Planetary nebulae and the chemical evolution of the Magellanic Clouds (original) (raw)
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Chemical evolution of the Magellanic Clouds based on planetary nebulae
2008
Planetary nebulae (PN) are an essential tool in the study of the chemical evolution of the Milky Way and galaxies of the Local Group, particularly the Magellanic Clouds. In this work, we present some recent results on the determination of chemical abundances from PN in the Large and Small Magellanic Clouds, and compare these results with data from our own Galaxy and other galaxies in the Local Group. As a result of our continuing long term program, we have a large database comprising about 300 objects for which reliable abundances of several elements from He to Ar have been obtained. Such data can be used to derive constraints to the nucleosynthesis processes in the progenitor stars in galaxies of different metallicities. We also investigate the time evolution of the oxygen abundances in the SMC by deriving the properties of the PN progenitor stars, which include their masses and ages. We have then obtained an age-metallicity relation taking into account both oxygen and [Fe/H] abundances. We show that these results have an important consequence on the star formation rate of the SMC, in particular by suggesting a star formation burst in the last 2-3 Gyr.
Chemical Composition of Planetary Nebulae: The Galaxy and the Magellanic Clouds
2006
An analysis is made of the abundances of planetary nebulae (PN) in the Galaxy (MW), the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). The data has been gathered by the IAG/USP group in a homogeneous procedure, involving observational techniques, data acquisition and reduction. Emphasis is placed on distance-independent correlations, which are particularly important for PN in the galactic disk. It is shown that (i) our abundances are comparable to the accurate abundances of nebulae with ISO data, (ii) most abundance correlations hold for all three systems, taking into account the metallicity differences between the Galaxy and the Magellanic Clouds, and (iii) there is a good general agreement of our data with the predictions of recent theoretical models for PN progenitors.
Chemical evolution of the Small Magellanic Cloud based on planetary nebulae
Astronomy & Astrophysics, 2008
Aims. We investigate the chemical evolution of the Small Magellanic Cloud (SMC) based on abundance data of planetary nebulae (PNe). The main goal is to investigate the time evolution of the oxygen abundance in this galaxy by deriving an age-metallicity relation. Such a relation is of fundamental importance as an observational constraint for chemical evolution models of the SMC. Methods. We have used high quality PNe data to derive the properties of the progenitor stars, so that the stellar ages could be estimated. We collected a large number of measured spectral fluxes for each nebula and derived accurate physical parameters and nebular abundances. New spectral data for a sample of SMC PNe obtained between 1999 and 2002 are also presented. These data are used with data available in the literature to improve the accuracy of the fluxes for each spectral line. Results. We obtained accurate chemical abundances for PNe in the SMC, which can be useful as tools in the study of the chemical evolution of this galaxy and of Local Group galaxies. We present the resulting oxygen-versus-age diagram and a similar relation involving the [Fe/H] metallicity based on a correlation with stellar data. We discuss the implications of the derived age-metallicity relation for the SMC formation, in particular by suggesting a star formation burst in the last 2-3 Gyr.
2004
Abstract. An analysis is made of the abundances of planetary nebulae (PN) in the Galaxy (MW), the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). The data has been gathered by the IAG/USP group in a homogeneous procedure, involving observational techniques, data acquisition and reduction. Emphasis is placed on distance-independent correlations, which are particularly important for PN in the galactic disk. It is shown that (i) our abundances are comparable to the accurate abundances of nebulae with ISO data, (ii) most abundance correlations hold for all three systems, taking into account the metallicity differences between the Galaxy and the Magellanic Clouds, and (iii) there is a good general agreement of our data with the predictions of recent theoretical models for PN progenitors. 1
The Astrophysical Journal, 2010
We present an analysis of elemental abundances of He, N, O, Ne, S, and Ar in Magellanic Cloud planetary nebulae (PNe), and focus initially on 14 PNe in the Small Magellanic Cloud (SMC). We derived the abundances from a combination of deep, high dispersion optical spectra, as well as mid-infrared (IR) spectra from the Spitzer Space Telescope. A detailed comparison with prior SMC PN studies shows that significant variations among authors of relative emission line flux determinations lead to systematic discrepancies in derived elemental abundances between studies that are 0.15 dex, in spite of similar analysis methods. We used ionic abundances derived from IR emission lines, including those from ionization stages not observable in the optical, to examine the accuracy of some commonly used recipes for ionization correction factors (ICFs). These ICFs, which were developed for ions observed in the optical and ultraviolet, relate ionic abundances to total elemental abundances. We find that most of these ICFs work very well even in the limit of substantially sub-Solar metallicities, except for PNe with very high ionization. Our abundance analysis shows enhancements of He and N that are predicted from prior dredge-up processes of the progenitors on the AGB, as
Nucleosynthesis and chemical evolution of intermediate mass stars: results from planetary nebulae
2010
Planetary nebulae (PN) are an excellent laboratory to investigate the nucleosynthesis and chemical evolution of intermediate mass stars. In these objects accurate abundances can be obtained for several chemical elements that are manufactured or contaminated by the PN progenitor stars, such as He, N, C, and also elements that were originally produced by more massive stars of previous generations, namely O, Ne, Ar, and S. Some of these elements are difficult to study in stars, so that PN can be used in order to complement results obtained from stellar data. In the past few years, we have obtained a large sample of PN with accurately derived abundances, including objects of different populations, namely the solar neighbourhood, the galactic disk and anticentre, the galactic bulge and the Magellanic Clouds. In this work, we present the results of our recent analysis of the chemical abundances of He, O, N, S, Ar and Ne in galactic and Magellanic Cloud PN. Average abundances and abundance distributions of all elements are determined, as well as distance-independent correlations. These correlations are particularly important, as they can be directly compared with the predictions of recent theoretical evolutionary models for intermediate mass stars.
The planetary nebulae populations in five galaxies: abundance patterns and evolution
Astronomy and …, 1998
We have collected photometric and spectroscopic data on planetary nebulae (PNe) in 5 galaxies: the Milky Way (bulge), M 31 (bulge), M 32, the LMC and the SMC. We have computed the abundances of O, Ne and N and compared them from one galaxy to another. In each Galaxy, the distribution of oxygen abundances has a large dispersion. The average O/H ratio is larger in the M 31 and the Galactic bulge PNe than in those in the Magellanic Clouds. In a given galaxy, it is also larger for PNe with [O III] luminosities greater than 100 L , which are likely to probe more recent epochs in the galaxy history. We find that the M 31 and the Galactic bulge PNe extend the very tight Ne/H-O/H correlation observed in the Galactic disk and Magellanic Clouds PNe towards higher metallicities. We note that the anticorrelation between N/O and O/H that was known to occur in the Magellanic Clouds and in the disk PNe is also marginally found in the PNe of the Galactic bulge. Furthermore, we find that high N/O ratios are higher for less luminous PNe. In M 32, all PNe have a large N/O ratio, indicating that the stellar nitrogen abundance is enhanced in this galaxy. We have also compared the PN evolution in the different galactic systems by constructing diagrams that are independent of abundances, and have found strikingly different behaviours of the various samples. In order to help in the interpretation of these data, we have constructed a grid of expanding, PN photoionization models in which the central stars evolve according to the evolutionary tracks of Blöcker (1995). These models show that the apparent spectroscopic properties of PNe are extremely dependent, not only on the central stars, but also on the masses and expansion velocities of the nebular envelopes. The main conclusion of the confrontation of the observed samples with the model grids is that the PN populations are indeed not the same in the various parent galaxies. Both stars and nebulae are different. In particular, the central stars of the Send offprint requests to: Stasińska Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http: //cdsweb.u-strasbg.fr/Abstract.html Magellanic Clouds PNe are shown to evolve differently from the hydrogen burning stellar evolutionary models of Blöcker (1995). In the Galactic bulge, on the other hand, the behaviour of the observed PNe is roughly compatible with the theoretical stellar evolutionary tracks. The case of M 31 is not quite clear, and additional observations are necessary. It seems that the central star mass distribution is narrower for the M 31 PNe than for the Galactic bulge PNe. We show that spectroscopy of complete samples of PNe down to a factor 100 below the maximum luminosity would help to better characterize the PN central star mass distribution.
Magellanic Cloud planetary nebulae as probes of stellar evolution and populations
The Local Group as an Astrophysical Laboratory
Nebulae (PNs) in the Magellanic Clouds offer the unique opportunity to study both the population and evolution of low-and intermediate-mass stars, in an environment that is free of the distance scale bias and the differential reddening that hinder the observations of the Galactic sample. The study of LMC and SMC PNs also offers the direct comparison of stellar populations with different metallicity. The relative proximity of the Magellanic Clouds allows detailed spectroscopic analysis of the PNs therein, while the Hubble Space Telescope (HST) is necessary to obtain their spatially-resolved images. In this paper we discuss the history and evolution of this relatively recent branch of stellar astrophysics by reviewing the pioneering studies, and the most recent ground-and space-based achievements. In particular, we present the results from our recent HST surveys, including the metallicity dependence of PN identification (and, ultimately, the metallicity dependence of PN counts in galaxies); the morphological analysis of Magellanic PNs, and the correlations between morphology and other nebular properties; the relations between morphology and progenitor mass and age; and the direct analysis of Magellanic central stars and their importance to stellar evolution. Our morphological results are broadly consistent with the predictions of stellar evolution if the progenitors of asymmetric PNs have on average larger masses than the progenitors of symmetric PNs, without any assumption or relation to binarity of the stellar progenitors.
Planetary nebulae as probes for galactic chemical evolution
Proceedings of the International Astronomical Union, 2006
The role of planetary nebulae as probes for the galactic chemical evolution is reviewed. Their abundances throughout the Galaxy are discussed for key elements, in particular oxygen and other alpha elements. The abundance distribution derived from planetary nebulae leads to the establishment of radial abundance gradients in the galactic disk that are important constraints to model the chemical evolution of the Galaxy. The radial gradient, well determined for the solar neighborhood, is examined for distinct regions. For the galactic anticenter in particular, the observational data confirm results from galactic evolution models that point to a decreasing in the gradient slope at large galactocentric distances. The possible time evolution of the radial gradient is also examined comparing samples of planetary nebulae of different ages, and the results indicate that a flattening in the gradient occurred, which is confirmed by some galactic evolution models. The galactic bulge is another important region whose modeling can be constrained by observational results obtained from planetary nebulae. Results derived in the last few years indicate that bulge nebulae have an abundance distribution similar to that of disk objects, however with a larger dispersion.