scholarly journals The Distance Scale of Planetary Nebulae

1978 ◽  
Vol 76 ◽  
pp. 35-46
Author(s):  
Wm. Liller
Keyword(s):  
Planetary Nebulae ◽  
Distance Scale ◽  
Stellar Systems ◽  
Lyman Continuum ◽  
Improved Model ◽  
Distance Indicators

The spectacular success of the so-called Shklovsky method of finding distances to planetary nebulae which are optically thin to the Lyman continuum (Shklovsky 1956; see also Minkowski and Aller 1954) has produced within us a rather breath-taking boldness. Following the careful application of this method to more than 600 planetaries by Cahn and Kaler (1971), we now have the audacity to use planetaries as reliable distance indicators to derive an improved model of our own galaxy (Cahn 1976), trace the evolution of stars in their post-giant stages (O'Dell 1974, Cahn and Wyatt 1976), and even determine distances to other stellar systems (Ford, Jenner, and Epps 1973). At the Tatranská Lomnica meeting 10 years ago, there seemed little hope that one day soon planetary nebulae distances would become reliable. That day is near if not here already.

scholarly journals Distance Indicators in the Magellanic Clouds

1983 ◽  
Vol 6 ◽  
pp. 209-216 ◽  
Author(s):  
J.A. Graham
Keyword(s):  
Chemical Evolution ◽  
Comparative Studies ◽  
Hubble Constant ◽  
Magellanic Clouds ◽  
Distance Scale ◽  
Stellar Systems ◽  
Age Range ◽  
Distance Indicators ◽  
The Universe

In talking about the overall distance scale of the Universe and the Hubble Constant, the Magellanic Clouds are good places to start. They are stellar systems large enough to contain stars, clusters and nebulae of all types, covering a wide age range. With modern telescopes and detectors, we are able to observe stars from the very bright down to those fainter intrinsically than our own Sun. From comparative studies, we may thus establish our basic calibrations of bright objects before moving out to measure the Universe at large. At the same time, the fact that both Magellanic Clouds are independently evolving galaxies, enables us to separate the effects of stellar age and chemical evolution on the calibrations that we make.

Planetary Nebulae as Extragalactic Distance Indicators

2003 ◽  
Vol 209 ◽  
pp. 617-624 ◽  
Author(s):  
Robin Ciardullo
Keyword(s):  
Excellent Agreement ◽  
Planetary Nebula ◽  
Surface Brightness ◽  
Luminosity Function ◽  
Planetary Nebulae ◽  
General Purpose ◽  
Distance Scale ◽  
Standard Candle ◽  
Surface Brightness Fluctuations ◽  
Distance Indicators

The planetary nebula luminosity function (PNLF) plays a key role in the distance ladder, as it is the only general purpose standard candle that is applicable to both Pop I and Pop II systems. We review the physics underlying the method, and compare its distances to distances obtained from Cepheids and surface brightness fluctuations (SBF). We show that PNLF distances agree with the geometric distances to the LMC and NGC 4258, and that, on a galaxy-by-galaxy basis, the relative PNLF, Cepheid, and SBF distances are in excellent agreement with no systematic trends. However, even though the PNLF and SBF methods are both calibrated by Cepheids, the PNLF distance scale is ~17% smaller than the SBF scale. We discuss this offset, and examine the possible causes of the discrepancy.

scholarly journals The Dust Content of Planetary Nebulae with Neutral Halos

1989 ◽  
Vol 131 ◽  
pp. 202-202
Author(s):  
M. G. Hoare
Keyword(s):  
Significant Contribution ◽  
Large Fraction ◽  
Planetary Nebulae ◽  
Far Infrared ◽  
Dust Content ◽  
Lyman Continuum ◽  
Apparent Decrease ◽  
Gas Ratio

Young planetary nebulae (PN) which are still optically thick in the Lyman continuum can have a large fraction of material in neutral halos surrounding the ionized zone. The cool dust in the neutral region can make a significant contribution to the far infrared flux, reducing the derived dust-to-gas ratio. This is important when attempting to understand the apparent decrease in dust-to-gas ratio with nebular radius (age) suggested by Pottasch et al. (1984).

scholarly journals The Ionization of Planetary Nebulae

1968 ◽  
Vol 34 ◽  
pp. 190-204 ◽  
Author(s):  
Robert E. Williams
Keyword(s):  
Ionizing Radiation ◽  
Emission Line ◽  
Radiation Field ◽  
Planetary Nebulae ◽  
Model Atmosphere ◽  
Evolutionary Sequence ◽  
Lyman Continuum ◽  
The Mean ◽  
Central Stars

The ionization of the most abundant elements in planetary nebulae has been determined for a number of models of nebulae at different epochs in their expansion. The values used for the temperatures and radii of the central stars and the sizes and densities of the shells have come from Seaton's evolutionary sequence. The ionizing radiation field has been taken from model atmosphere calculations of the central stars by Gebbie and Seaton, and Böhm and Deinzer. Emission-line fluxes have been calculated for the models and compared with observations of planetary nebulae by O'Dell, Osterbrock's group, and Aller and his collaborators. Results indicate that the central stars have strong He+ Lyman continuum excesses, similar to those predicted by Gebbie and Seaton. The mean abundance determinations for the nebulae made by Aller are confirmed, with the exception of nitrogen, which appears to be 3 or 4 times more abundant than his value. It is also seen that the electron temperatures of the nebulae are higher than previous theoretical determinations, providing better agreement with empirically derived values.

scholarly journals The Absorption of Hell Lyα Photons in Planetary Nebulae

1978 ◽  
Vol 76 ◽  
pp. 166-166
Author(s):  
D.R. Flower ◽  
M. Perinotto
Keyword(s):  
Thermal Structure ◽  
Large Fraction ◽  
Central Zone ◽  
Planetary Nebulae ◽  
High Excitation ◽  
Lyman Continuum ◽  
Line Transfer ◽  
Astronomy And Astrophysics

The fate of the Hell Lya photons, produced during recombinations of the He++ ions and electrons, is important in considerations of the ionization and thermal structure of high excitation nebulae (Flower, 1968, IAU Symp. No. 34, Planetary Nebulae, p. 77). Hummer and Seaton (1964, M.N.R.A.S. 127, 217) effectively supposed that these photons are absorbed by H° in the central (He++) zone, whereas detailed line transfer calculations (Weymann and Williams, 1969, Ap. J. 157, 1201; Harrington, 1972, Ap. J. 176, 127) suggest that a large fraction of the photons escapes from the central zone. We consider the effects of the absorption of these photons on the ionization and thermal structure of the outer (He+, H+) zone of a nebula which is optically thick in the HI Lyman continuum. (Paper will appear in Astronomy and Astrophysics.)

scholarly journals Nonlinear Convective Pulsation Models of Second Overtone SMC Cepheids

2002 ◽  
Vol 185 ◽  
pp. 420-423
Author(s):  
M. Marconi ◽  
G. Bono ◽  
F. Caputo
Keyword(s):  
Short Distance ◽  
Selection Criteria ◽  
Distance Scale ◽  
Model Predictions ◽  
Distance Indicators

AbstractNonlinear convective pulsation models representative of SMC Cepheids pulsating in the second overtone mode are presented. Model predictions are compared with observations and implications are derived for second overtone selection criteria. The role of overtone Cepheids as distance indicators is finally investigated and the derived distance scale is at odds with the so called short distance scale.

scholarly journals The origin of the most luminous Planetary Nebulae

2016 ◽  
Vol 12 (S323) ◽  
pp. 386-387
Author(s):  
Rebeca Galera-Rosillo ◽  
Romano L. M. Corradi ◽  
Bruce Balick ◽  
Karen Kwitter ◽  
Antonio Mampaso ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Planetary Nebulae ◽  
Stellar Systems ◽  
Systematic Effort ◽  
The Masses

AbstractAs part of a systematic effort to characterize the properties and progenitors of the most luminous planetary nebulae (PNe), we obtained a sample among the brightest PNe in two stellar systems of different metallicities: LMC (Z/Z⊙~0.5) and M31 (Z/Z⊙~1) by means of a combined effort with the VLT and the 10mGTC. Modelling of these data will allow us to infer the masses of the stellar progenitors, gaining insights into the controversial origin of the universal cutoff of the Planetary Nebulae Luminosity Function (PNLF).

scholarly journals Expansion distances of Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 29-39 ◽  
Author(s):  
Yervant Terzian
Keyword(s):  
Planetary Nebulae ◽  
Distance Scale ◽  
Radial Expansion ◽  
Radio Data

The distances of planetary nebulae are discussed as derived from their angular expansions and radial expansion velocities. An assessment is given of distances derived by this method both at optical and radio wavelengths. The recent VLA radio data show promise in establishing a more accurate distance scale for planetary nebulae.

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