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Planetary nebula distances re-examined: an improved statistical scale
The distances of planetary nebulae (PNe) are still quite uncertain.Although observational estimates are available for a small proportion ofPNe, based on statistical parallax and the like, such distances are verypoorly determined for the majority of galactic PNe. In particular,estimates of so-called `statistical' distance appear to differ byfactors of ~2.7.We point out that there is a well-defined correlation between the 5-GHzluminosity of the sources, L5, and their brightnesstemperatures, TB. This represents a different trend to thoseinvestigated in previous statistical analyses, and permits us todetermine independent distances to a further 449 outflows. Thesedistances are shown to be closely comparable to those determined using aTB-R correlation, providing that the latter trend is taken tobe non-linear.This non-linearity in the TB-R plane has not been noted inprevious analyses, and is likely responsible for the broad (andconflicting) ranges of distance that have previously been published.Finally, we point out that there is a close accord between observedtrends within the L5-TB and TB-Rplanes, and the variation predicted through nebular evolutionarymodelling. This is used to suggest that observational biases areprobably modest, and that our revised distance scale is reasonablytrustworthy.
| Galactic Planetary Nebulae and their central stars. I. An accurate and homogeneous set of coordinates
We have used the 2nd generation of the Guide Star Catalogue (GSC-II) asa reference astrometric catalogue to compile the positions of 1086Galactic Planetary Nebulae (PNe) listed in the Strasbourg ESO Catalogue(SEC), its supplement and the version 2000 of the Catalogue of PlanetaryNebulae. This constitutes about 75% of all known PNe. For these PNe, theones with a known central star (CS) or with a small diameter, we havederived coordinates with an absolute accuracy of ~0\farcs35 in eachcoordinate, which is the intrinsic astrometric precision of the GSC-II.For another 226, mostly extended, objects without a GSC-II counterpartwe give coordinates based on the second epoch Digital Sky Survey(DSS-II). While these coordinates may have systematic offsets relativeto the GSC-II of up to 5 arcsecs, our new coordinates usually representa significant improvement over the previous catalogue values for theselarge objects. This is the first truly homogeneous compilation of PNepositions over the whole sky and the most accurate one available so far.The complete Table \ref{tab2} is only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/408/1029}
| Angular dimensions of planetary nebulae
We have measured angular dimensions of 312 planetary nebulae from theirimages obtained in Hα (or Hα + [NII]). We have appliedthree methods of measurements: direct measurements at the 10% level ofthe peak surface brightness, Gaussian deconvolution and second-momentdeconvolution. The results from the three methods are compared andanalysed. We propose a simple deconvolution of the 10% levelmeasurements which significantly improves the reliability of thesemeasurements for compact and partially resolved nebulae. Gaussiandeconvolution gives consistent but somewhat underestimated diameterscompared to the 10% measurements. Second-moment deconvolution givesresults in poor agreement with those from the other two methods,especially for poorly resolved nebulae. From the results of measurementsand using the conclusions of our analysis we derive the final nebulardiameters which should be free from systematic differences between small(partially resolved) and extended (well resolved) objects in our sample.Table 1 is only available in electronic form athttp://www.edpsciences.org
| Ionized haloes in planetary nebulae: new discoveries, literature compilation and basic statistical properties
We present a comprehensive observational study of haloes aroundplanetary nebulae (PNe). Deep Hα+[NII] and/or [OIII] narrow-bandimages have been obtained for 35 PNe, and faint extended haloes havebeen newly discovered in the following 10 objects: Cn 1-5, IC 2165, IC2553, NGC 2792, NGC 2867, NGC 3918, NGC 5979, NGC 6578, PB 4, andpossibly IC 1747. New deep images have also been obtained of other knownor suspected haloes, including the huge extended emission around NGC3242 and Sh 2-200. In addition, the literature was searched, andtogether with the new observations an improved data base containing some50 PN haloes has been compiled.The halo sample is illustrated in an image atlas contained in thispaper, and the original images are made available for use by thescientific community at http://www.ing.iac.es/~rcorradi/HALOES/.The haloes have been classified following the predictions of modernradiation-hydrodynamical simulations that describe the formation andevolution of ionized multiple shells and haloes around PNe. According tothe models, the observed haloes have been divided into the followinggroups: (i) circular or slightly elliptical asymptotic giant branch(AGB) haloes, which contain the signature of the last thermal pulse onthe AGB; (ii) highly asymmetrical AGB haloes; (iii) candidaterecombination haloes, i.e. limb-brightened extended shells that areexpected to be produced by recombination during the late post-AGBevolution, when the luminosity of the central star drops rapidly by asignificant factor; (iv) uncertain cases which deserve further study fora reliable classification; (v) non-detections, i.e. PNe in which no halois found to a level of <~10-3 the peak surface brightnessof the inner nebulae.We discuss the properties of the haloes: detection rate, morphology,location of the central stars in the Hertzsprung-Russell diagram, sizes,surface brightness profiles, and kinematical ages. Among the mostnotable results, we find that, as predicted by models, ionized AGBhaloes are a quite common phenomenon in PNe, having been found in 60 percent of elliptical PNe for which adequately deep images exist. Another10 per cent show possible recombination haloes. In addition, using thekinematical ages of the haloes and inner nebulae, we conclude that mostof the PNe with observed AGB haloes have left the AGB far from a thermalpulse, at a phase when hydrogen burning is the dominant energy source.We find no significant differences between the AGB haloes ofhydrogen-poor and hydrogen-rich central stars.
| The dust content of planetary nebulae: a reappraisal
We have performed a statistical analysis using broad band IRAS data onabout 500 planetary nebulae with the aim of characterizing their dustcontent. Our approach is different from previous studies in that it usesan extensive grid of photoionization models to test the methods forderiving the dust temperature, the dust-to-gas mass ratio and theaverage grain size. In addition, we use only distance independentdiagrams. With our models, we show the effect of contamination by atomiclines in the broad band IRAS fluxes during planetary nebula evolution.We find that planetary nebulae with very different dust-to-gas massratios exist, so that the dust content is a primordial parameter for theinterpretation of far infrared data of planetary nebulae. In contrastwith previous studies, we find no evidence for a decrease in thedust-to-gas mass ratio as the planetary nebulae evolve. We also showthat the decrease in grain size advocated by Natta & Panagia(\cite{NattaPanagia}) and Lenzuni et al. (\cite{Lenzuni}) is an artefactof their method of analysis. Our results suggest that the timescale fordestruction of dust grains in planetary nebulae is larger than theirlifetime. Table~1 is only accessible in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Abundance gradients in the outer galactic disk from planetary nebulae
Radial abundance gradients of the element ratios O/H, Ne/H, S/H, andAr/H are determined on the basis of a sample of disk planetary nebulae.The behaviour of the gradients at large distances from the galacticcentre, R > R_0 = 7.6 kpc, is emphasized. It is concluded that thederived gradients are consistent with an approximately constant slope inthe inner parts of the Galaxy, and some flattening for distances largerthan R_0. A comparison is made with previous determinations using bothphotoionized nebulae and young stars, and some consequences ontheoretical models for the chemical evolution of the galactic disk arediscussed. Table~1 is available only electronically at the CDS(anonymousftp 130.79.128.5 or http://cdsweb.u-strasbg.fr/Abstract.html)
| An atlas of images of Planetary Nebulae
A catalogue of narrowband CCD images of 100 southern and 1 northernPlanetary Nebulae is presented. The data are images taken in the lightof the Hα , Hβ , [OIII]500.7 nm, and [NII]658.4 nm lines. Foreach image we give the exposure time, the maximum extent of the nebula,and the seeing measured from the frames themselves. For ease ofreference, we have added an alphabetical list of the objects. Our listwill be useful for morphological studies of Planetary Nebulae, and iscomplementary to previously published lists, especially the one of\cite[Schwarz et al. (1992)]{sch92}. Based on observations obtained atthe European Southern Observatory, La Silla, Chile.
| Detection of new emission structures around planetary nebulae
Deep monochromatic observations are presented for 22 galactic planetarynebulae (PNe) performed through narrow-band interference filters, in thedirect imaging mode with i) the New Zealand (MJUO) f/7.8 Mc-Lellantelescope, ii) the Observatoire de Haute Provence (OHP) f/6 120-cmtelescope, and iii) and the Siding Spring Observatory (SSO) ATT 2.3metre telescope. Some of them are observed for the first time.Conspicuous secondary structures are detected far around theconventional nebular pictures. Such features could be relics of earlymass ejections during the post-AGB phase of the progenitors.Alternatively, they are more plausibly projections of externalloops/bubbles of the ``bar-bell'' shape upon the waist (for face-onPNe). We suggest that such structures (cf. Sh 1-89, Hua 1997) areintrinsic to all PNe. Their apparently diverse morphologies would``simply'' result from projections of a same PN intrinsic structure atdifferent view angles onto the plane of sky and with respect to themajor axis as well. In addition we report the detection of a new nebulain the field of NGC 3699 (50'' distant). Absolute fluxes are providedfor three emission lines. The observations were carried out at theSiding Spring Observatory operated by the Australian NationalUniversity, Australia. NGC 6853 was observed at the Haute ProvenceObservatory-CNRS 1.20-m telescope, France.
| The kinematics of 867 galactic planetary nebulae
We present a compilation of radial velocities of 867 galactic planetarynebulae. Almost 900 new measurements are included. Previously publishedkinematical data are compared with the new high-resolution data toassess their accuracies. One of the largest samples in the literatureshows evidence for a systematic velocity offset. We calculate weightedaverages between all available data. Of the final values in thecatalogue, 90% have accuracies better than 20 km s(-1) . We use thiscompilation to derive kinematical parameters of the galacticdifferential rotation obtained from least-square fitting and toestablish the Disk rotation curve; we find no significal trend for thepresence of an increasing external rotation curve. We examine also therotation of the bulge; the derived curve is consistent with a linearlyincreasing rotation velocity with l: we find V_b,r=(9.9+/-1.3)l -(6.7+/-8.5) km s(-1) . A possible steeper gradient in the innermostregion is indicated. Table 2 is available in electronic form only, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The molecular envelopes of planetary nebulae.
We report the results of a survey of millimeter CO emission in 91planetary nebulae using the IRAM 30 m and SEST 15 m telescopes. Theobservations provide new detections or improved data for 23 nebulae inthe CO(2-1) and/or CO(1-0) line, and sensitive limits for those not seenin CO. Analysis of the results together with previous observationsconfirms the existence of an important class of planetary nebulae withmassive (10^-2^-a few M_sun__) envelopes of molecular gas.These nebulae typically have abundance ratios of N/O>0.3 and bipolarmorphologies indicative of a young disk population. The column densitythrough the envelopes and their mass relative to the mass of ionized gasshow dramatic decreases with increasing nebular size, documenting theexpansion of the envelopes and the growth of the optical nebulae at theexpense of the molecular gas. The molecular envelopes remain a majormass component in these objects until the nebulae reach a radius ofR=~0.1pc. The nebulae not detected in CO have little or no molecular gas(<~10^-2^-10^-3^Msun_), and their envelopes must berapidly photo-dissociated before or during the compact phase. The largedifferences in the molecular gas content of the nebulae highlight thedifferent evolutionary paths for planetary nebula formation which resultfrom the range in mass of the progenitors and the structure of theircircumstellar envelopes.
| New abundances of southern planetary nebulae.
As a continuation of a long-term observational program with the purposeof deriving the chemical abundances of southern planetary nebulae (PN),we present here the line fluxes, colour excesses, electron temperaturesand densities, and abundances of He, O, N, S, Ar and Ne for 15 PN. Theseobjects were classified according to the Peimbert classification scheme,taking into account the chemical and kinematical properties as well asdistance-independent correlations.
| A statistical distance scale for Galactic planetary nebulae
A statistical distance scale is proposed. It is based on the correlationbetween the ionized mass and the radius and the correlation between theradio continuum surface brightness temperature and the nebular radius.The proposed statistical distance scale is an average of the twodistances obtained while using the correlation. These correlations,calibrated based on the 1`32 planetary nebulae with well-determinedindividual distances by Zhang, can reproduce not only the averagedistance of a sample of Galactic Bulge planetary nebulae exactly at thedistance to the Galactic center, but also the expected Gaussiandistribution of their distances around the Galactic center. This newdistance scale is applied to 647 Galactic planetary nebulae. It isestimated that this distance scale can be accurate on average to35%-50%. Our statistical distance scale is in good agreement with theone recently proposed by Van de Steene and Zijlstra. The correlationsfound in this study can be attributed to the fact that the core mass ofthe central stars has a very sharp distribution, strongly peaked atapprox. 0.6 solar mass. We stress that the scatter seen in thestatistical distance scale is likely to be real. The scatter is causedby the fact that the core mass distribution, although narrow andstrongly peaked, has a finite width.
| On an alternative statistical distance scale for planetary nebulae. Catalog with statistical distances to planetary nebulae.
We have proposed a statistical method to determine distances toplanetary nebulae. The method is based on an empirical correlationbetween the radio-continuum brightness temperature and radius. Here wepresent a catalog of distance determinations calculated using thismethod.
| Spectroscopic verification of suspected planetary nebulae, 3
Classification of eight objects as planetary nebulae was confirmedaccording to our image tube spectra; as to further two objects theirstatus remains unclear. We give estimates of line-strengths, derivedheliocentric radial velocities and their standard deviations.
| A catalogue HeII 4686 line intensities in Galactic planetary nebulae.
We have compiled the intensities of the HeII 4686 lines measured inGalactic planetary nebulae. We present a few observational diagramsrelated to this parameter, and discuss them with the help of theoreticaldiagrams obtained from simple model planetary nebulae surroundingevolving central stars of various masses. We determine the hydrogen andhelium Zanstra temperature for all the objects with accurate enoughdata. We argue that, for Galactic planetary nebulae as a whole, the maincause for the Zanstra discrepancy is leakage of stellar ionizing photonsfrom the nebulae.
| Trace of planetary nebula evolution by distance-independent parameters
Using existing infrared and radio data on a sample of 432 planetarynebulae, we derived a number of distance-independent parameters forcomparison with evolutionary models of planetary nebulae. We find thatmany of the observed properties of planetary nebulae can be explained bycurrent central star evolutionary models, even if the time scales aresubject to significant change by a factor of up to an order ofmagnitude. Specifically, we find that the evolutionary tracks are wellseparated in the radio surface brightness-central star temperatureplane, therefore allowing us to determine the core mass of individualplanetary nebulae. We also obtain the luminosity and gravity of thecentral stars of individual nebulae, from their temperature and coremass, without relying on the distance assumptions. We find that ourresults of the core mass are in good agreement with those of Mendez etal. (1992) and Tylenda et al. (1991). A systematic, large discrepancy isfound between the luminosity found in this work and that found byGathier and Pottasch (1986).
| The extinction constants for galactic planetary nebulae
The extinction constants are determined from Balmer decrementmeasurements for over 900 planetary nebulae. Comparison with publishedextinction constants shows that the results from ESO are fairlyreliable. An analysis of the extinction constants derived from theBalmer decrement and from the radio/Hβ flux ratio indicates thatthe latter tends to be systematically smaller than the former forincreasing extinction. We suggest that the radio measurements ofPottasch's group probably underestimate the radio fluxes, at least forsome (faintest) objects.
| A catalogue of absolute fluxes and distances of planetary nebulae
The paper presents a complete list of averaged recalibrated absoluteH-beta fluxes, global (where possible) relative He II lambda 4686fluxes, 5 GHz radio flux densities, and H-alpha/H-beta interstellarextinction constants for 778 Galactic planetary nebulae. The catalogprovides much of the fundamental data required to generate Zanstratemperatures. When data with the lowest errors are selected, the opticaland radio/optical extinctions show a peculiar correlation, with theradio values slightly high at low extinction and notably low at highextinction. The data are used, along with the best estimates of angulardiameters, to calculate Shklovsky distances according to the Daub schemeon the scale used earlier by Cahn and Kaler (1971). Use of this distancescale shows approximate equality of the death rates of optically thickand optically thin planetary nebulae. The method gives the correctdistances to the Magellanic Clouds.
| Strasbourg - ESO catalogue of galactic planetary nebulae. Part 1; Part 2
Not Available
| The absolute H-beta fluxes for galactic planetary nebulae
The absolute H-beta flux measurements from spectrophotometricobservations of about 880 galactic planetary nebulae are presented. Thegalactic coordinates of PNe and the adopted diameters for the nebulae inarcsec are given. The final values of the H-beta flux, corrected for thenebular extension, are presented and compared to the results of othermeasurements.
| The energy-balance temperature of central stars of galactic planetary nebulae. II
The color temperature of the central star of planetary nebulae iscalculated using data from the ongoing spectroscopic survey of galacticplanetary nebulae carried out by Acker and Stenholm in conjunction withan energy-balance (EB) method of Preite-Martinez and Pottasch (1983). Inthese calculations it was assumed that thermal equilibrium holds in thephotoionization nebula. The derived EB temperatures are found to beconsistent with the corresponding temperatures derived by the Zanstra(1931) method. The T(EB) values derived for six planetary nebulae alsoagree with those of Preite-Martinez and Pottasch.
| Winds in Central Stars of Planetary Nebulae
Not Available
| Central star temperatures of optically thick planetary nebulae and a distance-independent test of dredge-up theory
The effective temperatures are calculated and the V magnitudes arepredicted for the central stars of 62 optically thick planetary nebulasby forcing agreement between the hydrogen and ionized helium Zanstratemperatures. Comparison to the measured V for 34 of the stars showsgood agreement and validates the method for the other 28, for which noZanstra analysis is available. In many cases the predicted V magnitudesare actually likely to be better than the currently measured values. Thecomparison suggests that optical depth and not an ultraviolet excess isthe dominant cause of the Zanstra discrepancy. Nebular N/O correlatespositively with effective temperature, demonstrating that the N/O-coremass relation rises more steeply than predicted by dredge-up theory.
| Properties and evolution of dust grains in planetary nebulae
The IRAS data of 233 planetary nebulae (PNs) determining the propertiesof the dust contained in their envelopes have been analyzed. The mainresult is that the dust grains undergo substantial evolution during thelifetime of a PN. In particular, the grain size and the total dust massdecrease systematically with the nebular radius whereas the number ofemitting grains increases. Two scenarios which can explain these resultsare discussed. A first possibility is that grains undergo processeswhich both 'erode' and 'shatter' them. It is argued that sputtering byfast atoms of a stellar wind and grain-grain collisions may plausiblyproduce such effects. Alernatively, the dust present in PNs may have asize distribution since the very beginning and large grains may beselectively destroyed during the PN evolution.
| A catalogue of expansion velocities of Galactic planetary nebulae
Published observational data on 288 Galactic PN are compiled in tables,graphs, and sketches based on spatiokinematical models and brieflycharacterized. The criteria used in selecting the data are discussed,and particular attention is given to the accuracies of the distanceestimates and their implications for theoretical models of PN or stellarevolution.
| Planetary nebulae in the Galaxy
It is shown that the planetary nebulae can be divided into three typesaccording to the values of the mass of shell and a central star. Thecriteria are given using which one can determine the mass type of thenebula. The distance scale of each mass-type planetary nebulae is given.The distribution of planetary nebulae in the Galaxy, their formationrate, scale-height and other physical and kinematic characteristics areinvestigated. A catalogue of planetary nebulae emitting in the ratiorange is given.
| Apparent magnitudes of luminous planetary nebula nuclei. II - A survey of southern hemisphere planetary nebulae
Narrow-band continuum and emission-line photometry of 145 southernhemisphere PN are presented. Total fluxes in the important nebular linesHe II 4686 A, H-beta, forbidden O III 4959, H-alpha, and forbidden N II6583 A are measured and used to determine the nebular distances andionizations, interstellar reddenings, and He(2+) abundances and toderive the luminosities and temperatures of the central stars. The linefilter data and the stellar continuum magnitudes are compared in detailwith those from other authors and with magnitudes derived fromnarrow-band imaging. The luminosities and effective temperatures ofthose PN nuclei for which sufficient and reliable data exist arecalculated.
| The systematics and distribution of molecular hydrogen in planetary nebulae
Twenty-two planetary nebulae have been searched for the infrared linesof excited molecular hydrogen, and strong H2 lines have been detectedand imaged in 11 of these. From these and published data, it has beendemonstrated that all planetaries with strong excited molecular hydrogenbelong to a particular subclass of the Type I planetary nebulae. Thissubclass is characterized morphologically by an equatorial toroid withfaint bipolar extensions. Furthermore, nearly all planetaries with thesecharacteristics have strong molecular lines. In most cases, thedistribution of the excited H2 lines is indistinguishable from the redimages which delineate singly ionized nitrogen (and ionized hydrogen),suggesting that the emitting molecules lie close to the transitionregion between ionized and neutral gas. If the excitation is by shocks,which is consistent with the line ratios and the distribution, then theobservations suggest that the morphology of these planetaries has beencontrolled by a fast stellar wind interacting with a disk of gasconcentrated in the equatorial plane.
| A study of some southern planetary nebulae
Radial velocities and expansions velocities (forbidden line O III,forbidden line O II, and He II) are measured for a sample of 64 southernGalactic planetary nebulae. Also, nebular electronic densities arederived from the forbidden line O II 3727, 3729 A double for 23 of theseobjects. The distance scale of Dopita et al. (1987) is used to derivedistances to 33 Galactic nebulae.
| Radio and infrared structures of type I post-main sequence nebulae
High-resolution VLA radio mapping at 1.46, 4.84, and 15.0 GHz ispresented together with NIR J,H,K,L, and M mapping and photometry of abroad range of type I postmain-sequence nebulae. Many of these sourceshave extremely compact infrared and radio cores ranging from 0.1 to 0.01pc in size; in some cases they contain up to 96 percent of the totalradio flux. A detailed investigation of the IRAS photometry for type Inebulae was undertaken; a typical interior grain temperature isestimated to be 200 K while outer shell temperatures are estimated to beless than 50 K.
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