Dielectronic Recombination In Active Galactic Nuclei*

Recent X-ray satelitte observations of active galactic nuclei point out shortcomings in our understanding of low temperature dielectronic recombination (DR) for iron M- shell ions. In order to resolve this issue and to provide reliable iron M-shell DR data for modeling astrophysical plasmas, we are carrying out a series of laboratory measurements using the heavy-ion Test Storage Ring at the Max- Plank-Institute for Nuclear Physics in Heidelberg, Germany. Storage rings are currently the only laboratory method capable of studying low temperature DR. We use our results to produce experimentally- derived DR rate coefficients. We are also providing our data to atomic theorist to benchmark their DR calculations. Here we will report our recent DR results for selected Fe M-shell ions. At temperatures where these ions are predicted to form in photoionized gas, we find a significant discrepancy between our experimental results and previously recommended DR rate coefficients.