scholarly journals Multiple populations in integrated light spectroscopy of intermediate-age clusters

2019 ◽  
Vol 489 (1) ◽  
pp. L80-L85 ◽  
Author(s):  
Nate Bastian ◽  
Christopher Usher ◽  
Sebastian Kamann ◽  
Carmela Lardo ◽  
Søren S Larsen ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Light Element ◽  
Large Magellanic Cloud ◽  
Element Abundance ◽  
Multiple Populations ◽  
Individual Stars ◽  
Abundance Patterns ◽  
Nearby Galaxies ◽  
Massive Clusters ◽  
Light Element Abundance

ABSTRACT The presence of star-to-star light-element abundance variations (also known as multiple populations, MPs) appears to be ubiquitous within old and massive clusters in the Milky Way and all studied nearby galaxies. Most previous studies have focused on resolved images or spectroscopy of individual stars, although there has been significant effort in the past few years to look for multiple population signatures in integrated light spectroscopy. If proven feasible, integrated light studies offer a potential way to vastly open parameter space, as clusters out to 10s of Mpc can be studied. We use the Na D lines in the integrated spectra of two clusters with similar ages (2–3 Gyr) but very different masses: NGC 1978 (∼3 × 105 M⊙) in the Large Magellanic Cloud and G114 (1.7 × 107 M⊙) in NGC 1316. For NGC 1978, our findings agree with resolved studies of individual stars that did not find evidence for Na spreads. However, for G114, we find clear evidence for the presence of multiple populations. The fact that the same anomalous abundance patterns are found in both the intermediate age and ancient globular clusters lends further support to the notion that young massive clusters are effectively the same as the ancient globular clusters, only separated in age.

scholarly journals Light element abundance inhomogeneities in globular clusters: probing star formation and evolution in the early Milky Way

1994 ◽  
Vol 72 (11-12) ◽  
pp. 772-781 ◽  
Author(s):  
Michael M. Briley ◽  
Roger A. Bell ◽  
James E. Hesser ◽  
Graeme H. Smith
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Main Sequence ◽  
Light Element ◽  
Star Formation History ◽  
Element Abundance ◽  
Chemical Compositions ◽  
Original Material ◽  
Abundance Patterns ◽  
Red Giant

Abundance patterns of the elements C, N, and O are sensitive probes of stellar nucleosynthesis processes and, in addition, O abundances are an important input for stellar age determinations. Understanding the nature of the observed distribution of these elements is key to constraining protogalactic star formation history. Patterns deduced from low-resolution spectroscopy of the CN, CH, NH, and CO molecules for low-mass stars in their core-hydrogen or first shell-hydrogen burning phases in the oldest ensembles known, the Galactic globular star clusters, are reviewed. New results for faint stars in NGC 104 (47 Tuc, C0021-723) reveal that the bimodal, anticorrelated pattern of CN and CH strengths found among luminous evolved stars is also present in stars nearing the end of their main-sequence lifetimes. In the absence of known mechanisms to mix newly synthesized elements from the interior to the observable surface layers of such unevolved stars, those particular inhomogeneities imply that the original material from which the stars formed some 15 billion years ago was chemically inhomogeneous in the C and N elements. However, in other clusters, observations of abundance ratios and C isotope ratios suggest that alterations to surface chemical compositions are produced as stars evolve from the main sequence through the red giant branch. Thus, the current observed distributions of C, N, and O among the brightest stars (those also observed most often) may not reflect the true distribution from which the protocluster cloud formed. The picture that is emerging of the C, N, and O abundance patterns within globular clusters may be one which requires a complicated combination of stellar evolutionary and primordial effects for its explanation.

scholarly journals Integrated spectroscopy of extragalactic Globular Clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 155-160
Author(s):  
Charli M. Sakari
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Light Element ◽  
Element Abundance ◽  
Future Perspectives ◽  
Host Galaxies ◽  
Chemical Abundances ◽  
Essential Information ◽  
Light Element Abundance ◽  
Detailed Chemical

AbstractIntegrated light (IL) spectroscopy enables studies of stellar populations beyond the Milky Way and its nearest satellites. In this paper, I will review how IL spectroscopy reveals essential information about globular clusters and the assembly histories of their host galaxies, concentrating particularly on the metallicities and detailed chemical abundances of the GCs in M31. I will also briefly mention the effects of multiple populations on IL spectra, and how observations of distant globular clusters help constrain the source(s) of light-element abundance variations. I will end with future perspectives, emphasizing how IL spectroscopy can bridge the gap between Galactic and extragalactic astronomy.

scholarly journals Leveraging HST with MUSE – I. Sodium abundance variations within the 2-Gyr-old cluster NGC 1978

2020 ◽  
Vol 498 (3) ◽  
pp. 4472-4480
Author(s):  
S Saracino ◽  
S Kamann ◽  
C Usher ◽  
N Bastian ◽  
S Martocchia ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Large Magellanic Cloud ◽  
Host Galaxy ◽  
Very Large Telescope ◽  
Nearby Galaxies ◽  
Red Giant ◽  
Sodium Abundance ◽  
Massive Clusters ◽  
Cluster Age

ABSTRACT Nearly all of the well-studied ancient globular clusters (GCs), in the Milky Way and in nearby galaxies, show star-to-star variations in specific elements (e.g. He, C, N, O, Na, and Al), known as ‘multiple populations’ (MPs). However, MPs are not restricted to ancient clusters, with massive clusters down to ∼2 Gyr showing signs of chemical variations. This suggests that young and old clusters share the same formation mechanism but most of the work to date on younger clusters has focused on N variations. Initial studies even suggested that younger clusters may not host spreads in other elements beyond N (e.g. Na), calling into question whether these abundance variations share the same origin as in the older GCs. In this work, we combine Hubble Space Telescope (HST) photometry with Very Large Telescope (VLT)/Multi-Unit Spectroscopic Explorer (MUSE) spectroscopy of a large sample of red giant branch (RGB) stars (338) in the Large Magellanic Cloud cluster NGC 1978, the youngest globular to date with reported MPs in the form of N spreads. By combining the spectra of individual RGB stars into N-normal and N-enhanced samples, based on the ‘chromosome map’ derived from HST, we search for mean abundance variations. Based on the NaD line, we find a Na difference of Δ[Na/Fe] = 0.07 ± 0.01 between the populations. While this difference is smaller than typically found in ancient GCs (which may suggest a correlation with age), this result further confirms that the MP phenomenon is the same, regardless of cluster age and host galaxy. As such, these young clusters offer some of the strictest tests for theories on the origin of MPs.

scholarly journals Rediscovering the origins of the stellar halo with chemical tagging

2017 ◽  
Vol 13 (S334) ◽  
pp. 38-42 ◽  
Author(s):  
Sarah L Martell
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Galactic Halo ◽  
Light Element ◽  
Element Abundance ◽  
Tidal Interactions ◽  
Halo Stars ◽  
The Galaxy ◽  
Stellar Halo ◽  
Light Element Abundance

AbstractThe Galactic halo has a complex assembly history, which can be seen in its wealth of kinematic and chemical substructure. Globular clusters lose stars through tidal interactions with the Galaxy and cluster evaporation processes, meaning that they are inevitably a source of halo stars. These “migrants” from globular clusters can be recognized in the halo field by the characteristic light element abundance anticorrelations that are commonly observed only in globular cluster stars, and the number of halo stars that can be chemically tagged to globular clusters can be used to place limits on the formation pathways of those clusters.

Light‐Element Abundance Patterns in the Orion Association. I.Hubble Space TelescopeObservations of Boron in G Dwarfs

2000 ◽  
Vol 543 (2) ◽  
pp. 850-860 ◽  
Author(s):  
Katia Cunha ◽  
Verne V. Smith ◽  
Etienne Parizot ◽  
David L. Lambert
Keyword(s):  
Light Element ◽  
Element Abundance ◽  
Abundance Patterns ◽  
Orion Association ◽  
Light Element Abundance

scholarly journals Breaking the dichotomy between typical and anomalous globular clusters: the case of NGC 3201

2019 ◽  
Vol 14 (S351) ◽  
pp. 293-296
Author(s):  
Bruno Dias ◽  
Ignacio Araya ◽  
João Paulo Nogueira-Cavalcante ◽  
Leila Saker ◽  
Ahmed Shokry
Keyword(s):  
Strong Evidence ◽  
Globular Clusters ◽  
Classification Scheme ◽  
Dwarf Galaxies ◽  
Light Element ◽  
Element Abundance ◽  
Mass Size ◽  
Process Element ◽  
Size Relation ◽  
Light Element Abundance

AbstractWe recently discovered that NGC 3201 has characteristics that set it outside the current twofold classification scheme for Galactic globular clusters (GCs). Most GCs are mono-metallic and show light-element abundance variations (e.g., Na-O and C-N anti-correlations); but a minority of clusters also present variations in Fe correlating with s-process element and C+N+O abundances, and they possess multiple C-N sequences. These anomalous GCs also have a broad sub-giant branch (SGB) and follow the same mass-size relation as dwarf galaxies possibly evolving into GCs. We now revealed that NGC 3201 belongs to neither group. It has multiple C-N sequences, but no broad SGB, no strong evidence of a Fe-spread, and it does not follow the mass-size relation.

scholarly journals UV-Observations of Young Populous Clusters in the Large Magellanic Cloud

1984 ◽  
Vol 108 ◽  
pp. 55-56
Author(s):  
Edward H. Geyer ◽  
Angelo Cassatella
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Large Magellanic Cloud ◽  
Time Interval ◽  
Sequence Evolution ◽  
Stellar Clusters ◽  
T Tauri ◽  
Red Supergiants ◽  
Evolution Phase ◽  
Massive Clusters

The young populous star clusters give evidence for the ‘explosive’ star formation in the Magellanic Clouds which took place in the time interval 5·106 yrs to < 108 yrs agoe. They are also key objects for the understanding of the formation of massive stellar clusters, because they are still situated close to their ‘birthplace’ in the parent galaxy and are dynamically not relaxed (Geyer et al. 1979). Their HRD-morphology shows most of the member stars in the upper Main Sequence range with only a few massive yellow and red supergiants. The lower massive stars are still in the pre-main-sequence evolution phase (‘T-Tauri state’), which cannot be observed at the MC's distances. Thus in the uv-spectral range the blue stars with (B-V) < 0.1 on the upper MS contribute to the uv-fluxes. In the optical spectral regions the bright ‘blue’ globular clusters seem not be embedded in remanent interstellar matter, though neighbouring loose stellar aggregates of similar age are in many cases surrounded by dense HII-regions. This rises the questions wether the starformation process in such massive clusters was so efficient that no remanent matter was left over, or was this material blown away by the uv-radiation of the numerous OB-member stars?

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