scholarly journals ON THE [ArIV]/[ArIII] LINE RATIO IN PLANETARY NEBULAE

2000 ◽  
Vol 3 (01-02) ◽  
pp. 48-50
Author(s):  
R. E. Carlos Reyes ◽  
F. Elizalde ◽  
J. E. Steiner
Keyword(s):  
Planetary Nebulae ◽  
Line Ratio

Estudios espectroscópicos anteriores de las nebulosas planetarias han demostrado que la razón de línea [ArIV] / [ArIII] observada no es reproducida por los modelos de fotoionización. Mostrados que esta discrepancia desaparece si consideramos una combinación adecuada del fator de llenarlo y de perfil de la densidad radial.

scholarly journals Bi-abundance photoionization models of planetary nebulae: determining the amount of oxygen in the metal-rich component

2020 ◽  
Vol 497 (3) ◽  
pp. 3363-3380 ◽  
Author(s):  
V Gómez-Llanos ◽  
C Morisset
Keyword(s):  
Heavy Element ◽  
Volume Fraction ◽  
Planetary Nebulae ◽  
Line Ratio ◽  
Small Contribution ◽  
Rich Region ◽  
Normal Region ◽  
Cold Metal ◽  
High Metallicity

ABSTRACT We study the hypothesis of high-metallicity clumps being responsible for the abundance discrepancy found in planetary nebulae between the values obtained from recombination and collisionally excited lines. We generate grids of photoionization models combining cold metal-rich clumps emitting the heavy element recombination lines, embedded in a normal metallicity region responsible for the forbidden lines. The two running parameters of the grid are the metallicity of the clumps and its volume fraction relative to the whole nebula. We determine the density and temperatures (from the Balmer jump and the [O iii] 5007/4363 Å line ratio) and the ionic abundances from the collisional and recombination lines, as an observer would do. The metallicity of the near-to-solar region is recovered, while the metallicity of the clumps is systematically underestimated by up to two orders of magnitude. This is mainly because most of the Hβ emission is coming from the ‘normal’ region, and only the small contribution emitted by the metal-rich clumps should be used. We find that a given ADF(O++) can be reproduced by a small amount of rich clumps, or a bigger amount of less rich clumps. Finally, comparing with the observations of NGC 6153, we find two models that reproduce its ADF(O++) and the observed electron temperatures. We determine the fraction of oxygen embedded in the metal-rich region (with a fraction of volume less than 1 per cent) to be roughly between 25 per cent and 60 per cent of the total amount of oxygen in the nebula (a few 10−3M⊙).

scholarly journals The UV and optical reddening law to the Galactic Bulge and CNO abundances in Bulge planetary nebulae

1993 ◽  
Vol 153 ◽  
pp. 337-338
Author(s):  
N.A. Walton ◽  
M.J. Barlow ◽  
R.E.S. Clegg
Keyword(s):  
Galactic Disk ◽  
Planetary Nebulae ◽  
Line Ratio ◽  
Solar Neighbourhood ◽  
Balmer Line ◽  
Galactic Bulge ◽  
The Mean ◽  
Cno Abundances ◽  
Halo Population ◽  
Selective Extinction

An analysis of the differential ultraviolet extinction towards four bulge planetary nebulae, based on the observed line ratio of He II 1640/4686Å, shows that the ultraviolet reddening law towards the bulge is much steeper than in the solar neighbourhood. An analysis of the optical reddening law for 42 bulge PN, based upon observed Balmer line ratios and Hβ to radio free-free flux ratios, is presented. The optical reddening law towards the bulge is steeper than in the local ISM, and thus the ratio of total to selective extinction, Rv = 2.29 (± 0.50), is lower than the standard solar neighbourhood value of Rv = 3.10.We present abundance determinations, in particular C/H and C/O ratios, for 11 Galactic bulge PN, based on spectrophotometry in the UV from IUE and in the optical from the Anglo-Australian Telescope. The derived abundances are compared with values for PN in the Galactic disk. The mean C/O ratio for bulge PN is significantly lower than that found for Galactic disk PNs. Additionally we present an abundance analysis of the very metal-poor halo population PN M2-29, which is located in the bulge.

scholarly journals The Spatio-Kinematic Structure of the CO Envelopes in Evolved Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 224-224
Author(s):  
R. Bachiller ◽  
P.J. Huggins ◽  
P. Cox ◽  
T. Forveille
Keyword(s):  
Angular Resolution ◽  
Planetary Nebulae ◽  
Line Ratio ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Excitation Temperature ◽  
Kinematic Structure ◽  
Ellipsoidal Shell ◽  
Polar Caps ◽  
Resolution Mapping

We report high angular resolution mapping of the CO (J=2→1 and 1→0) lines in three evolved planetary nebulae (PNe): NGC 6781, NGC 6772, and VV47. The CO 2→1 observations of the ring-like nebula NGC 6781 provide the most detailed map to date of the kinematic structure of a PN envelope. The data are well explained with a model consisting of a thin, clumpy, ellipsoidal shell, which is open at the ends and is expanding with a velocity proportional to distance from the star. The molecular shell of NGC 6772 appears similar, but the gas is more confined to an equatorial ring and is much more incomplete. The molecular gas in VV 47 is in two clumpy lobes, which are likely to be the only surviving molecular condensations from an earlier, more extended equatorial distribution of the same kind. The average CO excitation temperature of these PNe is found to be >23 K from the CO 2→1/1→0 line ratio, and the mass of molecular gas is estimated to be 0.1, 0.02, and 0.002 M⊙ in NGC 6781, NGC 6772, and VV 47, respectively. It appears that the ring-like PNe are formed from the dissociation and ionization of neutral ellipsoidal shells; destruction of the envelope begins with the rapid ionization of the least dense polar caps, and continues until the densest molecular material at the nebular waist is fully ionized.

scholarly journals The effect of the slit configuration on the H2 1-0 s(1) to Br γ line ratio of spatially resolved planetary nebulae

2020 ◽  
Vol 497 (3) ◽  
pp. 3180-3190
Author(s):  
Isabel Aleman
Keyword(s):  
Numerical Simulations ◽  
Planetary Nebulae ◽  
Line Ratio ◽  
Excitation Mechanism ◽  
Limited Region ◽  
Spectroscopic Observations ◽  
Spatially Resolved ◽  
Peak Emission

ABSTRACT The H2 1-0 S(1)/Br γ ratio (R(Br γ)) is used in many studies of the molecular content in planetary nebulae (PNe). As these lines are produced in different regions, the slit configuration used in spectroscopic observations may have an important effect on their ratio. In this work, observations and numerical simulations are used to demonstrate and quantify such effect in PNe. The study aims to assist the interpretation of observations and their comparison to models. The analysis shows that observed R(Br γ) ratios reach only values up to 0.3 when the slit encompasses the entire nebula. Values higher than that are only obtained when the slit covers a limited region around the H2 peak emission and the Br γ emission is then minimized. The numerical simulations presented show that, when the effect of the slit configuration is taken into account, photoionization models can reproduce the whole range of observed R(Br γ) in PNe, as well as the behaviour described above. The argument that shocks are needed to explain the higher values of R(Br γ) is thus not valid. Therefore, this ratio is not a good indicator of the H2 excitation mechanism as suggested in the literature.

scholarly journals The Spatial Distribution of Line Ratio O III/O II in High Excitation Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 228-228
Author(s):  
A. Noriega-Crespo ◽  
M. McCall
Keyword(s):  
Spatial Distribution ◽  
Density Distribution ◽  
Charge Exchange ◽  
Planetary Nebulae ◽  
Line Ratio ◽  
High Excitation ◽  
Exchange Coefficient ◽  
Gas Density ◽  
Image Position

Previous attempts to model the integrated line ratio [O III] 5007 A/[O II] 3727 A for high excitation planetary nebulae (Che and Köppen 1983) have suggested that the charge exchange coefficient (k) for the reaction could be 10 times smaller than the predicted theoretical value. The influence of other factors that may contribute to differences in the O III/O II ratio, such as the ionizing spectrum and the nebular gas density distribution, seem to be relatively small in the high excitation nebulae.

The O III 52 ▪m/88 ▪m emission-line ratio in planetary nebulae

1988 ◽  
Vol 9 (4) ◽  
pp. 237-241 ◽  
Author(s):  
F. P. Keenan ◽  
K. M. Aggarwal
Keyword(s):  
Emission Line ◽  
Planetary Nebulae ◽  
Line Ratio

Planetary Nebulae Dust as Seen by Herschel

2015 ◽  
Vol 71-72 ◽  
pp. 299-300
Author(s):  
D. Ladjal ◽  
HerPlaNS Consortium
Keyword(s):  
Planetary Nebulae

A Radial Velocity and Light Curve Study of Pulsations and Binarity in Proto-Planetary Nebulae

2015 ◽  
Vol 71-72 ◽  
pp. 127-128
Author(s):  
B.J. Hrivnak ◽  
W. Lu ◽  
G. Van de Steene ◽  
H. Van Winckel ◽  
J. Sperauskas ◽  
...  
Keyword(s):  
Light Curve ◽  
Radial Velocity ◽  
Planetary Nebulae
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