Galactic Bulge Planetary Nebulae Research Articles

Chemical abundances of planetary nebulae from optical recombination lines - III. The Galactic bulge PN M 1-42 and M 2-36

We present deep, high-resolution optical spectra of two Galactic bulge planetary nebulae (PN), M 1-42 and M 2-36. The spectra show very prominent and rich optical recombination lines (ORLs) from C, N, O and Ne ions. Infrared spectra from were also obtained using the Short and Long Wavelength Spectrometer (SWS and LWS) on board ISO. The optical and infrared spectra, together with archival IUE spectra, are used to study their density and thermal characteristics and to determine elemental abundances. We determine the optical and UV extinction curve towards these two bulge PN using observed H i and He ii recombination line fluxes and the radio free–free continuum flux density. In the optical, the reddening curve is found to be consistent with the standard Galactic extinction law, with a total to selective extinction ratio . However, the extinction in the UV is found to be much steeper, consistent with the earlier finding of Walton, Barlow & Clegg. The rich ORL spectra from C, N, O and Ne ions detected from the two nebulae have been used to determine the abundances of these elements relative to hydrogen. In all cases, the resultant ORL abundances are found to be significantly higher than the corresponding values deduced from collisionally excited lines (CELs). In M 2-36, the discrepancies are about a factor of 5 for all four elements studied. In M 1-42, the discrepancies reach a factor of about 20, the largest ever observed in a PN. M 1-42 also has the lowest Balmer jump temperature ever determined for a PN, , 5660 K lower than its [O iii] forbidden line temperature. We compare the observed intensities of the strongest O ii ORLs from different electronic configurations, including λ4649 from , λ4072 from , λ4089 from , and λ4590 and λ4190 from the doubly excited and configurations, respectively. In all cases, in spite of the fact that the ratios of the ORL to CEL ionic abundances span a wide range from ∼, the intensity ratios of λ4649, λ4072, λ4590 and λ4190 relative to λ4089 are found to be nearly constant, apart from some small monotonic increase of these ratios as a function of electron temperature. Over a range of Balmer jump temperature from , the variations amount to about 20 per cent for the and transitions and a factor of 2 for the primed transitions, and are consistent with the predictions of the current recombination theory. Our results do not support the claim by Dinerstein, Lafon & Garnett that the relative intensities of O ii ORLs vary from nebula to nebula and that the scatter is largest in objects where the discrepancies between ORL and CEL abundances are also the largest. We find that the ORL to CEL abundance ratio is highly correlated with the difference between the temperatures yielded by the [O iii] forbidden line ratio and by the H i Balmer jump, providing the strongest evidence so far that the two phenomena, i.e. the disparity between ORL and CEL temperature and abundance determinations, are closely related. However, temperature fluctuations of the type envisaged by Peimbert are unable to explain the low ionic abundances yielded by IR fine-structure lines. The very low Balmer jump temperature of M 1-42, coupled with its very low Balmer decrement density, may also be difficult to explain with a chemically inhomogeneous composite model of the type proposed by Liu et al. for NGC 6153.

An analysis of the observed radio emission from planetary nebulae

We have analysed the radio fluxes for 264 planetary nebulae for which reliable measurements of fluxes at 1.4 and 5 GHz, and of nebular diameters are available. For many of the investigated nebulae the optical thickness is important, especially at 1.4 GHz. Simple models like the one specified only by a single optical thickness or spherical, constant density shells do not account satisfactorily for the observations. Also an r^{-2} density distribution is ruled out. A reasonable representation of the observations can be obtained by a two-component model having regions of two different values of optical thickness. We show that the nebular diameters smaller than 10 arcsec are uncertain, particularly if they come from photographic plates or gaussian fitting to the radio profile. While determining the interstellar extinction from an optical to radio flux ratio caution should be paid to optical thickness effects in the radio. We have developed a method for estimating the value of self absorption. At 1.4 GHz self absorption of the flux is usually important and can exceed a factor of 10. At 5 GHz self absorption is negligible for most of the objects although in some cases it can reach a factor of 2. The Galactic bulge planetary nebulae when used to calibrate the Shklovsky method give the mean nebular mass of 0.14 solar mass. The statistical uncertainty of the Shklovsky distances is smaller than factor 1.5.

Radio observations of new galactic bulge planetary nebulae

We observed 64 newly identified galactic bulge planetary nebulae in the radio continuum at 3 and 6 cm with the Australia Telescope Compact Array. We present their radio images, positions, flux densities, and angular sizes. The survey appears to have detected a larger ratio of more extended planetary nebulae with low surface brightness than in previous surveys. We calculated their distances according to Van de Steene & Zijlstra (1995). We find that most of the new sample is located on the near side around the galactic center and closer in than the previously known bulge PNe. Based on H-alpha images and spectroscopic data, we calculated the total H-alpha flux. We compare this flux value with the radio flux density and derive the extinction. We confirm that the distribution of the extinction values around the galactic center rises toward the center, as expected.

8-13 m dust emission features in Galactic bulge planetary nebulae

The definitive version is available at www.blackwell-synergy.com '. Copyright Blackwell Publishing. DOI : 10.1046/j.1365-8711.2001.04750.x

PNe Abundances: Galactic Bulge Versus the Disc

We compare the abundances of He, N, O, Ar, S, and Ne, determined in a similar way, for a sample of Galactic bulge and disc planetary nebulae (PNe). We find that in all aspects – average abundances and dispersion, distribution functions, abundance relationships, and the ratio of N/O – the bulge and disc PNe are indistinguishable. The nebular distribution of [O/H] is different to the stellar.

Photoionization modelling of planetary nebulae -- II. Galactic bulge nebulae, a comparison with literature results

We have constructed photoionization models of five galactic bulge planetary nebulae using our automatic method, which enables a fully self-consistent determination of the physical parameters of a planetary nebula. The models are constrained using the spectrum, the IRAS and radio fluxes and the angular diameter of the nebula. We also conducted a literature search for physical parameters determined with classical methods for these nebulae. Comparison of the distance-independent physical parameters with published data shows that the stellar temperatures generally are in good agreement and can be considered reliable. The literature data for the electron temperature, electron density and also for the abundances show a large spread, indicating that the use of line diagnostics is not reliable and that the accuracy of these methods needs to be improved. Comparison of the various abundance determinations indicates that the uncertainty in the electron temperature is the main source of uncertainty in the abundance determination. The stellar magnitudes predicted by the photoionization models are in good agreement with observed values.

The features of infra-red emission of the galactic bulge planetary nebulae

Abstract 302 planetary nebulae located within the sector of galactic longitudes from 345° to 15° have been investigated. All nebulae have been subdivided into four mass classes and different distance scales for each class have been used. Planetary nebulae located within the galactic bulge have been selected. The galactic radial gradients of infra-red luminosities and excesses are obtained for each nebula mass class. Possible explanations of the effect are discussed.

A statistical distance scale for Galactic planetary nebulae

view Abstract Citations (197) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Statistical Distance Scale for Galactic Planetary Nebulae Zhang, C. Y. Abstract A statistical distance scale is proposed. It is based on the correlation between the ionized mass and the radius and the correlation between the radio continuum surface brightness temperature and the nebular radius. The proposed statistical distance scale is an average of the two distances obtained while using the correlation. These correlations, calibrated based on the 1`32 planetary nebulae with well-determined individual distances by Zhang, can reproduce not only the average distance of a sample of Galactic Bulge planetary nebulae exactly at the distance to the Galactic center, but also the expected Gaussian distribution of their distances around the Galactic center. This new distance scale is applied to 647 Galactic planetary nebulae. It is estimated that this distance scale can be accurate on average to 35%-50%. Our statistical distance scale is in good agreement with the one recently proposed by Van de Steene and Zijlstra. The correlations found in this study can be attributed to the fact that the core mass of the central stars has a very sharp distribution, strongly peaked at approx. 0.6 solar mass. We stress that the scatter seen in the statistical distance scale is likely to be real. The scatter is caused by the fact that the core mass distribution, although narrow and strongly peaked, has a finite width. Publication: The Astrophysical Journal Supplement Series Pub Date: June 1995 DOI: 10.1086/192173 Bibcode: 1995ApJS...98..659Z Keywords: Brightness; Brightness Distribution; Distance; Ionized Gases; Planetary Nebulae; Scale (Ratio); Statistical Correlation; Statistical Distributions; Galactic Bulge; Galactic Nuclei; Galactic Structure; Astrophysics; COSMOLOGY: DISTANCE SCALE; ISM: PLANETARY NEBULAE: GENERAL full text sources ADS | data products SIMBAD (644) CDS (2) Related Materials (1) Catalog: 1996yCat..20980659Z

Simulations of a Population of Planetary Nebulae

We present a simulation of the population of Galactic bulge planetary nebulae (GBPN), which matches the diagrams obtained from VLA radio observations. This simulation may not be the only one fitting the observed data, but it helps understanding the role of observational uncertainties and selection effects in the interpretation of observational diagrams.

Chemical Abundances in Galactic Bulge Pn

We present abundance determinations, in particular of carbon, and C/O ratios, for 11 Galactic bulge planetary nebulae (PN) based on our low resolution UV data from IUE observations and optical spectrophotometry from the Anglo-Australian Telescope. We compare the observed abundances with those predicted by dredge-up theory for the high metallicity Galactic bulge. The sample abundances are also contrasted with the abundances found for PN in the Galactic disk. The mean C/O ratio for the bulge PN is significantly lower than that found for Galactic disk PN. Further, we present an abundance analysis of the very metal-poor bulge PN M2-29. From an analysis of the differential extinction found from the observed ratios of the He ii 1640,4686Å lines, we find that the ultraviolet reddening law towards the bulge is steeper than in the solar neighbourhood.

Filling Factors and Ionized Masses of Planetary Nebulae

We present a study on the filling factors and ionized masses of four sets of galactic and extra–galactic planetary nebulae (PNe) at known distances. The calculation of filling factors and ionized masses has been pursued as to get a deeper insight on the evolution of this class of objects. We used a galactic set of PNe, another set of nebulae that are averagely located near the galactic center, and two sets of nebulae in the Magellanic Clouds. As input data, we used the electron densities derived from the forbidden line intensity ratios, the Hβ nebular fluxes, the distances of galactic PNe derived from extinction, and the distances of galactic center PNe and of extra–galactic PNe derived from galaxy (or galactic region) memberships. All these quantities, plus the input angular radii, have been selected among the most recent measurements available in the literature. We obtained several interesting results. (1) The calculated filling factors are on average much smaller than what is usually assumed, independently for each set. (2) The ionized masses are all in good agreement with the theoretical predictions, with the possible exception of the Galactic Bulge PNe. (3) Both filling factors and ionized masses cover a wide range of values as it is shown in the cumulative histograms below (filled circles=local PNe; open circles=galactic center PNe; filled squares=LMC PNe; open squares=SMC PNe).

High-resolution imaging and the H-R diagram of Galactic bulge planetary nebulae

Images of six Galactic PNe in the forbidden O III 5007 line obtained with unprecedented resolution are compared here with those obtained at radio wavelengths. A self-consistent photoionization model obtained using optical spectrophotometry is used to derive chemical abundances and to place the central stars on the H-R diagram. The results are similar to those obtained with the classical Zanstra technique, but with the advantage that objects with high or low temperature central stars can be studied with equal ease. A wide range of metallicity is found which shows that the objects currently passing through the PN phase in the Galactic bulge were born both during and after the collapse of the Galaxy.