by an accretion disk responsible for the enormous energy rates observed in their unresolved nuclei. Seyfert galaxies represent the most common type of AGN. Seyfert 1 galaxies have broad permitted (FWHM ≈ 1-5×10^3 km s^{-1} and narrow (FWHM ≈ 5×10^2 km s^{-1}) permitted and forbidden lines and Seyfert 2 galaxies have only narrow permitted and forbidden line emission. According to the unified model of active galaxies, Seyfert 1 and Seyfert 2 galaxies are intrinsically the same, with their differences attributed to viewing angle. In Seyfert 2 galaxies, our line of sight to the broad line region (BLR) and the central engine is obstructed by an optically thick dusty torus-like structure, while in Seyfert 1 galaxies, our line of sight is not obstructed by the torus, allowing a direct view of the central regions of the active galaxy. In this work, we use photoionization models to fit the observed ratios between high and low ionization mid-infrared emission lines to separate the relative contributions of the AGN and star formation in the host galaxy. Overall, we found that the observed mid-infrared spectra can be reproduce by a two zone model defined by a radiation- and matter-bounded component.
- Publication:
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Revista Mexicana de Astronomia y Astrofisica Conference Series
- Pub Date:
- October 2011
- Bibcode:
- 2011RMxAC..40...72M
- Keywords:
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- galaxies: active