Abundances in the Galactic Disk

2002 ◽  
Vol 187 ◽  
pp. 91-96
Author(s):  
Bengt Edvardsson
Keyword(s):  
Empirical Study ◽  
Galactic Disk ◽  
Chemical Abundances ◽  
3 Dimensional ◽  
Individual Stars ◽  
Abundance Patterns ◽  
The Galaxy ◽  
History Of

The empirical study of the build-up of chemical abundances in the galactic disk is an important route to our understanding of the history of the Galaxy. It supplies a wealth of constraints to the models and simulations being done. There are, however, still many unanswered questions concerning the details of the abundance patterns, and many uncertainties and possibly inconsistencies in the data at hand. Ideally one would like to map the abundances of individual elements as a function of time and 3-dimensional position in the disk. The study of the ISM today and of the surfaces of individual stars as probes of the ISM from the time and position of their formation help us in this endeavour.

scholarly journals HERMES – An instrument of the future

2009 ◽  
Vol 5 (S262) ◽  
pp. 448-449 ◽  
Author(s):  
Elizabeth Wylie-de Boer ◽  
Kenneth Freeman
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Resolving Power ◽  
Individual Stars ◽  
Elemental Abundances ◽  
The Future ◽  
The Galaxy ◽  
History Of ◽  
High Resolution Spectrometer ◽  
Resolution Spectrometer

AbstractHERMES is a new, multi-object high resolution spectrometer for the 3.9m Anglo Australian Telescope, using the existing 2dF positioner. The primary goal of the HERMES survey is to unravel the history of the Galaxy from detailed elemental abundances for about 1.2 million individual stars. The HERMES chemical tagging survey concentrates on the 5000 to 8000 Å window at a resolving power of 30,000 in order to identify dissolved star formation aggregates and ascertain the importance of mergers throughout the history of the Galaxy.

The Nature of the Triangulum-Andromeda Stellar Structures

2018 ◽  
Vol 14 (S344) ◽  
pp. 122-124
Author(s):  
J. V. Sales Silva ◽  
H. Perottoni ◽  
K. Cunha ◽  
H. J. Rocha-Pinto ◽  
D. Souto ◽  
...  
Keyword(s):  
High Resolution ◽  
Kinematic Analysis ◽  
Dwarf Galaxies ◽  
Galactic Disk ◽  
Thin Disk ◽  
Atmospheric Parameters ◽  
Chemical Abundances ◽  
The Galaxy ◽  
Stellar Halo ◽  
Debris Cloud

AbstractThe outer stellar halo is home to a number of substructures that are remnants of former interactions of the Galaxy with its dwarf satellites. Triangulum-Andromeda (TriAnd) is one of these halo substructures, found as a debris cloud by Rocha-Pinto et al., (2004) using 2MASS M giants. Would be these structures related to dwarf galaxies or to the galactic disk? To uncover the nature of these stars we performed a high-resolution spectroscopic study (R = 40,000) along with a kinematic analysis using Gaia data. We determined the atmospheric parameters and chemical abundances of Ca and Mg for the 13 TriAnd candidate stars along with their respective orbits. Our results indicate that the TriAnd stars analyzed have a galactic nature but that these stars are not from the local thin disk.

scholarly journals Stellar Archaeology: Using Metal-Poor Stars to Test Theories of the Early Universe

2008 ◽  
Vol 4 (S255) ◽  
pp. 336-340
Author(s):  
Anna Frebel ◽  
Jarrett L. Johnson ◽  
Volker Bromm
Keyword(s):  
Fine Structure ◽  
Low Mass Stars ◽  
First Stars ◽  
Abundance Patterns ◽  
Cosmological Context ◽  
Different Types ◽  
The Galaxy ◽  
Structure Line ◽  
History Of ◽  
Low Mass

AbstractConstraints on the chemical yields of the first stars and supernova can be derived by examining the abundance patterns of different types of metal-poor stars. We show how metal-poor stars are employed to derive constraints of the formation of the first low-mass stars by testing a fine-structure line cooling theory. The concept of stellar archaeology, that stellar abundances truly reflect the chemical composition of the earliest times, is then addressed. The accretion history of a sample of metal-poor stars is examined in detail in a cosmological context, and found to have no impact on the observed abundances. Predictions are made for the lowest possible Fe and Mg abundances observable in the Galaxy, [Fe/H]min = −7.5 and [Mg/H]min = −5.5. The absence of stars below these values is so far consistent with a top-heavy IMF. These predictions are directly relevant for future surveys and the next generation of telescopes.

scholarly journals Kinematic age determinations of planetary nebula central stars

2011 ◽  
Vol 7 (S283) ◽  
pp. 486-487
Author(s):  
Thaise S. Rodrigues ◽  
Walter J. Maciel
Keyword(s):  
Galactic Disk ◽  
Age Determination ◽  
Large Mass ◽  
Chemical Abundance ◽  
Chemical Abundances ◽  
Stellar Ages ◽  
The Galaxy ◽  
Central Stars ◽  
Kinematic Properties ◽  
Mass Interval

AbstractCentral stars of planetary nebulae (CSPN) have a relatively large mass interval, so that it is expected that these stars also have different ages, typically above 1 Gyr. Apart from the properties of the CSPN themselves, the problem of age determination is also important in the context of the chemical evolution of the Galaxy, for instance in the understanding of the time variation of chemical abundance gradients. In this work, we estimated the ages of a sample of CSPN on the basis of some correlations between their kinematic properties and the expected ages. According to these correlations, the observed dispersions in the U, V, W velocities are uniquely defined by the stellar ages. The adopted correlations were derived from the recent Geneva-Copenhagen survey of galactic stars. Preliminary results suggest the most CSPN in the galactic disk have ages under 3 Gyr. These results are also compared with some recent age distributions based on independent correlations involving the nebular chemical abundances.

scholarly journals The Evolutionary History of the Milky Way

1996 ◽  
Vol 171 ◽  
pp. 3-10
Author(s):  
K.C. Freeman
Keyword(s):  
Evolutionary History ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Galactic Disk ◽  
Small Satellite ◽  
Galactic Bulge ◽  
The Galaxy ◽  
History Of ◽  
Satellite Galaxies

The accretion of small satellite galaxies appears to have been important in the formation of the metal-poor halo of the Galaxy. The disrupting Sgr dwarf galaxy and the recent discovery of a young, metal-poor component of the halo indicate that this is a continuing process. The evolution of the galactic disk, and some consequences of the bar-like nature of the galactic bulge are briefly discussed.

scholarly journals The abundance distribution of [α/Fe] in the Galactic disk stars

2013 ◽  
Vol 9 (S298) ◽  
pp. 419-420
Author(s):  
Ji Li ◽  
Ruijuan Fu
Keyword(s):  
Statistical Analysis ◽  
Star Formation ◽  
Chemical Evolution ◽  
Galactic Disk ◽  
Abundance Ratio ◽  
Thick Disk ◽  
Abundance Distribution ◽  
Dwarf Stars ◽  
The Galaxy ◽  
History Of

AbstractThe abundance ratio [α/Fe] is a useful tracer to probe the history of star formation and the chemical evolution of the Galaxy. We present a statistical analysis of [α/Fe] in 953 dwarf stars to investigate the distributions of [α/Fe] in the the thin- and thick-disk stars.

scholarly journals Chemical Abundances in Planetary Nebulae

1978 ◽  
Vol 76 ◽  
pp. 215-224 ◽  
Author(s):  
Manuel Peimbert
Keyword(s):  
Main Sequence ◽  
Galactic Disk ◽  
Type Ii ◽  
Orion Nebula ◽  
Main Sequence Stars ◽  
Chemical Abundances ◽  
Element Abundances ◽  
Oxygen Gradient ◽  
The Galaxy ◽  
Halo Population

PN can be divided into four types depending on their chemical composition. In order of decreasing heavy element abundances the types are: I) He and N rich, II) intermediate population, III) high velocity, and IV) halo population. The type II PN are overabundant in N and C relative to the Orion Nebula. Well defined gradients across the galactic disk of He, N and O are derived from type II PN; the oxygen gradient is similar to the metallicity gradient derived from GK giants and F main sequence stars. By comparing the O, Ne and S abundances of PN of types III and IV with the Fe abundances of stars of similar population it is found that the O, Ne and S enrichment in the Galaxy probably took place before the Fe enrichment.

scholarly journals A phylogenetic approach to chemical tagging

2018 ◽  
Vol 618 ◽  
pp. A65 ◽  
Author(s):  
Sergi Blanco-Cuaresma ◽  
Didier Fraix-Burnet
Keyword(s):  
Chemical Elements ◽  
Phylogenetic Analyses ◽  
Open Cluster ◽  
Open Clusters ◽  
Evolutionary Stage ◽  
The Sun ◽  
Chemical Abundances ◽  
Chemical Tagging ◽  
The Galaxy ◽  
History Of

Context. The chemical tagging technique is a promising approach to reconstructing the history of the Galaxy by only using stellar chemical abundances. Multiple studies have undertaken this analysis and they have raised several challenges. Aims. Using a sample of open cluster stars, we wish to address two issues: minimize chemical abundance differences whose origin is linked to the evolutionary stage of the stars and not their original composition and evaluate a phylogenetic approach to group stars based on their chemical composition. Methods. We derived differential chemical abundances for 207 stars, belonging to 34 open clusters, using the Sun as reference star (classical approach) and a dwarf plus a giant star from the open cluster M 67 as reference (new approach). These abundances were then used to perform two phylogenetic analyses: cladistics (maximum parsimony) and neighbor joining, together with a partitioning unsupervised classification analysis with k-means. The resulting groupings were finally confronted to the true open cluster memberships of the stars. Results. We successfully reconstruct most of the original open clusters when carefully selecting a subset of the abundances derived differentially with respect to M 67. We find a set of eight chemical elements that yield the best result and discuss the possible reasons for these elements to be good tracers of the history of the Galaxy. Conclusions. Our study shows that unraveling the history of the Galaxy by only using stellar chemical abundances is greatly improved provided that i) we perform a differential spectroscopic analysis with respect to an open cluster instead of the Sun, ii) select the chemical elements that are good tracers of the history of the Galaxy, and iii) use tools that are adapted to detect evolutionary tracks such as phylogenetic approaches.

scholarly journals Identification of Cool White Dwarfs in the Sloan Digital Sky Survey

2000 ◽  
Vol 176 ◽  
pp. 514-514 ◽  
Author(s):  
T. S. Metcalfe ◽  
A. Mukadam ◽  
D. E. Winget ◽  
X. Fan ◽  
M. A. Strauss ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Luminosity Function ◽  
Galactic Disk ◽  
Sloan Digital Sky Survey ◽  
Dwarf Stars ◽  
White Dwarf Stars ◽  
The Galaxy ◽  
History Of ◽  
Cool White Dwarfs

AbstractWe are searching for the coolest white dwarf stars in the galactic disk and halo. The Sloan survey, in due course, will identify an enormous number of new white dwarf stars which will better define the white dwarf luminosity function—an important tool for understanding the age and history of the stellar population of the galaxy. The broadband filter data obtained in the digital photometry phase of the survey will not permit identification of the most interesting of these, the coolest white dwarf stars. This is because the cool main sequence and subdwarf stars become indistinguishable from the white dwarfs in the various colorcolor diagrams. We have interference filters designed to separate out these classes of objects. We have obtained photometry of test fields to complement the Sloan data and identify the population of cool white dwarf stars. These data will ultimately resolve the controversies, based for the most part on small-number statistics, of the location of the turndown in the white dwarf luminosity function for the disk. If the halo is significantly older than the disk, we will find a second peak in the white dwarf luminosity function, at lower luminosities than the disk turndown. Our data will provide the first meaningful constraints on the location of the turndown in the halo white dwarf luminosity function.

scholarly journals A Flatter metallicity gradient in the Galactic disk: non-LTE abundance calculations of OB stars

2003 ◽  
Vol 212 ◽  
pp. 162-163 ◽  
Author(s):  
Simone Daflon ◽  
Katia Cunha
Keyword(s):  
Main Sequence ◽  
Galactic Disk ◽  
Main Sequence Stars ◽  
Chemical Abundances ◽  
Stellar Abundances ◽  
Ob Stars ◽  
The Galaxy ◽  
Aluminum Silicon

We present non-LTE abundances of carbon, nitrogen, oxygen, magnesium, aluminum, silicon and sulfur, derived for a sample of 70 O9-B2 main sequence stars of the Galactic disk and analyze the distribution of the chemical abundances in terms of radial gradients within 4.4-12.9 kpc from the center of the Galaxy. The derived gradients are flatter than those presented by the most recent studies about the radial gradients of stellar abundances.

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