scholarly journals Chemical evolution of the Galaxy disk in connection with large-scale winds

2008 ◽  
Vol 4 (S254) ◽  
pp. 393-398
Author(s):  
Takuji Tsujimoto ◽  
Joss Bland-Hawthorn ◽  
Kenneth C. Freeman
Keyword(s):  
Chemical Evolution ◽  
Large Scale ◽  
Solar Neighborhood ◽  
Elemental Abundance ◽  
Abundance Gradient ◽  
Chemical Enrichment ◽  
Outer Disk ◽  
The Galaxy ◽  
Galaxy Disk ◽  
Set Up

AbstractComparison of elemental abundance features between old and young thin disk stars may reveal the action of ravaging winds from the Galactic bulge, which once enriched the whole disk, and set up the steep abundance gradient in the inner disk (RGC ≲ 10–;12 kpc) and simultaneously the metallicity floor ([Fe/H]~ −0.5) in the outer disk. After the end of a crucial influence by winds, chemical enrichment through accretion of a metal-poor material from the halo onto the disk gradually reduced the metallicity of the inner region, whereas an increase in the metallicity proceeded beyond a solar circle. This results in a flattening of abundance gradient in the inner disk, and our chemical evolution models confirm this mechanism for a flattening, which is in good agreement with the observations. Our scenario also naturally explains an observed break in the metallicity floor of the outer disk by young stars since the limit of self-enrichment in the outer disk is supposed to be [Fe/H]≲ −1 and inevitably incurs a direct influence of the dilution by a low-metal infall whose metallicity is [Fe/H]~ −1. Accordingly, we propose that the enrichment by large-scale winds is a crucial factor for chemical evolution of the disk, and claim to reconsider the models thus far for the disk including the solar neighborhood, in which the metallicity is predicted to monotonously increase with time. Furthermore, we anticipate that a flattening of abundance gradient together with a metal-rich floor in the outer disk are the hallmark of disk galaxies with significant central bulges.

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 Measuring Outer Disk Warps with Optical Spectroscopy

2008 ◽  
Vol 4 (S254) ◽  
pp. 283-288
Author(s):  
Daniel Christlein ◽  
Joss Bland-Hawthorn
Keyword(s):  
Star Formation ◽  
Optical Spectroscopy ◽  
Column Density ◽  
Rotational Velocity ◽  
Chemical Abundances ◽  
Circular Velocity ◽  
Outer Disk ◽  
The Galaxy ◽  
Galaxy Disk ◽  
Interesting Alternative

AbstractWarps in the outer gaseous disks of galaxies are a ubiquitous phenomenon, but it is still unclear what generates them. One theory is that warps are generated internally through spontaneous bending instabilities. Other theories suggest that they result from the interaction of the outer disk with accreting extragalactic material. In this case, we expect to find cases where the circular velocity of the warp gas is poorly correlated with the rotational velocity of the galaxy disk at the same radius. Optical spectroscopy presents itself as an interesting alternative to 21-cm observations for testing this prediction, because (i) separating the kinematics of the warp from those of the disk requires a spatial resolution that is higher than what is achieved at 21 cm at low HI column density; (ii) optical spectroscopy also provides important information on star formation rates, gas excitation, and chemical abundances, which provide clues to the origin of the gas in warps. We present here preliminary results of a study of the kinematics of gas in the outer-disk warps of seven edge-on galaxies, using multi-hour VLT/FORS2 spectroscopy.

scholarly journals Primeval oxygen overabundance and type I-1/2 supernovae

1984 ◽  
Vol 105 ◽  
pp. 577-578
Author(s):  
F. Matteucci ◽  
A. Tornambé
Keyword(s):  
Chemical Evolution ◽  
Stellar Population ◽  
Type I ◽  
Chemical Enrichment ◽  
The Galaxy

Models of chemical evolution of the Galaxy have been computed by taking into account the different roles played by TypeI-1/2 (single stars suffering degenerate C-ignition) and Typell supernovae in the chemical enrichment. The overabundance of oxygen observed in the Halo stellar population has been well reproduced.

scholarly journals Galactic Chemical Evolution in the Context of the Recently Revealed SNe Ia Delay Time Distribution

2011 ◽  
Vol 7 (S281) ◽  
pp. 251-252
Author(s):  
Takuji Tsujimoto
Keyword(s):  
Chemical Evolution ◽  
Delay Time ◽  
Time Distribution ◽  
Chemical Properties ◽  
Thin Disk ◽  
Chemical Enrichment ◽  
Precise Knowledge ◽  
The Galaxy ◽  
Type Ia ◽  
Ia Supernovae

AbstractThe Galaxy is composed of four distinct structures, i.e., halo, bulge, and thick and thin disks, that are formed and evolved on different timescales; thus accordingly the speeds of chemical enrichment are different from one another, which is imprinted in individual stellar abundances. To decipher them, precise knowledge of the timing of the release of nucleosynthesis materials from various production sites is critical. The delay time distribution (DTD) of Type Ia supernovae (SNe Ia), recently revealed by the SNe Ia surveys of external galaxies, is incorporated into the models of chemical evolution for each structure. Here we report that the observed chemical properties for the thin and thick disks are compatible with a new SNe Ia DTD, and suggests a close chemical connection between the two in the way that the thin disk is formed from gas left after thick disk formation. This nicely explains the lack of thin disk stars with [Fe/H] ≲ −0.8. In this new context, a top-heavy IMF for the bulge is firmly confirmed. Finally we discuss the possibility of some modification of the DTD that might be considered for the halo case.

scholarly journals Supernova Yields for Chemical Evolution Modeling

2013 ◽  
Vol 9 (S298) ◽  
pp. 154-166
Author(s):  
Ken'ichi Nomoto ◽  
Tomoharu Suzuki
Keyword(s):  
Chemical Evolution ◽  
Massive Stars ◽  
Elemental Abundance ◽  
Solar Abundance ◽  
Abundance Pattern ◽  
Chemical Enrichment ◽  
Abundance Patterns ◽  
Yield Table ◽  
Supernova Explosions ◽  
Evolution Modeling

AbstractWe review the recent results of the nucleosynthesis yields of massive stars. We examine how those yields are affected by some hydrodynamical effects during the supernova explosions, namely, explosion energies from those of hypernovae to faint supernovae, mixing and fallback of processed materials, asphericity, etc. Those parameters in the supernova nucleosynthesis models are constrained from observational data of supernovae and metal-poor stars. The elemental abundance patterns observed in extremely metal-poor stars show some peculiarities relative to the solar abundance pattern, which suggests the important contributions of hypernovae and faint supernovae in the early chemical enrichment of galaxies. These constraints on supernova nucleosynthesis are taken into account in the latest yield table for chemical evolution modeling.

scholarly journals The Galactic Thick Disk: An Observational Perspective

2009 ◽  
Vol 5 (S265) ◽  
pp. 289-299
Author(s):  
Bacham E. Reddy
Keyword(s):  
Galaxy Formation ◽  
Chemical Properties ◽  
Thick Disk ◽  
Elemental Abundance ◽  
Distinct Component ◽  
Chemical Enrichment ◽  
Abundance Patterns ◽  
The Galaxy ◽  
Star Formation Histories ◽  
And Chemical Properties

AbstractIn this review, we present a brief description of observational efforts to understand the Galactic thick disk and its relation to the other Galactic components. This review primarily focused on elemental abundance patterns of the thick disk population to understand the process or processes that were responsible for its existence and evolution. Kinematic and chemical properties of disk stars establish that the thick disk is a distinct component in the Milky Way, and its chemical enrichment and star formation histories hold clues to the bigger picture of understanding the Galaxy formation.

scholarly journals Impact of Hypernova νp-process Nucleosynthesis on the Galactic Chemical Evolution of Mo and Ru

2022 ◽  
Vol 924 (1) ◽  
pp. 29
Author(s):  
Hirokazu Sasaki ◽  
Yuta Yamazaki ◽  
Toshitaka Kajino ◽  
Motohiko Kusakabe ◽  
Takehito Hayakawa ◽  
...  
Keyword(s):  
Theoretical Prediction ◽  
Observational Data ◽  
Chemical Evolution ◽  
Elemental Abundance ◽  
Core Collapse ◽  
Galactic Chemical Evolution ◽  
Main Contributor ◽  
Elemental Abundances ◽  
The Galaxy ◽  
Low Metallicity

Abstract We calculate the Galactic Chemical Evolution of Mo and Ru by taking into account the contribution from ν p-process nucleosynthesis. We estimate yields of p-nuclei such as 92,94Mo and 96,98Ru through the ν p-process in various supernova progenitors based upon recent models. In particular, the ν p-process in energetic hypernovae produces a large amount of p-nuclei compared to the yield in ordinary core-collapse SNe. Because of this, the abundances of 92,94Mo and 96,98Ru in the Galaxy are significantly enhanced at [Fe/H] = 0 by the ν p-process. We find that the ν p-process in hypernovae is the main contributor to the elemental abundance of 92Mo at low metallicity [Fe/H] < −2. Our theoretical prediction of the elemental abundances in metal-poor stars becomes more consistent with observational data when the ν p-process in hypernovae is taken into account.

scholarly journals Two distinct halo populations in the solar neighborhood: evidence from stellar abundance of beryllium

2013 ◽  
Vol 9 (S298) ◽  
pp. 83-85
Author(s):  
Kefeng Tan ◽  
Gang Zhao
Keyword(s):  
Star Formation ◽  
Galactic Halo ◽  
Formation Rate ◽  
Solar Neighborhood ◽  
Elemental Abundance ◽  
Star Formation History ◽  
Dwarf Stars ◽  
Formation History ◽  
The Galaxy ◽  
History Of

AbstractIt is now generally believed that the Galaxy was formed through hierarchical merging, which means that different components of the Galaxy may have experienced different chemical evolution histories. Since alpha elements are mainly produced by core collapse supernovae, they are closely associated with the star formation history of the Galaxy. In this regard, Galactic components with different alpha elemental abundance patterns may show different behaviors in beryllium abundances since the production of beryllium is correlated with the cosmic rays and thus the supernovae. A recent study by Nissen & Schuster (2010) has revealed the existence of two distinct halo populations in the solar neighborhood based on the alpha elemental abundances and kinematics of 94 dwarf stars. We determined beryllium abundances for some of these stars and find systematic differences in beryllium abundances between these two halo populations. Our results consolidate the conclusion of two distinct halo populations in the solar neighborhood. Our results also show that beryllium abundance is a very good indicator of star formation rate, and could be used to trace the substructures of the Galactic halo.

Final Remarks: Connections between Chemical and Dynamical Evolution

1977 ◽  
Vol 45 ◽  
pp. 309-319
Author(s):  
Beatrice M. Tinsley
Keyword(s):  
Interstellar Medium ◽  
Chemical Evolution ◽  
Dynamical Evolution ◽  
Theoretical Background ◽  
Dynamical Processes ◽  
Chemical Enrichment ◽  
The Galaxy ◽  
History Of

Dynamical processes strongly affect the chemical enrichment of gas in galaxies, so abundances in stars and the Interstellar medium can be used as probes of the dynamical history of the Galaxy. By way of tying together some diverse points, rather than summarizing the conference, I shall discuss some examples of connections between chemical and dynamical evolution. The first section of this paper mentions some of the well-known ways in which dynamical processes can affect chemical evolution, in order to outline a theoretical background to the use of abundances as clues to dynamics.

scholarly journals Chemical composition of planet building blocks as predicted by stellar population synthesis

2019 ◽  
Vol 622 ◽  
pp. A49 ◽  
Author(s):  
N. Cabral ◽  
N. Lagarde ◽  
C. Reylé ◽  
A. Guilbert-Lepoutre ◽  
A. C. Robin
Keyword(s):  
Large Scale ◽  
Stellar Populations ◽  
Building Blocks ◽  
Solar Neighborhood ◽  
Atmospheric Composition ◽  
Chemical Abundance ◽  
Element Abundances ◽  
The Galaxy ◽  
Mass Fractions ◽  
Statistical Trends

Context. Future space missions (TESS, CHEOPS, PLATO, and the JWST) will considerably improve our understanding of the formation and history of planetary systems by providing accurate constraints on planetary radius, mass, and atmospheric composition. Currently, observations show that the presence of planetary companions is closely linked to the metallicity and the chemical abundances of the host stars. Aims. We aim to build an integrated tool for predicting the planet building blocks (PBBs) composition as a function of the stellar populations to interpret ongoing and future large surveys. The different stellar populations we observe in our Galaxy are characterized by different metallicities and α-element abundances. We here investigate the trends of the expected PBBs composition with the chemical abundance of the host star in different parts of the Galaxy. Methods. We synthesized stellar populations with the Besançon galaxy model, which includes stellar evolutionary tracks that are computed with the stellar evolution code STAREVOL. We integrated a previously published simple stoichiometric model into this code to determine the expected composition of the PBBs. Results. We determine the expected PBB composition around FGK stars for the four galactic populations (thin and thick disks, halo, and bulge) within the Milky Way. Our solar neighborhood simulations are in good agreement with the recent results obtained with the HARPS survey for firon, fw, and the heavy element mass fraction fZ. We present evidence of a clear dependence of firon and fw on the initial alpha abundances [α/Fe] of the host star. We find that the different initial [α/Fe] distributions in the different galactic populations lead to a bimodal distribution of PBB composition. Our simulations show an iron valley that separates PBBs with high and low iron mass fractions and a water valley that separates PBBs with high and low water mass fractions. Conclusions. We linked host star abundances and expected PBB composition in an integrated model of the Galaxy. The trends we derive are an important step for statistical analyses of expected planet properties. In particular, internal structure models may use these results to derive statistical trends of rocky planet properties, constrain habitability, and prepare an interpretation of ongoing and future large-scale surveys of exoplanets.

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