First Evidence of Enhanced Recombination in Astrophysical Environments and the Implications for Plasma Diagnostics

Nemer, A.; Sterling, N. C.; Raymond, J.; Dupree, A. K.; García-Rojas, J.; Wang, Qianxia; Pindzola, M. S.; Ballance, C. P.; Loch, S. D.
Referencia bibliográfica

The Astrophysical Journal

Fecha de publicación:
Número de autores
Número de autores del IAC
Número de citas
Número de citas referidas
We report the first unambiguous observational evidence of Rydberg Enhanced Recombination (RER), a potentially important recombination mechanism that has hitherto been unexplored in low-temperature photoionized plasmas. RER shares similarities with dielectronic recombination, with the difference that the electron is captured into a highly excited state below the ionization threshold—rather than above the threshold—of the recombining ion. We predict transitions of carbon and oxygen ions that are formed via the RER process, and their relative strengths with collisional-radiative spectral models. Optical C II RER features are detected in published high-resolution spectra of eight planetary nebulae, and a C III transition has been found in the ultraviolet spectrum in a symbiotic star system. The relative intensities of these lines are consistent with their production by this recombination mechanism. Because RER has not previously been accounted for in photoionized plasmas, its inclusion in models can significantly impact the predicted ionization balance and hence abundance calculations of important astrophysical species. Calculations for {C}+ suggest that the enhancement in the total recombination rate can amount to a factor of 2.2 at 8100 K, increasing to 7.5 at T = 3500 K. These results demonstrate the importance of including RER in models of photoionized astrophysical plasmas and in elemental abundance determinations.
Proyectos relacionados
Izquierda - Imagen RGB de la nebulosa de Orión y M43 obtenida filtros estrechos con la cámara WFC en el INT: H alfa (rojo), [S II] 6716+30 (verde), [O III] 5007 (azul). Derecha - Imagen en falso color de la nebulosa planetaria NGC 6778. En azul se ve la emisión en la línea de O II tomada con el filtro sintonizable azul del instrumento OSIRIS en el GTC; en verde imagen con el filtro estrecho de [O III] del Nordic Optical Telescope (NOT).
Física de Nebulosas Ionizadas
Este proyecto mantiene dos líneas principales de investigación activas: 1) Estudio de la estructura, condiciones físicas y composición química de las nebulosas ionizadas, tanto galácticas como extragalácticas, a través del análisis detallado y modelización de sus espectros. Investigación de los gradientes de composición química a lo largo del disco
García Rojas