scholarly journals Galactic Chemical Evolution

2003 ◽  
Vol 20 (4) ◽  
pp. 401-415 ◽  
Author(s):  
Brad K. Gibson ◽  
Yeshe Fenner ◽  
Agostino Renda ◽  
Daisuke Kawata ◽  
Hyun-chul Lee
Keyword(s):  
Boundary Condition ◽  
Galaxy Evolution ◽  
Chemical Evolution ◽  
Milky Way ◽  
State Of The Art ◽  
Galactic Chemical Evolution ◽  
Current State ◽  
Important Constraint

AbstractThe primary present-day observables upon which theories of galaxy evolution are based are a system’s morphology, dynamics, colour, and chemistry. Individually, each provides an important constraint to any given model; in concert, the four represent a fundamental (intractable) boundary condition for chemodynamical simulations. We review the current state-of-the-art semi-analytical and chemodynamical models for the Milky Way, emphasising the strengths and weaknesses of both approaches.

scholarly journals Chemical Evolution of R-process Elements in the Hierarchical Galaxy Formation

2015 ◽  
Vol 11 (S317) ◽  
pp. 318-319
Author(s):  
Yutaka Komiya ◽  
Toshikazu Shigeyama
Keyword(s):  
Neutron Star ◽  
Chemical Evolution ◽  
Galaxy Formation ◽  
Milky Way ◽  
Galactic Chemical Evolution ◽  
Halo Stars ◽  
R Process ◽  
Process Elements ◽  
Milky Way Halo

AbstractThe main astronomical source of r-process elements has not yet been identified. One plausible site is neutron star mergers (NSMs). From the perspective of Galactic chemical evolution, however, it has been pointed out that the NSM scenario is incompatible with observations. Recently, Tsujimoto & Shigeyama (2014) pointed out that NSM ejecta can spread into much larger volume than ejecta from a supernova. We re-examine the chemical evolution of r-process elements under the NSM scenario considering this difference in propagation of the ejecta. We find that the NSM scenario can be compatible with the observed abundances of the Milky Way halo stars.

scholarly journals The Milky Way Halo and the First Stars: New Frontiers in Galactic Archaeology

2009 ◽  
Vol 5 (H15) ◽  
pp. 184-184
Author(s):  
Timothy C. Beers ◽  
Jason Tumlinson ◽  
Brian O'Shea ◽  
Carolyn Peruta ◽  
Daniela Carollo
Keyword(s):  
Chemical Evolution ◽  
Milky Way ◽  
Galactic Chemical Evolution ◽  
Joint Effort ◽  
First Stars ◽  
Large Samples ◽  
New Models ◽  
First Galaxies ◽  
The Relationship ◽  
Milky Way Halo

AbstractWe discuss plans for a new joint effort between observers and theorists to understand the formation of the Milky Way halo back to the first epochs of chemical evolution. New models based on high-resolution N-body simulations coupled to simple models of Galactic chemical evolution show that surviving stars from the epoch of the first galaxies remain in the Milky Way today and should bear the nucleosynthetic imprint of the first stars. We investigate the key physical influences on the formation of stars in the first galaxies and how they appear today, including the relationship between cosmic reionization and surviving Milky Way stars. These models also provide a physically motivated picture of the formation of the Milky Ways “outer halo,” which has been identified from recent large samples of stars from SDSS. The next steps are to use these models to guide rigorous gas simulations of Milky Way formation, including its disk, and to gradually build up the fully detailed theoretical “Virtual Galaxy” that is demanded by the coming generation of massive Galactic stellar surveys.

scholarly journals The chemical evolution of the Galaxy

1985 ◽  
Vol 106 ◽  
pp. 587-596
Author(s):  
Bruce A. Twarog
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Chemical Evolution ◽  
Gas Dynamics ◽  
Common Point ◽  
Galactic Chemical Evolution ◽  
Stellar Nucleosynthesis ◽  
Double Edge ◽  
The Galaxy ◽  
Double Edge Sword

Over the last few years, our picture of the chemical evolution of the Galaxy has changed substantially. These changes are of interest because chemical evolution provides a common point of contact for most astrophysical processes of importance to galaxy evolution. By astrophysical processes we mean star formation, stellar nucleosynthesis, gas dynamics, etc. An understanding of galactic chemical evolution would allow us to place constraints on all of these topics simultaneously. This property, however, is a double-edge sword because, with so many variables involved, unique solutions to problems in chemical evolution are almost impossible.

scholarly journals Galactic evolution of D, 3He and 4He

2009 ◽  
Vol 5 (S268) ◽  
pp. 431-440
Author(s):  
Donatella Romano
Keyword(s):  
Magnetic Fields ◽  
Chemical Evolution ◽  
Globular Clusters ◽  
Milky Way ◽  
Galactic Evolution ◽  
Galactic Chemical Evolution ◽  
Low Mass Stars ◽  
Local Abundance ◽  
The Galaxy ◽  
Low Mass

AbstractThe uncertainties which still plague our understanding of the evolution of the light nuclides D, 3He and 4He in the Galaxy are described. Measurements of the local abundance of deuterium range over a factor of 3. The observed dispersion can be reconciled with the predictions on deuterium evolution from standard Galactic chemical evolution models, if the true local abundance of deuterium proves to be high, but not too high, and lower observed values are due to depletion onto dust grains. The nearly constancy of the 3He abundance with both time and position within the Galaxy implies a negligible production of this element in stars, at variance with predictions from standard stellar models which, however, do agree with the (few) measurements of 3He in planetary nebulae. Thermohaline mixing, inhibited by magnetic fields in a small fraction of low-mass stars, could in principle explain the complexity of the overall scenario. However, complete grids of stellar yields taking this mechanism into account are not available for use in chemical evolution models yet. Much effort has been devoted to unravel the origin of the extreme helium-rich stars which seem to inhabit the most massive Galactic globular clusters. Yet, the issue of 4He evolution is far from being fully settled even in the disc of the Milky Way.

scholarly journals Dispersal of massive star products and consequences for galactic chemical evolution

2003 ◽  
Vol 212 ◽  
pp. 620-629
Author(s):  
M. S. Oey
Keyword(s):  
Chemical Evolution ◽  
Massive Star ◽  
Milky Way ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Products ◽  
Galactic Chemical Evolution ◽  
Mixing Processes ◽  
Nearby Galaxies ◽  
Metallicity Distribution

The processes that disperse the products of massive stars from their birth sites play a fundamental role in determining the observed abundances. I discuss parameterizations for element dispersal and their roles in chemical evolution, with an emphasis on understanding present-day dispersion and homogeneity in metallicity. Turbulence dominates mixing processes, with characteristic timescales of order 108 yr, implying significant dilution of metals into the ISM. This permits a rough estimate of the metallicity distribution function of enrichment events. Many systems, including the Milky Way and nearby galaxies, show metallicity dispersions that as yet appear consistent with pure inhomogeneous evolution. There are also systems like I Zw 18 that show strong homogenization, perhaps tied to small galaxy size, high star formation rate, and/or superwinds.

scholarly journals L-GALAXIES 2020: The formation and chemical evolution of stellar haloes in Milky Way Analogues and galaxy clusters

2021 ◽  
Author(s):  
Geoff G Murphy ◽  
Robert M Yates ◽  
Shazrene S Mohamed
Keyword(s):  
Galaxy Clusters ◽  
Galaxy Evolution ◽  
Chemical Evolution ◽  
Milky Way ◽  
Good Correspondence ◽  
Cluster Galaxy ◽  
Radial Profiles ◽  
Stellar Halo ◽  
Stellar Masses ◽  
Good Agreement

Abstract We present an analysis of the formation and chemical evolution of stellar haloes around (a) Milky Way Analogue (MWA) galaxies and (b) galaxy clusters in the L-Galaxies 2020 semi-analytic model of galaxy evolution. Observed stellar halo properties are better reproduced when assuming a gradual stripping model for the removal of cold gas and stars from satellites, compared to an instantaneous stripping model. The slope of the stellar mass – metallicity relation for MWA stellar haloes is in good agreement with that observed in the local Universe. This extends the good agreement between L-Galaxies 2020 and metallicity observations from the gas and stars inside galaxies to those outside. Halo stars contribute on average only ∼0.1 per cent of the total circumgalactic medium (CGM) enrichment by z = 0 in MWAs, ejecting predominantly carbon produced by AGB stars. Around a quarter of MWAs have a single ‘significant progenitor’ with a mean mass of ∼ 2.3 × 109M⊙, similar to that measured for Gaia Enceladus. For galaxy clusters, L-Galaxies 2020 shows good correspondence with observations of stellar halo mass fractions, but slightly over-predicts stellar masses. Assuming a Navarro-Frenk-White profile for the stellar halo mass distribution provides the best agreement. On average, the intracluster stellar component (ICS) is responsible for 5.4 per cent of the total intracluster medium (ICM) iron enrichment, exceeding the contribution from the brightest cluster galaxy (BCG) by z = 0. We find that considering gradual stripping of satellites and realistic radial profiles is crucial for accurately modelling stellar halo formation on all scales in semi-analytic models.

Behavioral Genetics: Concepts for Research and Practice in Language Development and Disorders

1995 ◽  
Vol 38 (5) ◽  
pp. 1126-1142 ◽  
Author(s):  
Jeffrey W. Gilger
Keyword(s):  
Language Development ◽  
Behavioral Genetics ◽  
State Of The Art ◽  
Genetic Research ◽  
Great Promise ◽  
Behavioral Genetic ◽  
Fine Grained ◽  
Future Goals ◽  
Current State ◽  
Research Designs

This paper is an introduction to behavioral genetics for researchers and practioners in language development and disorders. The specific aims are to illustrate some essential concepts and to show how behavioral genetic research can be applied to the language sciences. Past genetic research on language-related traits has tended to focus on simple etiology (i.e., the heritability or familiality of language skills). The current state of the art, however, suggests that great promise lies in addressing more complex questions through behavioral genetic paradigms. In terms of future goals it is suggested that: (a) more behavioral genetic work of all types should be done—including replications and expansions of preliminary studies already in print; (b) work should focus on fine-grained, theory-based phenotypes with research designs that can address complex questions in language development; and (c) work in this area should utilize a variety of samples and methods (e.g., twin and family samples, heritability and segregation analyses, linkage and association tests, etc.).

Schizophrenia Research: Current State of the Art

1976 ◽  
Vol 21 (7) ◽  
pp. 497-498
Author(s):  
STANLEY GRAND
Keyword(s):  
State Of The Art ◽  
Current State
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