A NEAR-INFRARED TEMPLATE DERIVED FROM I Zw 1 FOR THE Fe II EMISSION IN ACTIVE GALAXIES

A. Garcia-Rissmann, A. Rodríguez-Ardila, T. A. A. Sigut, A. K. Pradhan
2012 Astrophysical Journal  
In AGN spectra, a series of FeII multiplets form a pseudo-continuum that extends from the ultraviolet to the near-infrared (NIR). This emission is believed to originate in the Broad Line Region (BLR), and it has been known for a long time that pure photoionization fails to reproduce it in the most extreme cases, as does the collisional-excitation alone. The most recent models by Sigut & Pradhan (2003) include details of the FeII ion microphysics and cover a wide range in ionization parameter
more » ... zation parameter log U_ion= (-3.0 -> -1.3) and density log n_H = (9.6 -> 12.6). With the aid of such models and a spectral synthesis approach, we study for the first time in detail the NIR emission of I Zw 1. The main goals are to confirm the role played by Ly\alpha-fluorescence mechanisms in the production of the FeII spectrum and to construct the first semi-empirical NIR FeII template that best represents this emission and can be used to subtract it in other sources. A good overall match between the observed FeII+MgII features with those predicted by the best fitted model is obtained, corroborating the Ly\alpha-fluorescence as a key process to understand the FeII spectrum. The best model is then adjusted by applying a deconvolution method on the observed FeII+MgII spectrum. The derived semi-empirical template is then fitted to the spectrum of Ark 564, suitably reproducing its observed FeII+MgII emission. Our approach extends the current set of available FeII templates into the NIR region.
doi:10.1088/0004-637x/751/1/7 fatcat:7n4m66tsarakhp77j76ofr4bwy