scholarly journals IFU Spectroscopy of Southern Planetary Nebulae V: Low-Ionisation Structures

2017 ◽  
Vol 34 ◽  
Author(s):  
A. Ali ◽  
M. A. Dopita
Keyword(s):  
Emission Line ◽  
Planetary Nebulae ◽  
Central Star ◽  
Chemical Compositions ◽  
Physical Analysis ◽  
Type I ◽  
High Excitation ◽  
Chemical Abundances ◽  
Physical Conditions ◽  
Integral Field Spectroscopy

AbstractIn this fifth paper of the series, we examine the spectroscopy and morphology of four southern Galactic planetary nebulae Hen 2-141, NGC 5307, IC 2553, and PB 6 using new integral field spectroscopy data. The morphologies and ionisation structures of the sample are given as a set of emission-line maps. In addition, the physical conditions, chemical compositions, and kinematical characteristics of these objects are derived. The results show that PB 6 and Hen 2-141 are of very high excitation classes and IC 2553 and NGC 5307 are mid to high excitation objects. The elemental abundances reveal that PB 6 is of Type I, Hen 2-141 and IC 2553 are of Type IIa, and NGC 5307 is of Type IIb/III. The observations unveil the presence of well-defined low-ionisation structures or ‘knots’ in all objects. The diagnostic diagrams reveal that the excitation mechanism of these knots is probably by photoionisation of dense material by the nebular central stars. The physical analysis of six of these knots show no significant differences with their surrounding nebular gas, except their lower electron densities. In spite of the enhancement of the low-ionisation emission lines of these knots, their chemical abundances are nearly comparable to their surrounding nebulae, with the exception of perhaps slightly higher nitrogen abundances in the NGC 5307 knots. The integrated spectrum of IC 2553 reveals that nearly all key lines that have led researchers to characterise its central star as a weak-emission line star type are in fact of nebular origin.

scholarly journals Twenty years of observations of PM 1-188: Its chemical abundances and extraordinary kinematics

2021 ◽  
Author(s):  
Miriam Peña ◽  
Liliana Hernández-Martínez ◽  
Francisco Ruiz-Escobedo
Keyword(s):  
Chemical Composition ◽  
Planetary Nebula ◽  
Central Star ◽  
Emission Lines ◽  
Type I ◽  
Chemical Abundances ◽  
Line Intensities ◽  
Physical Conditions ◽  
The Past ◽  
Spectrophotometric Data

Abstract The analysis of 20 years of spectrophotometric data of the double shell planetary nebula PM 1-188 is presented, aiming to determine the time evolution of the emission lines and the physical conditions of the nebula, as a consequence of the systematic fading of its [WC 10] central star whose brightness has declined by about 10 mag in the past 40 years. Our main results include that the [O iii], [O ii], [N ii] line intensities are increasing with time in the inner nebula as a consequence of an increase in electron temperature from 11 000 K in 2005 to more than 14 000 K in 2018, due to shocks. The intensity of the same lines are decreasing in the outer nebula, due to a decrease in temperature, from 13 000 K to 7000 K, in the same period. The chemical composition of the inner and outer shells was derived and they are similar. Both nebulae present subsolar O, S and Ar abundances, while they are He, N and Ne rich. For the outer nebula the values are 12+log He/H = 11.13 ± 0.05, 12+log O/H = 8.04 ± 0.04, 12+log N/H = 7.87 ± 0.06, 12+log S/H = 7.18 ± 0.10 and 12+log Ar = 5.33 ± 0.16. The O, S and Ar abundances are several times lower than the average values found in disc non-Type I PNe, and are reminiscent of some halo PNe. From high resolution spectra, an outflow in the N-S direction was found in the inner zone. Position-velocity diagrams show that the outflow expands at velocities in the −150 to 100 km s−1 range, and both shells have expansion velocities of about 40 km s−1.

scholarly journals The Magellanic Clouds and Planetary Nebulae

1984 ◽  
Vol 108 ◽  
pp. 363-374
Author(s):  
Manuel Peimbert
Keyword(s):  
Emission Line ◽  
Chemical Evolution ◽  
Stellar Evolution ◽  
Central Star ◽  
Magellanic Clouds ◽  
Chemical Compositions ◽  
Intermediate Mass ◽  
Chemical Abundances ◽  
Line Intensities ◽  
Intermediate Mass Stars

A review of the statistics, emission line intensities, central star fluxes, radial velocities and chemical compositions of PN in the MC is given. From these data a discussion is made of: a) the distance scale, b) the envelope mass, c) the comparison between the observed chemical abundances and those predicted from stellar evolution models and, d) the effect that intermediate mass stars have on the chemical evolution of the MC and our galaxy.

Spectrophotometry of Selected Planetary Nebulae of Type I in the Magellanic Clouds

1993 ◽  
Vol 155 ◽  
pp. 584-584 ◽  
Author(s):  
S. Torres-Peimbert ◽  
M. Peimbert ◽  
M.T. Ruitz ◽  
M. Peña
Keyword(s):  
Wavelength Range ◽  
Planetary Nebulae ◽  
Magellanic Clouds ◽  
Type I ◽  
Chemical Abundances ◽  
Spectroscopic Observations ◽  
Physical Conditions

We carried out spectroscopic observations of N67 (in the SMC), and N66, N97 and N102 (in the LMC) with the 4-m telescope of CTIO. The wavelength range is λλ 3500–7400. From these we obtained physical conditions and chemical abundances of these objects.

scholarly journals Planetary nebulae in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 299-306 ◽  
Author(s):  
M. A. Dopita
Keyword(s):  
Planetary Nebulae ◽  
Central Star ◽  
Magellanic Cloud ◽  
Expansion Velocity ◽  
H Ii Regions ◽  
Type I ◽  
Chemical Abundances ◽  
Processed Material ◽  
Density Radius ◽  
Central Stars

We present a simple two-wind model for the evolution of the Magellanic Cloud planetary nebulae (PN) which reproduces the observed density / radius / ionised mass relationships, and serves to define the geometrical relationship between the ionised nebula and the star. From self-consistent photoionisation modelling of 78 Magellanic Cloud PN, we have constructed the H-R Diagram for the central stars, and have derived both the chemical abundances and the nebular parameters. We find that the central stars have masses generally between 0.55 and 0.7 M⊙. Type I PN have more massive precursors, and show clear evidence for the Third dredge-up episode and for the dredge-up of ON processed material. The expansion velocity of the nebula is closely correlated with the position of the central star on the H-R Diagram, proving that the nebula undergoes continuous acceleration. Excluding Type I PN, the mean abundances derived for the LMC and the SMC agree with those derived from H II regions and evolved, radiative SNR.

scholarly journals 3D photoionization models: the bipolar PN IC 4406

1997 ◽  
Vol 180 ◽  
pp. 231-231
Author(s):  
R. Gruenwald ◽  
S. M. Viegas ◽  
D. Broguière
Keyword(s):  
Planetary Nebula ◽  
Three Dimensional ◽  
Chemical Properties ◽  
Diffuse Radiation ◽  
Central Star ◽  
Type I ◽  
Chemical Abundances ◽  
Line Intensities ◽  
Physical Conditions ◽  
Self Consistent

A three-dimensional (3D) self-consistent photoionization code is developed in order to build more realistic models for asymmetrical and/or inhomogeneous photoionized nebulae. With these models the assumption of spherical or plane-parallel symmetry can be dropped and models with various geometries can be treated. The gaseous region is divided into numberous cubic cells, and the physical conditions in each cell are obtained taking into account the effect of the other cells in the optical depth and their contribution into the diffuse radiation. A model for IC 4406, which is a typical example of bipolar planetary nebula is presented. The model assumes a torus of dense material around the central star, as suggested in the literature. Its presence is confirmed by the model, in particular by the shape of the theoretical Hα + [NII] isophotal map. The chemical abundances required to explain the observed line intensities indicate that the chemical properties of this bipolar nebula are not characteristic of type I planetaries. A detailed paper will be published in Ap.J. (FAPESP, CNPq)

scholarly journals Chemical Enrichment and Central Star Properties

1993 ◽  
Vol 155 ◽  
pp. 572-572
Author(s):  
C.Y. Zhang
Keyword(s):  
Planetary Nebulae ◽  
Central Star ◽  
Agb Stars ◽  
Physical Processes ◽  
Chemical Abundances ◽  
Core Mass ◽  
Chemical Enrichment ◽  
The Core ◽  
Stellar Temperature ◽  
Independent Parameters

We have selected a sample of planetary nebulae, for which the core masses are determined using distance-independent parameters (Zhang and Kwok 1992). The chemical abundances of He, N, O, and C are taken from the literature for them. Relationships of the ratios of He/H, N/O, and C/O with various stellar parameters of planetary nebulae (PN), such as the core mass, the mass of the core plus the ionized nebular gas, the stellar age and temperature, are examined. It is found that the N/O increases with increasing mass, while the C/O first increases and then decreases with the core mass. No strong correlation seems to exist between the He/H and the core mass. A correlation of the N/O and He/H with the stellar temperature exists. The current dredge-up theory for the progenitor AGB stars cannot satisfactorily account for these patterns of chemical enrichment in PN. Furthermore, the correlations of the N/O and He/H with the stellar age and temperature indicate that besides the dredge-ups in the RG and AGB stages, physical processes that happen in the planetary nebula stage may also play a role in forming the observed patterns of chemical enrichment in the planetary nebulae.

scholarly journals Helium and Oxygen Abundances in SMC Planetary Nebulae

2000 ◽  
Vol 198 ◽  
pp. 234-235
Author(s):  
R. D. D. Costa ◽  
J. A. de Freitas Pacheco ◽  
T. P. Idiart
Keyword(s):  
Spectroscopic Data ◽  
Planetary Nebulae ◽  
Hii Regions ◽  
Physical Parameters ◽  
Type I ◽  
Chemical Abundances ◽  
High Quality

In this work we report new high quality spectroscopic data for a sample of PNe in the SMC, aiming to derive physical parameters and chemical abundances, in particular to settle the question concerning the oxygen discrepancy found for type I planetaries with respect to stars and HII regions.

scholarly journals Models of Planetary Nebulae: Generalisation of the Multiple Winds Model

1989 ◽  
Vol 131 ◽  
pp. 411-424 ◽  
Author(s):  
F. D. Kahn
Keyword(s):  
Planetary Nebula ◽  
High Speed ◽  
Planetary Nebulae ◽  
Central Star ◽  
Theoretical Description ◽  
Basic Theory ◽  
Spectral Lines ◽  
High Excitation ◽  
General Shape ◽  
Fast Wind

According to the multiple winds model a planetary nebula forms as the result of the interaction of a fast wind from the central star with the superwind that had previously been emitted by the progenitor star. The basic theory which deals with the spherically symmetrical case is briefly summarised. Various improvements are then considered in turn. A better history is clearly needed of the way that the central star becomes hotter, it is unrealistic to make the assumption that the superwind is spherically symmetrical, and finally there are likely to be important instabilities at some of the interfaces in the PN, notably that between the shocked superwind and the HII layer. These changes in the theoretical description produce a better understanding of the conditions in the outer parts of a PN and of the nature of its general shape, and they should lead to an explanation for the occurrence of high speed motions, and of highly ionized species and high excitation spectral lines.

The role of shocks in the determination of empirical abundances for type-I PNe

2018 ◽  
Vol 14 (S343) ◽  
pp. 377-378
Author(s):  
Roberto D. D. Costa ◽  
Paulo J. A. Lago
Keyword(s):  
Planetary Nebulae ◽  
Type I ◽  
Correction Factors ◽  
Chemical Abundances

AbstractWe investigate, in the light of new diagnostic diagrams, the role of shocks in the ionization profile of type-I planetary nebulae, and their relation to the empirical derivation of chemical abundances. We apply our technique to two well-known type-I objects: NGC 2440 and NGC 6302. Our results indicate that shocks play a very important role in the spectra of both nebulae and, since the presence of shocks reinforces the flux of low ionization lines, this artificial reinforcement can lead to incorrect chemical abundances, when they are derived through Ionization Correction Factors, at least for type-I PNe.

scholarly journals The impact of spectra quality on nebular abundances

2020 ◽  
Vol 495 (1) ◽  
pp. 1016-1034 ◽  
Author(s):  
Mónica Rodríguez
Keyword(s):  
Planetary Nebulae ◽  
The Other ◽  
Statistical Equilibrium ◽  
Emission Lines ◽  
Reference Spectrum ◽  
Equilibrium Equations ◽  
Chemical Abundances ◽  
Physical Conditions ◽  
Observational Errors ◽  
The Impact

ABSTRACT I explore the effects of observational errors on nebular chemical abundances using a sample of 179 optical spectra of 42 planetary nebulae (PNe) observed by different authors. The spectra are analysed in a homogeneous way to derive physical conditions and ionic and total abundances. The effects of recombination on the [O ii] and [N ii] emission lines are estimated by including the effective recombination coefficients in the statistical equilibrium equations that are solved for O+ and N+. The results are shown to be significantly different than those derived using previous approaches. The O+ abundances derived with the blue and red lines of [O ii] differ by up to a factor of 6, indicating that the relative intensities of lines widely separated in wavelength can be highly uncertain. In fact, the He ii lines in the range 4000–6800 Å imply that most of the spectra are bluer than expected. Scores are assigned to the spectra using different criteria and the spectrum with the highest score for each PN is taken as the reference spectrum. The differences between the abundances derived with the reference spectrum and those derived with the other spectra available for each object are used to estimate the 1σ observational uncertainties in the final abundances: 0.11 dex for O/H and Ar/H, 0.14 dex for N/H, Ne/H, and Cl/H, and 0.16 dex for S/H.

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