The origin of Fe II and [Fe II] emission lines in the 4,000-10,000 Å range in the BD Weigelt Blobs of Eta Carinae

Abstract:
We present numerical simulations that reproduce the salient features of the amazingly strong [Fe ii andFe ii emission spectra in the B and D Weigelt blobs of Carinae. For our studies we have used spectraobtained during the 1998 epoch observations with the Hubble Space Telescope (HST). The spectrum of the Band D Weigelt blobs dominates in [Fe ii and Fe ii emission lines. The same observations show no Fe i orFe iii. We have compared our measurements of the strongest (200) [Fe ii and Fe ii lines and blends in thespectrum with theoretical predictions. Our predictions are based on non-LTE modeling of the Fe ii atom,which includes the lowest 371 energy levels (all levels up to 11.6 eV). We have investigated the dependence ofthe spectrum on electron density, pumping by the blackbody-like stellar continuum, and intense Lyemission. We nd that radiative pumping is essential in explaining the observed spectrum. We have identiedthe main pumping routes responsible for the observed Fe ii emission. Comparison between the model andobservations reveals details of the radiation eld. Pumping by the blackbody-like stellar radiation eld from Carinae explains the numerous strong [Fe ii and Fe ii lines in the range of 40006500 . The strongest Fe iilines in a range of 800010000 are pumped by intense Ly radiation.