scholarly journals An extremely metal-deficient globular cluster in the Andromeda Galaxy

Science ◽  
2020 ◽  
Vol 370 (6519) ◽  
pp. 970-973
Author(s):  
Søren S. Larsen ◽  
Aaron J. Romanowsky ◽  
Jean P. Brodie ◽  
Asher Wasserman
Keyword(s):  
Early Universe ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Chemical Elements ◽  
Heavy Elements ◽  
The Sun ◽  
Andromeda Galaxy ◽  
Iron Abundance

Globular clusters (GCs) are dense, gravitationally bound systems of thousands to millions of stars. They are preferentially associated with the oldest components of galaxies, so measurements of their composition can constrain the build-up of chemical elements in galaxies during the early Universe. We report a massive GC in the Andromeda Galaxy (M31), RBC EXT8, that is extremely depleted in heavy elements. Its iron abundance is about 1/800 that of the Sun and about one-third that of the most iron-poor GCs previously known. It is also strongly depleted in magnesium. These measurements challenge the notion of a metallicity floor for GCs and theoretical expectations that massive GCs could not have formed at such low metallicities.

scholarly journals Cluster Mass and Metallicity Distributions: Reconstructing the Events During Halo Formation

2002 ◽  
Vol 207 ◽  
pp. 545-554
Author(s):  
William E. Harris
Keyword(s):  
Star Formation ◽  
Mass Distribution ◽  
Early Universe ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Potential Wells ◽  
Cluster Mass ◽  
Galactic Potential ◽  
Initial Power ◽  
Lines Of Evidence

Globular clusters in most large galaxies are a mixture of metal-poor and metal-rich (bimodal), but the halo stars are almost entirely metal-rich. This and other lines of evidence argue that the metal-poor globular clusters formed within widely distributed 108 − 109M⊙ gas clouds (supergiant GMCs) during an early burst in which most of the gas was ejected or unused till later rounds of star formation.New simulations of the growth of pre-galactic potential wells in the early universe now indicate that the initial power-law form of the globular cluster mass distribution (dN/dM ∼ M-1.8) is a miniature replica of the mass distribution of the SGMCs themselves, which grow hierarchically in the CDM potential wells of large protogalaxies.

The relationship between globular cluster parameters and abundance variations

2019 ◽  
Vol 14 (S351) ◽  
pp. 333-336
Author(s):  
David M. Nataf
Keyword(s):  
Early Universe ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Meta Analysis ◽  
Stellar Mass ◽  
Prior Literature ◽  
Nitrogen Abundance ◽  
Using Data ◽  
Sodium Abundance ◽  
The Relationship

AbstractWe discuss a meta-analysis of the association of abundance variations in globular cluster stars with the present-day stellar mass and metallicity of globular clusters. Using data for 42 globular clusters that are well-sampled from either or both of prior literature studies and the APOGEE survey, we confirm prior findings that increasing aluminum abundance variations in globular clusters are positively correlated with increasing present-day stellar mass or decreasing metallicity. We also demonstrate that the ratio of aluminum abundance variations to either nitrogen abundance variations or sodium abundance variations is itself positively correlated with decreasing metallicity and increasing stellar mass of globular clusters. This suggests that there were at least two non-supernovae chemical polluters that were active in the early universe.

scholarly journals Isochrones for Hydrogen‐burning Globular Cluster Stars. III. From the Sun to the Globular Clusters

1997 ◽  
Vol 490 (1) ◽  
pp. 425-436 ◽  
Author(s):  
Oscar Straniero ◽  
Alessandro Chieffi ◽  
Marco Limongi
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
The Sun ◽  
Hydrogen Burning

scholarly journals The Earth's Gold: Where Did It Really Come From?

2018 ◽  
Author(s):  
Elizabeth P. Tito ◽  
Vadim I. Pavlov
Keyword(s):  
Solar System ◽  
Milky Way ◽  
Chemical Elements ◽  
Heavy Elements ◽  
Terrestrial Planets ◽  
The Sun ◽  
Early Solar System ◽  
Reaction Channels

Why is it that in the neighborhood of a calm ordinary star (the Sun) located at the quiet periphery of its galaxy (the Milky Way), non-native heavy elements are abundant in such concentrated form? Where did these elements really come from? Where did Earth's gold come from? Our analysis of the known data offers a fact-reconciling hypothesis: What if, in the early solar system, an explosive collision occurred -- of a traveling from afar giant-nuclear-drop-like object with a local massive dense object (perhaps a then-existent companion of the Sun) -- and the debris, through the multitude of reaction channels and nuclei transformations, was then responsible for (1) the enrichment of the solar system with the cocktail of all detected exogenous chemical elements, and (2) the eventual formation of the terrestrial planets that pre-collision did not exist, thus offering a possible explanation for their inner position and compositional differences within the predominantly hydrogen-helium rest of the solar system.

scholarly journals The Main Sequence of the Very Old Globular Cluster NGC 6397

1980 ◽  
Vol 85 ◽  
pp. 423-423
Author(s):  
Gonzalo Alcaino ◽  
William Liller
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Narrow Range ◽  
Age Determination ◽  
The Sun ◽  
Age Of The Universe ◽  
The Universe ◽  
Photographic Photometry ◽  
Collapse Phase

We present photographic photometry for 1135 stars in the globular cluster NGC 6397, which, at a distance of 2.4 kpc, is most likely the second nearest globular to the Sun. The Racine wedge with the CTIO Yale 1 m telescope (Δm=3. 60 mag), the CTIO 4 m telescope (Δm=6. 83 mag) and the ESO 3.6 m telescope (Δm=3. 87 mag) was used to extend the photoelectric calibration from V≃16.1 to V≃20.7. The main sequence turnoff at V=16.7 and B-V=0.52 with respectively Mv =4.30 and (B-V)o =0.36 yields (m-M)v=12.40 and E(B-V)=0.16. Using the models of Iben and Rood (1970) and the isochrones of Demarque and McClure (1977), we deduce the cluster's age to be 17 × 109 years. This makes this object the oldest of the nine globular clusters with age determination and gives a lower limit to the age of the universe, rendering Ho ≤ 57 km sec−1 Mpc−1 if qo ≥ 0 is assumed. The large age spread of 6 billion years between NGC 6397 and 47 Tuc (the youngest counterpart with age data) indicates both that the protogalaxy underwent a slow collapse phase and that the abundances in globular clusters are lower for the oldest. The fact that the galactocentric distances for these clusters have the narrow range of 6 <R < 13 kpc makes it highly important to secure age data for extremely metal poor globulars far out in the halo.

On the Color Excesses of Globular Clusters

1988 ◽  
Vol 126 ◽  
pp. 529-530
Author(s):  
V. Straižys ◽  
R. Janulis
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Galactic Center ◽  
Galactic Plane ◽  
The Other ◽  
The Sun ◽  
General Direction ◽  
Dust Layer ◽  
Color Indices ◽  
The Galaxy

The interstellar reddening of globular clusters of the Galaxy is still an important unresolved problem, especially for metal-rich objects that are found usually at low galactic latitudes in the general direction of the galactic center. Their color excesses are needed in order to correct their color-magnitude diagrams and to determine their intrinsic integrated color indices. For this we need some method which is not related to measures of the cluster stars. One such method is to use foreground field stars in the direction of the globular cluster to measure the interstellar reddening. Because most of the globular clusters lie outside the galactic plane, we need information about the reddening in all the layer of absorbing dust in different directions. This information can be obtained by investigating stars which are at different distances from the Sun up to the edge of the absorbing dust layer. On the other hand, these stars should be as close as possible to the position of the globular cluster to avoid possible variations in the interstellar reddening in the area of the cluster.

scholarly journals Faint CCD photometry in globular clusters. II. Comparison of theoretical isochrones with the globular clusters M4 and M15

1984 ◽  
Vol 105 ◽  
pp. 147-151
Author(s):  
Harvey B. Richer ◽  
G.G. Fahlman
Keyword(s):  
Early Universe ◽  
Stellar Evolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Formation Time ◽  
Chemical Inhomogeneity ◽  
Ccd Photometry ◽  
Testing Ground ◽  
Astronomical Research

Globular cluster work touches on virtually all branches of astronomical research. The age of the globular system (or any variations in age among individual clusters) has important cosmological implications as well as relating to the formation time of the halo of our galaxy. Star to star chemical inhomogeneity within a cluster may set important constraints on either mixing within the stars themselves or on the chemical inhomogeneity of the early universe. Metallicity variations among clusters may provide the clue to galaxy-wide enrichment processes, while the cluster color-magnitude diagrams themselves are a testing ground for virtually every facet of stellar evolution.

UBV Photometry of RR Lyrae Variables in the Globular Cluster M4

1979 ◽  
Vol 46 ◽  
pp. 347-354 ◽  
Author(s):  
Carla Cacciari
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Normal Metal ◽  
Red Giants ◽  
The Sun ◽  
Horizontal Branch ◽  
Dark Clouds ◽  
Rr Lyrae ◽  
Metal Abundance ◽  
Ubv Photometry

M4, one of the closest globular clusters to the Sun, presents some peculiar features that make it very interesting to study. The first C-M diagram, published by Greenstein (1939), showed a well populated blue-horizontal branch, a characteristic which usually, but not always, indicates low metal abundance (Hartwick 1968). Kinman (1959) found however that it contains strong lined red giants and classified it as type A, indicating normal metal abundance. More recent C-M diagrams (Moshkalev 1975, Alcaino 1975, Lee 1977, Lloyd Evans 1977) substantially confirmed both these characteristics.One of the major problems in the study of this cluster is the high and possibly non-uni form reddening, due to its location behind the Scorpius-Ophiuchus dark clouds.

scholarly journals High-resolution abundance analysis of four red giants in the globular cluster NGC 6558

2018 ◽  
Vol 619 ◽  
pp. A178 ◽  
Author(s):  
B. Barbuy ◽  
L. Muniz ◽  
S. Ortolani ◽  
H. Ernandes ◽  
B. Dias ◽  
...  
Keyword(s):  
High Resolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Abundance Ratio ◽  
Mean Value ◽  
Heavy Elements ◽  
Spectroscopic Parameter ◽  
Red Giants ◽  
Abundance Pattern ◽  
Element Abundances

Context. NGC 6558 is a bulge globular cluster with a blue horizontal branch (BHB), combined with a metallicity of [Fe/H] ≈ −1.0. It is similar to HP 1 and NGC 6522, which could be among the oldest objects in the Galaxy. Element abundances in these clusters could reveal the nature of the first supernovae. Aims. We aim to carry out detailed spectroscopic analysis for four red giants of NGC 6558, in order to derive the abundances of the light elements C, N, O, Na, Al, the α-elements Mg, Si, Ca, Ti, and the heavy elements Y, Ba, and Eu. Methods. High-resolution spectra of four stars with FLAMES-UVES at VLT UT2-Kueyen were analysed. Spectroscopic parameter-derivation was based on excitation and ionization equilibrium of Fe I and Fe II. Results. This analysis results in a metallicity of [Fe/H] = − 1.17 ± 0.10 for NGC 6558. We find the expected α-element enhancements in O and Mg with [O/Fe] = +0.40, [Mg/Fe] = +0.33, and low enhancements in Si and Ca. Ti has a moderate enhancement of [Ti/Fe] = +0.22. The r-element Eu appears very enhanced with a mean value of [Eu/Fe] = +0.63. The first peak s-elements Y and Sr are also enhanced, these results have however to be treated with caution, given the uncertainties in the continuum definition; the use of neutral species (Sr I, Y I), instead of the dominant ionized species is another source of uncertainty. Ba appears to have a solar abundance ratio relative to Fe. Conclusions. NGC 6558 shows an abundance pattern that could be typical of the oldest inner bulge globular clusters, together with the pattern in the similar clusters NGC 6522 and HP 1. They show low abundances of the odd-Z elements Na and Al, and of the explosive nucleosynthesis α-elements Si, Ca, and Ti. The hydrostatic burning α-elements O and Mg are normally enhanced as expected in old stars enriched with yields from core-collapse supernovae, and the iron-peak elements Mn, Cu, Zn show low abundances, which is expected for Mn and Cu, but not for Zn. Finally, the cluster trio NGC 6558, NGC 6522, and HP 1 have relatively high abundances of first-peak heavy elements, variable second-peak element Ba, and the r-element Eu is enhanced. The latter is particularly high in NGC 6558.

scholarly journals Chemical analysis of the Bulge Globular Cluster NGC 6553

2021 ◽  
Author(s):  
Carolina Montecinos ◽  
S Villanova ◽  
C Muñoz ◽  
C C Cortés
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Chemical Elements ◽  
Spectroscopic Studies ◽  
Chemical Abundances ◽  
Origin And Evolution ◽  
Horizontal Branch Stars ◽  
The Galaxy ◽  
Significant Spread ◽  
Good Agreement

Abstract Globular Clusters are among the oldest objects in the Galaxy, thus their researchers are key to understanding the processes of evolution and formation that the galaxy has experienced in early stages. Spectroscopic studies allow us to carry out detailed analyzes on the chemical composition of Globular Clusters. The aim of our research is to perform a detailed analysis of chemical abundances to a sample of stars of the Bulge Globular Cluster NGC 6553, in order to determine chemical patterns that allow us to appreciate the phenomenon of Multiple Population in one of the most metal-rich Globular Clusters in the Galaxy. This analysis is being carried out with data obtained by FLAMES/GIRAFFE spectrograph, VVV Survey and DR2 of Gaia Mission. We analyzed 20 Red Horizontal Branch Stars, being the first extensive spectroscopic abundance analysis for this cluster and measured 8 chemical elements (O, Na, Mg, Si, Ca, Ti, Cr and Ni), deriving a mean iron content of [Fe/H] = −0.10 ± 0.01 and a mean of [α/Fe] = 0.21 ± 0.02, considering Mg, Si, Ca and Ti (errors on the mean). We found a significant spread in the content of Na but a small or negligible in O. We did not find an intrinsic variation in the content of α and iron-peak elements, showing a good agreement with the trend of the Bulge field stars, suggesting a similar origin and evolution.

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