Bibcode
García-Rojas, J.; Esteban, C.; Mesa-Delgado, A.; Toribio San Cipriano, L.
Bibliographical reference
Astronomische Nachrichten, Vol.335, Issue 1, p.73
Advertised on:
1
2014
Citations
6
Refereed citations
5
Description
High spectral resolution spectroscopy has proved to be very useful for
the advancement of chemical abundances studies in photoionized nebulae,
such as H II regions and planetary nebulae (PNe). Classical analyses
make use of the intensity of bright collisionally excited lines (CELs),
which have a strong dependence on the electron temperature and density.
By using high resolution spectrophotometric data, our group has led the
determination of chemical abundances of some heavy element ions, mainly
O++, O+, and C++ from faint
recombination lines (RLs), allowing us to deblend them from other nearby
emission lines or sky features. The importance of these lines is that
their emissivity depends weakly on the temperature and density structure
of the gas. The unresolved issue in this field is that recombination
lines of heavy element ions give abundances that are about 2-3 times
higher than those derived from CELs - in H II regions - for the same
ion, and can even be a factor of 70 times higher in some PNe. This
uncertainty puts into doubt the validity of face values of metallicity
that we use as representative not only for ionized nebulae in the Local
Universe, but also for star-forming dwarf and spiral galaxies at
different redshifts. Additionally, high-resolution data can allow us to
detect and deblend faint lines of neutron capture element ions in PNe.
This information would introduce further restrictions to evolution
models of AGBs and would help to quantify the chemical enrichment in
s-elements produced by low and intermediate mass stars. The availability
of an échelle spectrograph at the E-ELT will be of paramount
interest to: (a) extend the studies of heavy-element recombination lines
to low metallicity objects, (b) to extend abundance determinations of
s-elements to planetary nebulae in the extragalactic domain and to
bright Galactic and extragalactic H II regions.
Related projects
Physics of Ionized Nebulae
The research that is being carried out by the group can be condensed into two main lines: 1) Study of the structure, dynamics, physical conditions and chemical evolution of Galactic and extragalactic ionized nebulae through detailed analysis and modelization of their spectra. Investigation of chemical composition gradients along the disk of our
Jorge
García Rojas