Resumen

BOHIGAS, J.. On the abundance enigma in lonized Regions. Rev. mex. astron. astrofis [online]. 2009, vol.45, n.1, pp.107-123. ISSN 0185-1101.

In ionized regions with temperature gradients and fluctuations, the ratio of the ion abundance obtained from a recombination line to that found from a collisionally excited line (CEL), or ADF, is smaller than observed (ADF > 2). Larger ADFs are found when there is an additional component that is > 30% colder. The temperature in the cold component must be ≈ 500, 200 and 100 K if the ADF found from an IR CEL is 2, 5 and 10. Most of the mass is in the hot region. The total H⁺ mass has been underestimated if it was found from the intensity of a Balmer line. [O IIII]5007/Hβ images can also render the relative distribution of cold and hot matter. The determination of accurate abundances is forestalled by the fact that observations cannot discriminate light from these components, the existence of distinct abundance sets and insufficient spectral information for the hot region.

Palabras llave : ISM: abundances; ISM: H II regions; ISM: planetary nebulae; general.