1 research outputs found
When Shape Matters: correcting the ICFs to derive the chemical abundances of bipolar and elliptical PNe
The extraction of chemical abundances of ionised nebulae from a limited
spectral range is usually hampered by the lack of emission lines corresponding
to certain ionic stages. So far, the missing emission lines have been accounted
for by the ionisation correction factors (ICFs), constructed under simplistic
assumptions like spherical geometry by using 1-D photoionisation modelling.
In this contribution we discuss the results (Goncalves et al. 2011, in prep.)
of our ongoing project to find a new set of ICFs to determine total abundances
of N, O, Ne, Ar, and S, with optical spectra, in the case of non-spherical PNe.
These results are based on a grid of 3-D photoionisation modelling of round,
elliptical and bipolar shaped PNe, spanning the typical PN luminosities,
effective temperatures and densities.
We show that the additional corrections --to the widely used Kingsburgh and
Barlow (1994) ICFs-- are always higher for bipolars than for ellipticals.
Moreover, these additional corrections are, for bipolars, up to: 17% for
oxygen, 33% for nitrogen, 40% for neon, 28% for argon and 50% for sulphur.
Finally, on top of the fact that corrections change greatly with shape, they
vary also greatly with the central star temperature, while the luminosity is a
less important parameter.Comment: Oral contribution (4 pages, 2 figures) to IAU Symposium 283:
"Planetary Nebulae: An Eye to the Future" held in Puerto de la Cruz,
Tenerife, Spain in July 25th-29th 201