Improved simulations of astrophysical plasmas: Computation of new dielectronic recombination data

Most hard astrophysical numbers come from the quantitative analysis and interpretation of spectra, frequently of emitting plasmas that arc at extremely low density by laboratory standards, and as a result the gas is in a profoundly non-equilibrium state. The physical conditions and the resulting spectrum cannot be predicted by analytical theory, and large-scale numerical simulations must be done instead. The results can be directly compared with a broad range of X-ray, UV, and IR observations, but rely on a vast sea of basic atomic and molecular cross sections and rates. We have initiated a program to carry out detailed theoretical calculations for dielectronic recombination (DR) of specific 2nd, 3rd, and 4th row ions. These are investigated using a radiation-damped R-matrix approach as well as the perturbative AUTOSTRUCTURE package. These independently-determined DR rates are benchmarked against each other and, where possible, against, experimental results. Computed data are disseminated to the astrophysics community via our web page, and are used by us in the lion-equilibrium plasma simulation code CLOUDY to enable more accurate simulations of ionized emission and absorption line gases.