000004754 001__ 4754
000004754 005__ 20200203153647.0
000004754 037__ $$aSCART-2020-0054
000004754 100__ $$aGuzman Fulgencio, Francisco
000004754 245__ $$aThe impact of inaccurate collisional excitation rates on radio recombination line observations
000004754 260__ $$c2019
000004754 520__ $$aRadio recombination lines (RRL) are an important tool in astronomy. They are used to determine the temperature, density and metallicity, and probe the structure of H II regions, active galactic nuclei (AGN), photo-dissociation regions (PDR) and molecular clouds. It is important that the underlying atomic physics theory is accurate in order to correctly interpret the observations. Currently, there are four datasets of collisional excitation rate coefficients based in several levels of theoretical approximation and semi-empirical formulas. However, these available datasets disagree by several order of magnitude at all temperatures. Collisional excitation brings the high Rydberg levels to local thermodynamic equilibrium (LTE), and is the driving mechanism for the distribution of the population in highly excited levels. We will show that these different atomic datasets produce critical disagreements in the predictions of RRL and optical depths in our models for the broad line regions (BLR) of NGC 5548, and the Orion blister nebula. We will also present a method to observationally discriminate between different collisional theories. Finally, we will show that the number of levels chosen to represent the atom is critical for the correct prediction of RRLs.
000004754 594__ $$aNO
000004754 700__ $$aChatzikos, Marios
000004754 700__ $$aBalser, Dana
000004754 700__ $$avan Hoof, Peter A. M.
000004754 700__ $$aDehghanian, Maryam
000004754 700__ $$aUlrich, Otho
000004754 700__ $$aFerland, Gary
000004754 773__ $$c412.08$$pAmerican Astronomical Society Meeting Abstracts$$v233$$y2019
000004754 8560_ $$fpeter.vanhoof@observatoire.be
000004754 905__ $$apublished in
000004754 980__ $$aNONREF