scholarly journals Multiple stellar populations: From old Milky Way globulars to young star clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 261-266
Author(s):  
Anna F. Marino
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Open Cluster ◽  
Chemical Properties ◽  
Stellar Populations ◽  
Large Magellanic Cloud ◽  
Young Star ◽  
Type I ◽  
Rotation Rates ◽  
Young Star Clusters

AbstractI present the latest results from our group about the multiple stellar populations in the old Milky Way globular clusters (GCs) and in the young systems both in the Magellanic Clouds and in the Milky Way. For the ancient GCs in our Galaxy I summarize the chemical properties of the stellar populations as observed on the chromosome map. Both Type I and Type II GCs are discussed. For the youngest clusters I will briefly report our latest spectroscopic analysis on the Large Magellanic Cloud cluster NGC 1818 and the Galactic open cluster M 11, which supports the co-existence of stellar populations with different rotation rates.

HR Diagrams of Galaxies: Ages and Stages of Evolution

1978 ◽  
Vol 80 ◽  
pp. 247-257
Author(s):  
Beatrice M. Tinsley
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Stellar Populations ◽  
Young Star ◽  
Red Giants ◽  
Type I ◽  
Type Ii ◽  
Hubble Sequence ◽  
The Galaxy ◽  
Bright Blue

Baade (1944) based his concept of stellar populations in galaxies on the HR diagrams that he inferred from the magnitude at which their brightest stars could be resolved. His type I population had bright blue supergiants like those in the disk of the Milky Way, while the brightest stars in type II were the red giants found in globular clusters. He postulated that the Hubble sequence of galaxy types from irregulars to ellipticals contained increasing proportions of Population II relative to Population I, and that similar differences characterized nuclear bulges of spirals relative to their disks. A very important revision of this picture came with the discovery by Morgan and Mayall (1957; Morgan, 1956, 1959) that the integrated blue light of the nuclear bulges of M31 and the Galaxy is dominated by strong-lined CN giants, not by the weak-lined type found in globular clusters. On the basis of integrated spectra of galaxies, Morgan developed a revised population scheme, in which the extreme types are a young-star rich population, like Baade's extreme Population I, and a young-star deficient population, analogous to Population II but generally metal-rich. Different proportions of these two types are still thought to represent the main differences among stellar populations in different regions of galaxies.

scholarly journals Young star clusters in the LMC

1991 ◽  
Vol 148 ◽  
pp. 177-181
Author(s):  
K. C. Freeman ◽  
R.A.W. Elson
Keyword(s):  
Globular Clusters ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Large Magellanic Cloud ◽  
Young Star ◽  
Magellanic Cloud ◽  
Initial Mass ◽  
Young Star Clusters ◽  
Mass Functions

We discuss the integrated colours, kinematics, formation, dynamical evolution and initial mass functions of the young globular star clusters in the Large Magellanic Cloud (LMC). Because these clusters are so young, they offer us insights, unobtainable from the old globular clusters in our Galaxy, into the formation and early dynamical evolution of globular clusters.

scholarly journals Chemical Abundances of Seven Outer Halo M31 Globular Clusters from the Pan-Andromeda Archaeological Survey

2016 ◽  
Vol 11 (S321) ◽  
pp. 10-12
Author(s):  
Charli M. Sakari
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Large Magellanic Cloud ◽  
Archaeological Survey ◽  
Chemical Abundances ◽  
Light Spectra ◽  
Sigma Level ◽  
Stellar Streams ◽  
Detailed Chemical

AbstractObservations of stellar streams in M31’s outer halo suggest that M31 is actively accreting several dwarf galaxies and their globular clusters (GCs). Detailed abundances can chemically link clusters to their birth environments, establishing whether or not a GC has been accreted from a satellite dwarf galaxy. This talk presents the detailed chemical abundances of seven M31 outer halo GCs (with projected distances from M31 greater than 30 kpc), as derived from high-resolution integrated-light spectra taken with the Hobby Eberly Telescope. Five of these clusters were recently discovered in the Pan-Andromeda Archaeological Survey (PAndAS)—this talk presents the first determinations of integrated Fe, Na, Mg, Ca, Ti, Ni, Ba, and Eu abundances for these clusters. Four of the target clusters (PA06, PA53, PA54, and PA56) are metal-poor ([Fe/H] < -1.5), α-enhanced (though they are possibly less alpha-enhanced than Milky Way stars at the 1 sigma level), and show signs of star-to-star Na and Mg variations. The other three GCs (H10, H23, and PA17) are more metal-rich, with metallicities ranging from [Fe/H] = -1.4 to -0.9. While H23 is chemically similar to Milky Way field stars, Milky Way GCs, and other M31 clusters, H10 and PA17 have moderately-low [Ca/Fe], compared to Milky Way field stars and clusters. Additionally, PA17’s high [Mg/Ca] and [Ba/Eu] ratios are distinct from Milky Way stars, and are in better agreement with the stars and clusters in the Large Magellanic Cloud (LMC). None of the clusters studied here can be conclusively linked to any of the identified streams from PAndAS; however, based on their locations, kinematics, metallicities, and detailed abundances, the most metal-rich PAndAS clusters H23 and PA17 may be associated with the progenitor of the Giant Stellar Stream, H10 may be associated with the SW Cloud, and PA53 and PA56 may be associated with the Eastern Cloud.

scholarly journals Globular clusters and the evolution of their multiple stellar populations

2015 ◽  
Vol 12 (S316) ◽  
pp. 328-333
Author(s):  
W. Chantereau ◽  
C. Charbonnel ◽  
G. Meynet
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Chemical Properties ◽  
Stellar Populations ◽  
Chemical Compositions ◽  
Low Mass Stars ◽  
Sequence Band ◽  
Low Mass ◽  
Chemical Distribution ◽  
Host Stars

AbstractOur knowledge of the formation and early evolution of globular clusters (GCs) has been totally shaken with the discovery of the peculiar chemical properties of their long-lived host stars. Therefore, the interpretation of the observed Colour Magnitude Diagrams (CMD) and of the properties of the GC stellar populations requires the use of new stellar models computed with relevant chemical compositions. In this paper we use the grid of evolution models for low-mass stars computed by Chantereau et al. (2015) with the initial compositions of second-generation stars as predicted by the fast rotating massive stars scenario to build synthesis models of GCs. We discuss the implications of the assumed initial chemical distribution on 13 Gyr isochrones. We build population synthesis models to predict the fraction of stars born with various helium abundances in present day globular clusters (assuming an age of 13 Gyr). With the current assumptions, 61 % of stars on the main sequence are predicted to be born with a helium abundance in mass fraction, Yini, smaller than 0.3 and only 11 % have a Yini larger than 0.4. Along the horizontal branch, the fraction of stars with Yini inferior to 0.3 is similar to that obtained along the main sequence band (63 %), while the fraction of very He-enriched stars is significantly decreased (only 3 % with Yini larger than 0.38).

Globular clusters and their link with stellar populations in the Milky Way

2019 ◽  
Vol 14 (S351) ◽  
pp. 19-23
Author(s):  
David Yong
Keyword(s):  
Chemical Evolution ◽  
Globular Clusters ◽  
Milky Way ◽  
Star Clusters ◽  
Stellar Populations ◽  
Chemical Compositions ◽  
Chemical Abundance ◽  
Chemical Enrichment ◽  
Similarities And Differences ◽  
Insight Into

AbstractObservations of stellar chemical compositions enable us to identify connections between globular clusters and stellar populations in the Milky Way. In particular, chemical abundance ratios provide detailed insight into the chemical enrichment histories of star clusters and the field populations. For some elements, there are striking differences between field and cluster stars which reflect different nucleosynthetic processes and/or chemical evolution. The goal of this talk was to provide an overview of similarities and differences in chemical compositions between globular clusters and the Milky Way as well as highlighting a few areas for further examination.

scholarly journals Population Models for Massive Globular Clusters

2012 ◽  
Vol 10 (H16) ◽  
pp. 247-248 ◽  
Author(s):  
Young-Wook Lee ◽  
Seok-Joo Joo ◽  
Sang-Il Han ◽  
Chongsam Na ◽  
Dongwook Lim ◽  
...  
Keyword(s):  
Parameter Space ◽  
Globular Clusters ◽  
Heavy Element ◽  
Milky Way ◽  
Population Modeling ◽  
Stellar Populations ◽  
Population Models ◽  
Horizontal Branch ◽  
Element Abundances ◽  
Hr Diagram

Increasing number of massive globular clusters (GCs) in the Milky Way are now turned out to host multiple stellar populations having different heavy element abundances enriched by supernovae. Recent observations have further shown that [CNO/Fe] is also enhanced in metal-rich subpopulations in most of these GCs, including ω Cen and M22 (Marino et al. 2011, 2012). In order to reflect this in our population modeling, we have expanded the parameter space of Y2 isochrones and horizontal-branch (HB) evolutionary tracks to include the cases of normal and enhanced nitrogen abundances ([N/Fe] = 0.0, 0.8, and 1.6). The observed variations in the total CNO content were reproduced by interpolating these nitrogen enhanced stellar models. Our test simulations with varying N and O abundances show that, once the total CNO sum ([CNO/Fe]) is held constant, both N and O have almost identical effects on the HR diagram (see Fig. 1).

scholarly journals Star Clusters and Stellar Populations of the M31 Disk as Viewed by HST

2002 ◽  
Vol 207 ◽  
pp. 149-151
Author(s):  
Benjamin F. Williams ◽  
Paul W. Hodge
Keyword(s):  
Star Clusters ◽  
Stellar Populations ◽  
Young Star ◽  
Young Stars ◽  
New Method ◽  
Data Archive ◽  
Stellar Photometry ◽  
Identification Method ◽  
Ob Associations ◽  
Young Star Clusters

We present a new method for finding associations of young stars in M31 using broadband WFPC2 data from the HST data archive. Applying our identification method to 13 WFPC2 fields, covering an area of ∼60 arcmin2, has revealed 80 new candidate young star clusters in these portions of the M31 disk. Most of these clusters are small (≳5 pc) young (∼10–200 Myr) star groups located within large OB associations. We have estimated the reddening values and the ages of each candidate individually by fitting isochrones to the stellar photometry. We provide a catalogue of the candidates including rough approximations of their reddenings and ages.

scholarly journals Revisiting nucleosynthesis in globular clusters

2017 ◽  
Vol 608 ◽  
pp. A28 ◽  
Author(s):  
N. Prantzos ◽  
C. Charbonnel ◽  
C. Iliadis
Keyword(s):  
Nuclear Reaction ◽  
Constant Temperature ◽  
Globular Clusters ◽  
Chemical Properties ◽  
Reaction Network ◽  
Stellar Populations ◽  
Reaction Rates ◽  
Temperature Range

Context. Motivated by recent reports concerning the observation of limited enrichment in He but excess K in stars of globular clusters, we revisit the H-burning conditions that lead to the chemical properties of multiple stellar populations in these systems. Aims. In particular, we are interested in correlations of He and K with other elements, such as O, Na, Al, Mg and Si, reported in stars of NGC 2808. Methods. We performed calculations of nucleosynthesis at constant temperature and density, exploring the temperature range of 25 to 200 × 106 K (25 to 200 MK), using a detailed nuclear reaction network and the most up-to-date nuclear reaction rates. Results. We find that Mg is the most sensitive “thermometer” of hydrostatic H-burning conditions, pointing to a temperature range of 70–80 MK for NGC 2808, while He is a lesser – but not negligible – constraint. Potassium can be produced at the levels reported for NGC 2808 at temperatures >180 MK and Si at T > 80 MK. However, in the former temperature range Al and Na are totally destroyed and no correlation can be obtained, in contrast to the reported observations. None of the putative polluter sources proposed so far seem to satisfy the ensemble of nucleosynthesis constraints.

scholarly journals Gaia Data Release 2

2018 ◽  
Vol 616 ◽  
pp. A12 ◽  
Author(s):  
◽  
A. Helmi ◽  
F. van Leeuwen ◽  
P. J. McMillan ◽  
D. Massari ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Proper Motions ◽  
Single Plane ◽  
Dwarf Spheroidal Galaxies ◽  
Orbital Parameters ◽  
Data Release ◽  
Using Data

Context. Aims. The goal of this paper is to demonstrate the outstanding quality of the second data release of the Gaia mission and its power for constraining many different aspects of the dynamics of the satellites of the Milky Way. We focus here on determining the proper motions of 75 Galactic globular clusters, nine dwarf spheroidal galaxies, one ultra-faint system, and the Large and Small Magellanic Clouds. Methods. Using data extracted from the Gaia archive, we derived the proper motions and parallaxes for these systems, as well as their uncertainties. We demonstrate that the errors, statistical and systematic, are relatively well understood. We integrated the orbits of these objects in three different Galactic potentials, and characterised their properties. We present the derived proper motions, space velocities, and characteristic orbital parameters in various tables to facilitate their use by the astronomical community. Results. Our limited and straightforward analyses have allowed us for example to (i) determine absolute and very precise proper motions for globular clusters; (ii) detect clear rotation signatures in the proper motions of at least five globular clusters; (iii) show that the satellites of the Milky Way are all on high-inclination orbits, but that they do not share a single plane of motion; (iv) derive a lower limit for the mass of the Milky Way of 9.1-2.6+6.2 × 1011 M⊙ based on the assumption that the Leo I dwarf spheroidal is bound; (v) derive a rotation curve for the Large Magellanic Cloud based solely on proper motions that is competitive with line-of-sight velocity curves, now using many orders of magnitude more sources; and (vi) unveil the dynamical effect of the bar on the motions of stars in the Large Magellanic Cloud. Conclusions. All these results highlight the incredible power of the Gaia astrometric mission, and in particular of its second data release.

scholarly journals Exploring the nature and synchronicity of early cluster formation in the Large Magellanic Cloud – IV. Evidence for multiple populations in Hodge 11 and NGC 2210

2019 ◽  
Vol 486 (4) ◽  
pp. 5581-5599 ◽  
Author(s):  
Christina K Gilligan ◽  
Brian Chaboyer ◽  
Jeffrey D Cummings ◽  
Dougal Mackey ◽  
Roger E Cohen ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Hubble Space Telescope ◽  
Cluster Formation ◽  
Stellar Populations ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Wide Field ◽  
Horizontal Branch ◽  
Advanced Camera For Surveys

Abstract We present a multiple population search in two old Large Magellanic Cloud (LMC) Globular clusters, Hodge 11 and NGC 2210. This work uses data from the Advanced Camera for Surveys and Wide Field Camera 3 on the Hubble Space Telescope from programme GO-14164 in Cycle 23. Both of these clusters exhibit a broadened main sequence with the second population representing (20 ± ∼5) per cent for NGC 2210 and (30 ± ∼5) per cent for Hodge 11. In both clusters, the smaller population is redder than the primary population, suggesting CNO variations. Hodge 11 also displays a bluer second population in the horizontal branch, which is evidence for helium enhancement. However, even though NGC 2210 shows similarities to Hodge 11 in the main sequence, there does not appear to be a second population on NGC 2210’s horizontal branch. This is the first photometric evidence that ancient LMC Globular clusters exhibit multiple stellar populations.

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