Bibcode
García-Rojas, J.; Peña, M.; Peimbert, A.
Bibliographical reference
Astronomy and Astrophysics, Volume 496, Issue 1, 2009, pp.139-152
Advertised on:
3
2009
Journal
Citations
51
Refereed citations
42
Description
Aims: We present spatially resolved high-resolution spectrophotometric
data for the planetary nebulae PB 8, NGC 2867, and PB 6. We have
analyzed two knots in NGC 2867 and PB 6 and one in PB 8. The three
nebulae are ionized by [WC] type nuclei: early [WO] for PB 6 and NGC
2867 and [WC 5-6] in the case of PB 8. Our aim is to study the behavior
of the abundance discrepancy problem (ADF) in this type of planetary
nebula. Methods: We measured a large number of optical
recombination (ORL) and collisionally excited lines (CEL), from
different ionization stages (many more than in any previous work), thus,
we were able to derive physical conditions from many different
diagnostic procedures. We determined ionic abundances from the available
collisionally excited and recombination lines. Based on both sets of
ionic abundances, we derived total chemical abundances in the nebulae
using suitable ionization correction factors. Results: From CELs,
we have found abundances typical of Galactic disk planetary nebulae.
Moderate ADF(O++) were found for PB 8 (2.57) and NGC 2867
(1.63). For NGC 2867, abundances from ORLs are higher but still
consistent with Galactic disk planetary nebulae. On the contrary, PB 8
presents a very high O/H ratio from ORLs. A high C/O was obtained from
ORLs for NGC 2867; this ratio is similar to C/O obtained from CELs and
with the chemical composition of the wind of the central star,
indicating that there was no further C-enrichment in the star, relative
to O, after the nebular material ejection. On the contrary, we found
C/O<1 in PB 8. Interestingly, we obtain (C/O)ORLs/(C/O)CELs < 1 in
PB 8 and NGC 2867; this added to the similarity between the heliocentric
velocities measured in [O iii] and O ii lines for our three objects
argue against the presence of H-deficient metal-rich knots coming from a
late thermal pulse event.
Based on data obtained at Las Campanas Observatory, Carnegie
Institution.
Table 3 is only available in electronic form at http://www.aanda.org