scholarly journals Nucleosynthesis in the Stellar Systems ω Centauri and M22

2011 ◽  
Vol 28 (1) ◽  
pp. 28-37 ◽  
Author(s):  
G. S. Da Costa ◽  
A. F. Marino
Keyword(s):  
Globular Cluster ◽  
Total Mass ◽  
Large Range ◽  
Stellar System ◽  
Stellar Systems ◽  
Elemental Abundances ◽  
Two Systems ◽  
Red Giant ◽  
Using Data ◽  
Giant Branch Stars

AbstractThe stellar system ω Centauri (ω Cen) is well known for the large range in elemental abundances among its member stars. Recent work has indicated that the globular cluster M22 (NGC 6656) also possesses an internal abundance range, albeit substantially smallerthan that in ω Cen. Here we compare, as a function of [Fe/H], element-to-iron ratios in the two systems for a number of different elements using data from abundance analyses of red giant branch stars. It appears that the nucleosynthetic enrichment processes were very similar in these two systems despite the substantial difference in total mass.

scholarly journals Lithium abundance in lower red giant branch stars of Omega Centauri

2018 ◽  
Vol 618 ◽  
pp. A134 ◽  
Author(s):  
A. Mucciarelli ◽  
M. Salaris ◽  
L. Monaco ◽  
P. Bonifacio ◽  
X. Fu ◽  
...  
Keyword(s):  
High Resolution ◽  
Globular Clusters ◽  
Stellar System ◽  
The Other ◽  
Large Telescope ◽  
Lithium Abundance ◽  
Very Large Telescope ◽  
Red Giant ◽  
Giant Branch Stars ◽  
Branch Star

We present Li, Na, Al, and Fe abundances of 199 lower red giant branch star members of the stellar system Omega Centauri, using high-resolution spectra acquired with FLAMES at the Very Large Telescope. The A(Li) distribution is peaked at A(Li) ∼ 1 dex with a prominent tail towards lower values. The peak of the distribution well agrees with the lithium abundances measured in lower red giant branch stars in globular clusters and Galactic field stars. Stars with A(Li) ∼ 1 dex are found at metallicities lower than [Fe/H] ∼ –1.3 dex but they disappear at higher metallicities. On the other hand, Li-poor stars are found at all metallicities. The most metal-poor stars exhibit a clear Li–Na anti-correlation, where about 30% of the sample have A(Li) lower than ∼0.8 dex, while these stars represent a small fraction of normal globular clusters. Most of the stars with [Fe/H] > –1.6 dex are Li poor and Na rich. The Li depletion measured in these stars is not observed in globular clusters with similar metallicities and we demonstrate that it is not caused by the proposed helium enhancements and/or young ages. Hence, these stars formed from a gas already depleted in lithium. Finally, we note that Omega Centauri includes all the populations (Li-normal/Na-normal, Li-normal/Na-rich, and Li-poor/Na-rich stars) observed, to a lesser extent, in mono-metallic GCs.

scholarly journals Formation of globular clusters with multiple stellar populations from massive gas clumps in high-z gas-rich dwarf galaxies

2019 ◽  
Vol 622 ◽  
pp. A53 ◽  
Author(s):  
K. Bekki
Keyword(s):  
Mass Fraction ◽  
Total Mass ◽  
Globular Clusters ◽  
Dwarf Galaxies ◽  
Stellar System ◽  
Stellar Populations ◽  
Stellar Systems ◽  
Agb Stars ◽  
Time Step ◽  
Gas Accretion

Context. One of the currently favored scenarios for the formation of globular clusters (GCs) with multiple stellar populations is that an initial massive stellar system forms (“first generation”, FG), subsequently giving rise to gaseous ejecta which is converted into a second-generation (SG) of stars to form a GC. How such GCs with such FG and SG populations form and evolve, however, remains unclear. Aims. We therefore investigate, for the first time, the sequential formation processes of both FG and SG stars from star-forming massive gas clumps in gas-rich dwarf disk galaxies. Methods. We adopt a novel approach to resolve the two-stage formation of GCs in hydrodynamical simulations of dwarf galaxies. In the new simulations, new gas particles that are much less massive than their parent star particle are generated around each new star particle when the new star enters into the asymptotic giant branch (AGB) phase. Furthermore, much finer maximum time step width (~105 yr) and smaller softening length (~2 pc) are adopted for such AGB gas particles to properly resolve the ejection of gas from AGB stars and AGB feedback effects. Therefore, secondary star formation from AGB ejecta can be properly investigated in galaxy-scale simulations. Results. An FG stellar system can first form from a massive gas clump developing due to gravitational instability within its host gas-rich dwarf galaxy. Initially the FG stellar system is not a single massive cluster, but instead is composed of several irregular stellar clumps (or filaments) with a total mass larger than 106 M⊙. While the FG system is dynamically relaxing, gaseous ejecta from AGB stars can be gravitationally trapped by the FG system and subsequently converted into new stars to form a compact SG stellar system within the FG system. Interestingly, about 40% of AGB ejecta is from stars that do not belong to the FG system (“external gas accretion”). FG and SG stellar systems have different amplitudes of internal rotation and V∕σ. The mass-density (MSG−ρSG) relation for SG stellar systems can be approximated as ρSG ∝ MSG1.5. There can be a threshold total mass of GC host galaxies (Mth = [5 − 23] × 109 M⊙) beyond which the formation of GCs with compact SG stellar systems is possible. Both the initial baryonic mass fraction and the gas mass fraction in dwarfs are crucial parameters that determine whether or not GCs can contain multiple stellar populations. GCs with compact SG stellar systems are more likely to form in dwarf disks with larger gas mass fractions and higher surface mass densities. Formation of binary GCs with SGs and the subsequent GC merging are clearly seen in some models. The derived external gas-accretion process in FG systems initially consisting of stellar clumps will need to be investigated further in more sophisticated simulations.

scholarly journals Constraining churning and blurring in the Milky Way using large spectroscopic surveys – an exploratory study

2020 ◽  
Vol 493 (1) ◽  
pp. 1419-1433 ◽  
Author(s):  
Sofia Feltzing ◽  
J Bradley Bowers ◽  
Oscar Agertz
Keyword(s):  
Exploratory Study ◽  
Milky Way ◽  
Selection Effects ◽  
Radial Migration ◽  
Elemental Abundances ◽  
Stellar Ages ◽  
C And N ◽  
Red Giant ◽  
Future Work ◽  
Giant Branch Stars

ABSTRACT We have investigated the possibilities to quantify how much stars move in the Milky Way disc due to diffuse processes (blurring) and due to influences from spiral arms and the bar (churning). We assume that the formation radius of a star can be inferred if we know its elemental abundances and age and the metallicity profile of the interstellar medium at the time of the star’s formation. We use data for red giant branch stars from APOGEE DR14, parallaxes from Gaia, and stellar ages based on the C and N abundances. In our sample, we find that half of the stars have experienced some sort of radial migration, 10 per cent likely have suffered only from churning, and a modest 5–7 per cent have never experienced either churning or blurring making them ideal tracers of the original properties of the cool stellar disc. To arrive at these numbers, we imposed the requirement that the stars that are considered to be churned have highly circular orbits. If instead we require that the star has moved away from its formation position and at the same time that its Galactocentric radius at formation did not fall between the apo- and pericentre of its orbit today, we find that about half of the stars have undergone a radial migration. We have thus shown that it is possible to put up a framework to quantify churning and blurring. Future work includes investigations of how selection effects influence the results.

scholarly journals Searching for multiple populations in Ruprecht 106

2021 ◽  
Author(s):  
H Frelijj ◽  
S Villanova ◽  
C Muñoz ◽  
J G Fernández-Trincado
Keyword(s):  
Globular Cluster ◽  
Stellar Population ◽  
Atmospheric Parameters ◽  
Photometric Analysis ◽  
Dynamical Study ◽  
Multiple Populations ◽  
Red Giant ◽  
Definition Of ◽  
Energy Plane ◽  
Giant Branch Stars

Abstract More than a decade has passed since the definition of Globular Cluster (GC) changed, and now we know that they host Multiple Populations (MPs). But few GCs do not share that behaviour and Ruprecht 106 is one of these clusters. We analyzed thirteen member red giant branch stars using spectra in the wavelength range 6120-6405 Å obtained through the GIRAFFE Spectrograph, mounted at UT2 telescope at Paranal, as well as the whole cluster using C, V, R and I photometry obtained through the Swope telescope at Las Campanas. Atmospheric parameters were determined from the photometry to determine Fe and Na abundances. A photometric analysis searching for MPs was also carried out. Both analyses confirm that Ruprecht 106 is indeed one on the few GCs to host Simple Stellar Population, in agreement with previous studies. Finally, a dynamical study concerning its orbits was carried out to analyse the possible extragalactic origin of the Cluster. The orbital integration indicates that this GC belongs to the inner halo, while an Energy plane shows that it cannot be accurately associated with any known extragalactic progenitor.

scholarly journals Abundances of Na, Mg, and K in the atmospheres of red giant branch stars of Galactic globular cluster 47 Tucanae

2017 ◽  
Vol 604 ◽  
pp. A35 ◽  
Author(s):  
A. Černiauskas ◽  
A. Kučinskas ◽  
J. Klevas ◽  
D. Prakapavičius ◽  
S. Korotin ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Red Giant ◽  
Giant Branch Stars

scholarly journals Chemical abundance analysis of red giant branch stars in the globular cluster E3

2018 ◽  
Vol 616 ◽  
pp. A181 ◽  
Author(s):  
L. Monaco ◽  
S. Villanova ◽  
G. Carraro ◽  
A. Mucciarelli ◽  
C. Moni Bidin
Keyword(s):  
Radial Velocity ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Abundance Ratio ◽  
Chemical Abundance ◽  
Chemical Abundances ◽  
Multiple Populations ◽  
Red Giant ◽  
A Minor ◽  
Giant Branch Stars

Context. Globular clusters are known to host multiple stellar populations, which are a signature of their formation process. The globular cluster E3 is one of the few low-mass globulars that is thought not to host multiple populations. Aims. We investigate red giant branch stars in E3 with the aim of providing a first detailed chemical inventory for this cluster, we determine its radial velocity, and we provide additional insights into the possible presence of multiple populations in this cluster. Methods. We obtained high-resolution FLAMES-UVES/VLT spectra of four red giant branch stars likely members of E3. We performed a local thermodynamic equilibrium abundance analysis based on one-dimensional plane parallel ATLAS9 model atmospheres. Abundances were derived from line equivalent widths or spectrum synthesis. Results. We measured abundances of Na and of iron peak (Fe, V, Cr, Ni, Mn), α(Mg, Si, Ca, Ti), and neutron capture elements (Y, Ba, Eu). The mean cluster heliocentric radial velocity, metallicity, and sodium abundance ratio are νhelio = 12.6 ± 0.4 km s−1(σ = 0.6 ± 0.2 km s−1), [Fe/H] = −0.89 ± 0.08 dex, and [Na/Fe] = 0.18 ± 0.07 dex, respectively. The low Na abundance with no appreciable spread is suggestive of a cluster dominated by first-generation stars in agreement with results based on lower resolution spectroscopy. The low number of stars observed does not allow us to rule out a minor population of second-generation stars. The observed chemical abundances are compatible with the trends observed in Milky Way stars.

scholarly journals STAR-TO-STAR IRON ABUNDANCE VARIATIONS IN RED GIANT BRANCH STARS IN THE GALACTIC GLOBULAR CLUSTER NGC 3201

2013 ◽  
Vol 764 (1) ◽  
pp. L7 ◽  
Author(s):  
Jennifer Simmerer ◽  
Inese I. Ivans ◽  
Dan Filler ◽  
Patrick Francois ◽  
Corinne Charbonnel ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Iron Abundance ◽  
Red Giant ◽  
Giant Branch Stars

scholarly journals Roche Instability in Ejecting Stellar Systems

1993 ◽  
Vol 132 ◽  
pp. 209-216
Author(s):  
K.S.V.S. Narasimhan ◽  
S.M. Alladin
Keyword(s):  
Density Ratio ◽  
Stellar System ◽  
Impulse Approximation ◽  
Stellar Systems ◽  
Mass Ratio ◽  
Roche Limit ◽  
Mass Ratios ◽  
Two Systems ◽  
Density Ratios ◽  
Scale Length

AbstractWe consider a small stellar system ejected from the interior of a bigger one. The two systems are represented by unequal Plummer models and energy changes in them are derived analytically under the impulse approximation. These are used to obtain the conditions for the Roche instability of the systems. For systems greatly differing in dimension, the density ratio of the two systems is a useful parameter for specifying the Roche limit for the disruption of the smaller system and the mass ratio is a meaningful parameter for specifying the Roche limit for the disruption of the bigger system. Density ratios and mass ratios at Roche limit are given for both systems for various scale-length ratios of the two systems.

scholarly journals Ultra-compact Dwarf Galaxies: a New Class of Compact Stellar System Discovered in the Fornax Cluster

2002 ◽  
Vol 207 ◽  
pp. 287-293
Author(s):  
Michael Drinkwater ◽  
Kenji Bekki ◽  
Warrick Couch ◽  
Steve Phillipps ◽  
Bryn Jones ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Dwarf Galaxies ◽  
Stellar System ◽  
Stellar Systems ◽  
New Class ◽  
Cluster Of Galaxies ◽  
Magnitude Range ◽  
Fornax Cluster

We have used the 2dF spectrograph on the Anglo-Australian Telescope to obtain a complete spectroscopic sample of all objects in the magnitude range, 16.5 < bJ < 19.8, regardless of morphology, in an area centred on the Fornax Cluster of galaxies. Among the unresolved targets are five objects which are members of the Fornax Cluster. They are extremely compact stellar systems with scale lengths less than 40 parsecs. These ultra-compact dwarfs are unlike any known type of stellar system, being more compact and significantly less luminous than other compact dwarf galaxies, yet much brighter than any globular cluster.

Sign in / Sign up

Export Citation Format

Share Document