scholarly journals Abundance gradients: tracing the chemical properties of the disk

2009 ◽  
Vol 5 (H15) ◽  
pp. 790-790
Author(s):  
Roberto D.D. Costa ◽  
Walter J. Maciel
Keyword(s):  
Time Evolution ◽  
Chemical Evolution ◽  
Galactic Disk ◽  
Chemical Properties ◽  
Planetary Nebulae ◽  
Hii Regions ◽  
B Stars ◽  
Radial Gradient ◽  
The Galaxy ◽  
Vertical Gradients

AbstractAbundance gradients are key parameters to constrain the chemical evolution of the galactic disk. In this review recent determinations for the radial gradient are described, including its slope as derived from different objects such as planetary nebulae, HII regions, cepheids, or B stars, and for different elements. Inner and outer limits for the radial gradient, as well as its time evolution, both related to the chemical evolution of the Galaxy, are also described. The possible existence of azimuthal and vertical gradients is also discussed.

scholarly journals O, S, Ar from Planetary Nebulae Data and the Chemical Evolution of the Galactic Disk

1993 ◽  
Vol 155 ◽  
pp. 576-576
Author(s):  
J.A. De Freitas Pacheco
Keyword(s):  
Chemical Evolution ◽  
Galactic Disk ◽  
Planetary Nebulae ◽  
Hii Regions ◽  
Type Ia Supernovae ◽  
Type I ◽  
Intermediate Mass ◽  
B Stars ◽  
Type Ia ◽  
Ia Supernovae

The O, S, Ar abundances for a sample of 122 planetary nebulae (merging LNA data and those by Köppen, Acker and Stenholm 1991) were analysed. Average abundances were calculated for progenitors having different metallicities (ages). Our study suggests that type I planetaries, whose progenitors are not older than 1–2 Gyr, have average oxygen abundances 0.2 dex lower than the solar value. This agrees with O-abundance determinations in HII regions, intermediate mass supergiants and B stars in young associations. S and Ar show a different behaviour. We suggest that such a paucity of O in the ISM is produced by recent infalling gas from the halo, having abundance ratios similar to those expected from type Ia supernovae.

scholarly journals Abundance gradients from Planetary Nebulae in the galactic disk

1997 ◽  
Vol 180 ◽  
pp. 397-404 ◽  
Author(s):  
W.J. Maciel
Keyword(s):  
Chemical Evolution ◽  
Spiral Galaxies ◽  
Galactic Disk ◽  
Chemical Elements ◽  
Planetary Nebulae ◽  
Hii Regions ◽  
Additional Constraint ◽  
Established Fact ◽  
Metallicity Distribution

Radial abundance gradients in the disks of spiral galaxies are made evident from observations of ionized nebulae (HII regions, planetary nebulae, and SNRs) and stars. They have been observed for several chemical elements, and their presence is an established fact, despite some inconsistencies in the results. Therefore, these gradients can be considered as an additional constraint to the chemical evolution models, as the age-metallicity relation or the metallicity distribution of the G-dwarfs.

scholarly journals Some aspects of the chemical evolution of 4He in the Galaxy: the He/H radial gradient and the ΔY/ΔZ enrichment ratio

2000 ◽  
Vol 198 ◽  
pp. 204-213
Author(s):  
W. J. Maciel
Keyword(s):  
Chemical Evolution ◽  
Heavy Element ◽  
Planetary Nebulae ◽  
Enrichment Ratio ◽  
Radial Gradient ◽  
The Galaxy ◽  
Element Enrichment ◽  
Progenitor Stars

Two aspects of the chemical evolution of 4He in the Galaxy are considered on the basis of a sample of disk planetary nebulae by the application of corrections due to the contamination of 4He from the progenitor stars. First, the He/H radial gradient is analyzed, and then, the helium to heavy element enrichment ratio is determined for metallicities up to the solar value.

scholarly journals Non-LTE Abundances in OB stars: Preliminary Results for 5 Stars in the Outer Galactic Disk

2014 ◽  
Vol 9 (S307) ◽  
pp. 90-91
Author(s):  
G. A. Bragançca ◽  
T. Lanz ◽  
S. Daflon ◽  
K. Cunha ◽  
C. D. Garmany ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Galactic Disk ◽  
B Stars ◽  
Large Sample ◽  
Ob Stars ◽  
Preliminary Results ◽  
Elemental Abundances ◽  
The Galaxy ◽  
Ionization Equilibria ◽  
Chemical Distribution

AbstractThe aim of this study is to analyse and determine elemental abundances for a large sample of distant B stars in the outer Galactic disk in order to constrain the chemical distribution of the Galactic disk and models of chemical evolution of the Galaxy. Here, we present preliminary results on a few stars along with the adopted methodology based on securing simultaneous O and Si ionization equilibria with consistent NLTE model atmospheres.

scholarly journals Planetary nebulae and determination of the bulge–disk boundary

2012 ◽  
Vol 8 (S289) ◽  
pp. 375-378
Author(s):  
Roberto D. D. Costa ◽  
Oscar Cavichia ◽  
Walter J. Maciel
Keyword(s):  
Galactic Center ◽  
Chemical Properties ◽  
Planetary Nebulae ◽  
Galactocentric Distance ◽  
Disk Interface ◽  
Radial Gradient ◽  
Element Abundances ◽  
Outer Component ◽  
The Galaxy ◽  
Kolmogorov Smirnov

AbstractIn this paper, a sample of planetary nebulae in the Galaxy's inner-disk and bulge is used to find the galactocentric distance that optimally separates these two populations in terms of their abundances. Statistical distance scales were used to investigate the distribution of abundances across the disk–bulge interface, while a Kolmogorov–Smirnov test was used to find the distance at which the chemical properties of these regions separate optimally. The statistical analysis indicates that, on average, the inner population is characterized by lower abundances than the outer component. Additionally, for the α-element abundances, the inner population does not follow the disk's radial gradient toward the Galactic Center. Based on our results, we suggest a bulge–disk interface at 1.5 kpc, marking the transition between the bulge and the inner disk of the Galaxy as defined by the intermediate-mass population.

scholarly journals The Evolution of 3He, 4He and D in the Galaxy

2000 ◽  
Vol 198 ◽  
pp. 540-546 ◽  
Author(s):  
Cristina Chiappini ◽  
Francesca Matteucci
Keyword(s):  
Chemical Evolution ◽  
Present Model ◽  
Galactic Disk ◽  
The Sun ◽  
Mixing Process ◽  
Low Mass Stars ◽  
A Value ◽  
The Galaxy ◽  
Low Mass ◽  
Standing Problem

In this work we present the predictions of a modified version of the ‘two-infall model’ (Chiappini et al. 1997 - CMG) for the evolution of 3He, 4He and D in the solar vicinity, as well as their distributions along the Galactic disk. In particular, we show that when allowing for extra-mixing process in low mass stars (M < 2.5 M⊙), as predicted by Charbonnel and do Nascimento (1998), a long standing problem in chemical evolution is solved, namely: the overproduction of 3He by the chemical evolution models as compared to the observed values in the sun and in the interstellar medium. Moreover, we show that chemical evolution models can constrain the primordial value of the deuterium abundance and that a value of (D/H)p < 3 × 10—5 is suggested by the present model. Finally, adopting the primordial 4He abundance suggested by Viegas et al. (1999), we obtain a value for ΔY/ΔZ ≃ 2 and a better agreement with the solar 4He abundance.

scholarly journals Interstellar and Stellar Abundances Across the Galactic Disk

1977 ◽  
Vol 45 ◽  
pp. 149-159 ◽  
Author(s):  
Manuel Peimbert
Keyword(s):  
Chemical Composition ◽  
Density Distribution ◽  
Chemical Evolution ◽  
Galactic Disk ◽  
Theoretical Models ◽  
Observational Evidence ◽  
Stellar Abundances ◽  
Abundance Gradient ◽  
The Galaxy

Abstract.Observational evidence related to the chemical composition across the disk of the Galaxy is reviewed. The H2density distribution derived for the Galaxy is poorly known, consequently it is still not possible to compare theoretical models of the chemical evolution of the Galaxy with the gaseous density distribution. The H2density distribution is particularly sensitive to the fraction of carbon atoms embedded in CO molecules and to the possible presence of a C/H abundance gradient.

scholarly journals Chemical evolution of bulges at high redshift

2007 ◽  
Vol 3 (S245) ◽  
pp. 19-22
Author(s):  
Antonio Pipino ◽  
Francesca Matteucci ◽  
Annibale D'Ercole
Keyword(s):  
Chemical Evolution ◽  
High Redshift ◽  
Chemical Properties ◽  
Elliptical Galaxies ◽  
Gas Flows ◽  
Apparent Lack ◽  
Hydrodynamical Models ◽  
Radial Gradient ◽  
New Class ◽  
The Mean

AbstractWe present a new class of hydrodynamical models for the formation of bulges (either massive elliptical galaxies or classical bulges in spirals) in which we implement detailed prescriptions for the chemical evolution of H, He, O and Fe. Our results hint toward an outside-in formation in the context of the supernovae-driven wind scenario. The build-up of the chemical properties of the stellar populations inhabiting the galactic core is very fast. Therefore we predict a non significant evolution of both the mass-metallicity and the mass-[α/Fe] relations after the first 0.5 − 1 Gyr. In this framework we explain how the observed slopes, either positive or negative, in the radial gradient of the mean stellar [α/Fe], and their apparent lack of any correlation with all the other observables, can arise as a consequence of the interplay between star formation and metal-enhanced internal gas flows.

scholarly journals Planetary Nebulae: A Probe of the Galaxies Evolution up to the Hubble Time

2006 ◽  
Vol 2 (S235) ◽  
pp. 324-324
Author(s):  
A. F. Kholtygin ◽  
Yu. V. Milanova
Keyword(s):  
Chemical Evolution ◽  
Planetary Nebulae ◽  
Early Age ◽  
The Galaxy ◽  
Galactic Abundance ◽  
Progenitor Stars ◽  
Hubble Time

Chemical evolution of the galactic and extragalactic planetary nebulae (PNe) system beginning from the early age of the Galaxy is investigated. We determine the radial and vertical abundance gradients for C, N, O, Ne, Ar, Cl and S in a dependence on mass and age of the progenitor stars of the nebula. In the Table 1 we compare the galactic abundance gradients for O and Ne for our and neigbour galaxies.

scholarly journals Chemical Evolution of the Galactic Disk and the Radial Metallicity Gradient

1976 ◽  
Vol 72 ◽  
pp. 207-208
Author(s):  
M. Mayor
Keyword(s):  
Chemical Evolution ◽  
Galactic Disk ◽  
Sodium Concentration ◽  
Mean Value ◽  
Heavy Elements ◽  
Solar Neighbourhood ◽  
Chemical Gradient ◽  
The Galaxy ◽  
The Mean ◽  
Image Position

An analysis of the kinematical and photometric properties of about 600dF stars and 600 gG-gK stars permits the estimation of the radial chemical gradient in the Galaxy. The mean value in the solar neighbourhood obtained for all of these stars is: The values of [Fe/H] used for this estimation are deduced for the dF stars using uvby β photometric measurements and for the gG-gK stars from a list published by Hansen and Kjaergaard. An estimate of the chemical gradient using UBV photometry of dG stars in the solar neighbourhood gives a similar value. For all the samples studied (dF, dG or giants) the order of magnitude for the gradient is the same. However, for the youngest stars in these samples the metallicity gradient could be larger: Such a value may be affected by dynamical perturbations of the galactic disk.The values published by Hansen and Kjaergaard for the sodium concentration in giant star atmospheres also indicate a radial galactic gradient of the same order.If only the dF stars which are sufficiently evolved to allow an age estimate are considered, then a very distinct correlation is found between age and metallicity: An important fraction of the heavy elements actually present in the solar neighbourhood seems to have synthetized during the life of the galactic disk.The two derivatives and are not independent, but are connected by the chemical evolution of the galactic disk. Some elementary deductions show the coherency of these two estimates.The intrinsic dispersion of metallicities, at a given age and birthplace, is somewhat lower than the admitted values. It has not been possible to find any significant variation with age of this quantity from the present observational material. The simultaneous variation of σ2w and [Fe/H] as function of age is evidence for a z stratification in the mean abundance of the heavy elements. The ratio between the mean metallicity in the plane and at z = 500 pc is estimated to be about a factor of two.Finally it is shown that the interpretation of the kinematical diagrams for different groups of given metallicity is ambiguous. A relation as e vs [Fe/H] depends not only on the chemical and kinematical history of the Galaxy but is also strongly dependent on the observational errors of [Fe/H] and on criteria used to define the sample.A paper containing the above results has been submitted for publication in Astronomy and Astrophysics.

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