Bibcode
García-Rojas, J.; Peña, M.; Morisset, C.; Mesa-Delgado, A.; Ruiz, M. T.
Bibliographical reference
Astronomy and Astrophysics, Volume 538, id.A54
Advertised on:
2
2012
Journal
Citations
57
Refereed citations
49
Description
Context. Planetary nebulae (PNe) around Wolf-Rayet [WR] central stars
([WR]PNe) constitute a particular photoionized nebula class that
represents about 10% of the PNe with classified central stars.
Aims: We analyse deep high-resolution spectrophotometric data of 12 [WR]
PNe. This sample of [WR]PNe represents the most extensive analysed so
far, at such high spectral resolution. We aim to select the optimal
physical conditions in the nebulae to be used in ionic abundance
calculations that will be presented in a forthcoming paper.
Methods: We acquired spectra at Las Campanas Observatory with the 6.5-m
telescope and the Magellan Inamori Kyocera (MIKE) spectrograph, covering
a wavelength range from 3350 Å to 9400 Å. The spectra were
exposed deep enough to detect, with signal-to-noise ratio higher than
three, the weak optical recombination lines (ORLs) of O ii, C ii, and
other species. We detect and identify about 2980 emission lines, which,
to date, is the most complete set of spectrophotometric data published
for this type of objects. From our deep data, numerous diagnostic line
ratios for Te and ne are determined from
collisionally excited lines (CELs), ORLs, and continuum measurements (H
i Paschen continuum in particular). Results: Densities are
closely described by the average of all determined values for objects
with ne < 104 cm-3, and by
ne([Cl iii]) for the densest objects. For some objects,
ne([Ar iv]) is adopted as the characteristic density of the
high ionization zone. For Te, we adopt a three-zone
ionization scheme, where the low ionization zone is characterised by
Te([N ii]), the medium ionization zone by Te([O
iii]), and the highest ionization one by Te([Ar iv]) when
available. We compute Te from the H i Paschen discontinuity
and from He i lines. For each object, Te(H i) is, in general,
consistent with Te derived from CELs, although it has a very
large error. Values of Te(He i) are systematically lower than
the Te derived from CELs. When comparing Te(H i)
and Te(He i) it is unclear whether the behaviour of both
temperatures agrees with the predictions of the temperature fluctuations
paradigm, owing to the large errors in Te(H i). We do not
find any evidence of low-temperature, high-density clumps in our [WR]PNe
from the analysis of faint O ii and N ii plasma diagnostics, although
uncertainties dominate the observed line ratios in most objects. The
behaviour of Te([O iii])/Te([N ii]), which is
smaller for high ionization degrees, can be reproduced by a set of
combined matter-bounded and radiation-bounded models, although, for the
smallest temperature ratios, a too high metallicity seem to be required.
Based on data obtained at Las Campanas Observatory, Carnegie
Institution.Full Table 3 and Fig. 3 are available in electronic form at
http://www.aanda.org
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