Structure and Evolution of the Milky Way Galaxy

AbstractThe combination of chemical abundance, kinematic, and age data for stars near the sun provides important information about the early evolution of the Galaxy. We review available data, with some new analysis, to show that the sum of all available information strongly suggests that the extreme population II subdwarf system formed during a period of rapid collapse of the proto-Galaxy. This subdwarf system now forms a flattened, pressure-supported distribution, with axial ratio ∼2:1. The thick disk formed subsequent to the subdwarf system. At least the metal-poor tail of the thick disk is comparable in age to the globular cluster system. The thick disk is probably kinematically discrete from the Galactic old disk, though the data remain inadequate for robust conclusions.

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The globular cluster system of the Auriga simulations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1380 ◽

2020 ◽

Vol 496 (1) ◽

pp. 638-648 ◽

Cited By ~ 1

Author(s):

Timo L R Halbesma ◽

Robert J J Grand ◽

Facundo A Gómez ◽

Federico Marinacci ◽

Rüdiger Pakmor ◽

...

Keyword(s):

Globular Cluster ◽

Milky Way ◽

Cluster Formation ◽

Solar Radius ◽

High Mass ◽

Formation Model ◽

The Galaxy ◽

High Mass Loss ◽

Globular Cluster System ◽

Varying Mass

ABSTRACT We investigate whether the galaxy and star formation model used for the Auriga simulations can produce a realistic globular cluster (GC) population. We compare statistics of GC candidate star particles in the Auriga haloes with catalogues of the Milky Way (MW) and Andromeda (M31) GC populations. We find that the Auriga simulations do produce sufficient stellar mass for GC candidates at radii and metallicities that are typical for the MW GC system (GCS). We also find varying mass ratios of the simulated GC candidates relative to the observed mass in the MW and M31 GCSs for different bins of galactocentric radius metallicity (rgal–[Fe/H]). Overall, the Auriga simulations produce GC candidates with higher metallicities than the MW and M31 GCS and they are found at larger radii than observed. The Auriga simulations would require bound cluster formation efficiencies higher than 10 per cent for the metal-poor GC candidates, and those within the Solar radius should experience negligible destruction rates to be consistent with observations. GC candidates in the outer halo, on the other hand, should either have low formation efficiencies, or experience high mass-loss for the Auriga simulations to produce a GCS that is consistent with that of the MW or M31. Finally, the scatter in the metallicity as well as in the radial distribution between different Auriga runs is considerably smaller than the differences between that of the MW and M31 GCSs. The Auriga model is unlikely to give rise to a GCS that can be consistent with both galaxies.

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An Overview of the Globular Cluster System of the Galaxy

Symposium - International Astronomical Union ◽

10.1017/s0074180900042376 ◽

1988 ◽

Vol 126 ◽

pp. 37-48

Author(s):

Robert Zinn

Keyword(s):

Globular Cluster ◽

Globular Clusters ◽

Milky Way ◽

Galactic Center ◽

Galactic Plane ◽

Cluster System ◽

Open Clusters ◽

The Galaxy ◽

Globular Cluster System ◽

Harlow Shapley

Harlow Shapley (1918) used the positions of globular clusters in space to determine the dimensions of our Galaxy. His conclusion that the Sun does not lie near the center of the Galaxy is widely recognized as one of the most important astronomical discoveries of this century. Nearly as important, but much less publicized, was his realization that, unlike stars, open clusters, HII regions and planetary nebulae, globular clusters are not concentrated near the plane of the Milky Way. His data showed that the globular clusters are distributed over very large distances from the galactic plane and the galactic center. Ever since this discovery that the Galaxy has a vast halo containing globular clusters, it has been clear that these clusters are key objects for probing the evolution of the Galaxy. Later work, which showed that globular clusters are very old and, on average, very metal poor, underscored their importance. In the spirit of this research, which started with Shapley's, this review discusses the characteristics of the globular cluster system that have the most bearing on the evolution of the Galaxy.

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Dynamics of Globular Cluster Systems

Symposium - International Astronomical Union ◽

10.1017/s007418090003326x ◽

1983 ◽

Vol 100 ◽

pp. 359-364

Author(s):

K. C. Freeman

Keyword(s):

Globular Cluster ◽

Globular Clusters ◽

Milky Way ◽

Cluster Formation ◽

Active Phase ◽

Chemical Abundance ◽

Cluster Systems ◽

Chemical Enrichment ◽

Wide Range ◽

The Galaxy

In the Milky Way, the globular clusters are all very old, and we are accustomed to think of them as the oldest objects in the Galaxy. The clusters cover a wide range of chemical abundance, from near solar down to about [Fe/H] ⋍ −2.3. However there are field stars with abundances significantly lower than −2.3 (eg Bond, 1980); this implies that the clusters formed during the active phase of chemical enrichment, with cluster formation beginning at a time when the enrichment processes were already well under way.

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Galactic orbits of stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900105340 ◽

1966 ◽

Vol 25 ◽

pp. 93-97

Author(s):

Richard Woolley

Keyword(s):

Globular Cluster ◽

Potential Field ◽

High Velocity ◽

Velocity Vector ◽

Variable Stars ◽

The Sun ◽

Proper Motions ◽

Rr Lyrae ◽

The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

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The Long View of Planetary Systems

10.1093/oso/9780198799894.003.0011 ◽

2018 ◽

Author(s):

Karel Schrijver

Keyword(s):

Solar System ◽

Milky Way ◽

Planetary Systems ◽

Giant Planets ◽

Milky Way Galaxy ◽

Population Statistics ◽

The Past ◽

General Terms ◽

The Galaxy ◽

The Universe

How many planetary systems formed before our’s did, and how many will form after? How old is the average exoplanet in the Galaxy? When did the earliest planets start forming? How different are the ages of terrestrial and giant planets? And, ultimately, what will the fate be of our Solar System, of the Milky Way Galaxy, and of the Universe around us? We cannot know the fate of individual exoplanets with great certainty, but based on population statistics this chapter sketches the past, present, and future of exoworlds and of our Earth in general terms.

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The Milky Way globular cluster system within the context of a closed box

Astrophysics and Space Science ◽

10.1007/s10509-020-03897-0 ◽

2020 ◽

Vol 365 (12) ◽

Author(s):

Graeme H. Smith

Keyword(s):

Globular Cluster ◽

Milky Way ◽

Cluster System ◽

Globular Cluster System

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A Statistical Estimation of the Occurrence of Extraterrestrial Intelligence in the Milky Way Galaxy

Galaxies ◽

10.3390/galaxies9010005 ◽

2021 ◽

Vol 9 (1) ◽

pp. 5

Author(s):

Xiang Cai ◽

Jonathan H. Jiang ◽

Kristen A. Fahy ◽

Yuk L. Yung

Keyword(s):

Statistical Estimation ◽

Milky Way ◽

Galactic Center ◽

Model Simulation ◽

Temporal Variations ◽

Extraterrestrial Intelligence ◽

Milky Way Galaxy ◽

The Galaxy ◽

Peak Location ◽

Intelligent Life

In the field of astrobiology, the precise location, prevalence, and age of potential extraterrestrial intelligence (ETI) have not been explicitly explored. Here, we address these inquiries using an empirical galactic simulation model to analyze the spatial–temporal variations and the prevalence of potential ETI within the Galaxy. This model estimates the occurrence of ETI, providing guidance on where to look for intelligent life in the Search for ETI (SETI) with a set of criteria, including well-established astrophysical properties of the Milky Way. Further, typically overlooked factors such as the process of abiogenesis, different evolutionary timescales, and potential self-annihilation are incorporated to explore the growth propensity of ETI. We examine three major parameters: (1) the likelihood rate of abiogenesis (λA); (2) evolutionary timescales (Tevo); and (3) probability of self-annihilation of complex life (Pann). We found Pann to be the most influential parameter determining the quantity and age of galactic intelligent life. Our model simulation also identified a peak location for ETI at an annular region approximately 4 kpc from the galactic center around 8 billion years (Gyrs), with complex life decreasing temporally and spatially from the peak point, asserting a high likelihood of intelligent life in the galactic inner disk. The simulated age distributions also suggest that most of the intelligent life in our galaxy are young, thus making observation or detection difficult.

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Kinematical & Chemical Characteristics of the Thin and Thick Disks

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308027579 ◽

2008 ◽

Vol 4 (S254) ◽

pp. 179-190 ◽

Cited By ~ 2

Author(s):

Rosemary F. G. Wyse

Keyword(s):

Dark Matter ◽

Cold Dark Matter ◽

Milky Way ◽

Observational Evidence ◽

Chemical Characteristics ◽

Chemical Abundance ◽

The Galaxy ◽

History Of ◽

Thin And Thick Disks ◽

Thick Disks

AbstractI discuss how the chemical abundance distributions, kinematics and age distributions of stars in the thin and thick disks of the Galaxy can be used to decipher the merger history of the Milky Way, a typical large galaxy. The observational evidence points to a rather quiescent past merging history, unusual in the context of the ‘consensus’ cold-dark-matter cosmology favoured from observations of structure on scales larger than individual galaxies.

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