Poster abstract details

Recently, we derived in a homogeneous way the oxygen abundances for five H II regions and eight PNe of the solar neighborhood (at distances lower than 2 kpc), with observed spectra of high quality. We used collisionally excited lines and recombination lines, finding that in both cases the abundances derived for the PNe are 0.2 dex above those calculated for the H II regions. We compared the resulting abundances with those found for the Sun, B stars, and the diffuse ISM. A good agreement can be reached for the results implied by collisionally excited lines if the H II regions have about a quarter of their oxygen atoms deposited onto an organic refractory dust component. This dust component was previously proposed to explain the pattern of oxygen depletion in the diffuse and dense ISM. Oxygen is the element for which the derived abundances are more reliable, but results for the other elements could provide further evidence on this issue. However, this requires studying the bias introduced by ionization correction factors, which is likely to be different in H II regions and PNe. Here we present preliminary results of this analysis.