Bibcode
DOI
Ruiz, María Teresa; Peimbert, Antonio; Peimbert, Manuel; Esteban, César
Bibliographical reference
The Astrophysical Journal, Volume 595, Issue 1, pp. 247-258.
Advertised on:
9
2003
Journal
Citations
67
Refereed citations
56
Description
Echelle spectrophotometry of the planetary nebula NGC 5307 is presented.
The data consist of Very Large Telescope Ultraviolet Visual Echelle
Spectrograph observations in the 3100-10360 Å range. Electron
temperatures and densities have been determined using different line
intensity ratios. We determine the H, He, C, and O abundances based on
recombination lines; these abundances are almost independent of the
temperature structure of the nebula. We also determine the N, O, Ne, S,
Cl, and Ar abundances based on collisionally excited lines; the ratios
of these abundances relative to that of H depend strongly on the
temperature structure of the nebula. From the O II/[O III] line
intensity ratios we find a t2=0.056+/-0.005. The chemical
composition of NGC 5307 is compared with those of the Sun and the Orion
Nebula. From the study of the relative intensities of the O II
recombination lines of multiplet 1 in this and other nebulae, it is
found that for electron densities smaller than about 5000
cm-3 collisional redistribution is not complete; this effect
has to be taken into account to derive the O abundances for those cases
in which not all the lines of the multiplet are observed. From the O II
λ4649 versus Ne(Cl III) diagram we find a critical
electron density of 1325 cm-3 for collisional redistribution
of the O II lines of multiplet 1. Based on this diagram, we also argue
that the O II and the [O III] lines originate in the same regions. We
also find that the radial velocities and the FWHM of the O II and [O
III] lines in NGC 5307 are similar, supporting the previous result.
These two results imply that for NGC 5307 and probably for many other
gaseous nebulae chemical inhomogeneities are not responsible for the
large temperature fluctuations observed.
Based on observations collected at the European Southern Observatory,
Chile, proposal ESO 68.C-0149(A).