scholarly journals Kinematics of outer halo globular clusters: M 75 and NGC 6426

2018 ◽  
Vol 616 ◽  
pp. A74 ◽  
Author(s):  
Andreas Koch ◽  
Michael Hanke ◽  
Nikolay Kacharov
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
High Resolution Spectroscopy ◽  
Large Uncertainty ◽  
Dynamic Interactions ◽  
A Value ◽  
Kinematic Study ◽  
Younger Age ◽  
Low Metallicity ◽  
Insight Into

Globular clusters (GCs) and their dynamic interactions with the Galactic components provide an important insight into the structure and formation of the early Milky Way. We present a kinematic study of two outer halo GCs based on a combination of VLT/FORS2, VLT/FLAMES, and Magellan/MIKE low- and high-resolution spectroscopy of 32 and 27 member stars, respectively. Although both clusters are located at Galactocentric distances of 15 kpc, they have otherwise very different properties. M 75 is a luminous and metal-rich system at [Fe/H] = −1.2 dex, which is a value that we confirm from the calcium triplet region. This GC shows mild evidence for rotation with an amplitude of Arot ~ 5 km s−1. One of the most metal-poor GCs in the Milky Way (at [Fe II/H] = −2.3 dex), NGC 6426 exhibits marginal evidence of internal rotation at the 2 km s−1 level. Both objects have velocity dispersions that are consistent with their luminosity. Although limited by small-number statistics, the resulting limits on their Arot/σ0 ratios suggest that M 75 is a slow rotator driven by internal dynamics rather than being affected by the weak Galactic tides at its large distances. In this work, M 75 (Arot/σ0 = 0.31) is fully consistent with the properties of other, younger halo clusters. At Arot/σ0 = 0.8 ± 0.4, NGC 6426 appears to have a remarkably ordered internal motion for its low metallicity, but the large uncertainty does not allow for an unambiguous categorization as a fast rotator. An accretion origin of M 75 cannot be excluded, based on the eccentric orbit, which we derived from the recent data release 2 of Gaia, and considering its younger age.

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 IC 4499 revised: Spectro-photometric evidence of small light-element variations

2018 ◽  
Vol 618 ◽  
pp. A131 ◽  
Author(s):  
E. Dalessandro ◽  
C. Lardo ◽  
M. Cadelano ◽  
S. Saracino ◽  
N. Bastian ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Light Element ◽  
High Resolution Spectroscopy ◽  
Multiple Populations ◽  
Number Ratio ◽  
Red Giant ◽  
Good Agreement

It has been suggested that IC 4499 is one of the very few old globulars to not host multiple populations with light-element variations. To follow-up on this very interesting result, here we have made use of accurate HST photometry and FLAMES at VLT high-resolution spectroscopy to investigate in more detail the stellar population properties of this system. We find that the red giant branch of the cluster is clearly bimodal in near-UV-optical colour-magnitude diagrams, thus suggesting that IC 4499 is actually composed by two sub-populations of stars with different nitrogen abundances. This represents the first detection of multiple populations in IC 4499. Consistently, we also find that one star out of six is Na-rich to some extent, while we do not detect any evidence of intrinsic spread in both Mg and O. The number ratio between stars with normal and enriched nitrogen is in good agreement with the number ratio – mass trend observed in Galactic globular clusters. Also, as typically found in other systems, nitrogen rich stars are more centrally concentrated than normal stars, although this result cannot be considered conclusive because of the limited field of view covered by our observations (∼1rh). On the contrary, we observe that both the RGB UV colour spread, which is a proxy of N variations, and Na abundance variations, are significantly smaller than those observed in Milky Way globular clusters with mass and metallicity comparable to IC 4499. The modest N and Na spreads observed in this system can be tentatively connected to the fact that IC 4499 likely formed in a disrupted dwarf galaxy orbiting the Milky Way, as previously proposed based on its orbit.

scholarly journals The likelihood of undiscovered globular clusters in the outskirts of the Milky Way

2021 ◽  
Vol 502 (3) ◽  
pp. 4547-4557
Author(s):  
Jeremy J Webb ◽  
Raymond G Carlberg
Keyword(s):  
Equilibrium State ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Expected Number ◽  
Galactocentric Distance ◽  
Deep Imaging ◽  
Low Metallicity ◽  
Globular Cluster System ◽  
Kinematic Properties

ABSTRACT The currently known Galactic globular cluster population extends out to a maximum galactocentric distance of ∼145 kpc, with the peculiarity that the outermost clusters predominantly have an inward velocity. Orbit averaging finds that this configuration occurs by chance about $6{{\ \rm per\ cent}}$ of the time, suggesting that several globular clusters with positive radial velocities remain undiscovered. We evaluate the expected number of undiscovered clusters at large distances under the assumption that the cluster population has a smooth radial distribution and is in equilibrium within the Milky Way’s virial radius. By comparing the present day kinematic properties of outer clusters to random orbital configurations of the Galactic globular cluster system through orbit averaging, we estimate a likelihood of $73{{\ \rm per\ cent}}$ of there being at least one undiscovered globular cluster within the Milky Way. This estimate assumes the current population is complete out to 50 kpc, and increases to $91{{\ \rm per\ cent}}$ if the population is complete out to 150 kpc. The likelihood of there being two undiscovered clusters is between $60$ and $70{{\ \rm per\ cent}}$, with the likelihood of there being three undiscovered clusters being on the order of $50{{\ \rm per\ cent}}$. The most likely scenario is that the undiscovered clusters are moving outwards, which results in the outer cluster population being consistent with an equilibrium state. Searches for distant and possibly quite low concentration and very low metallicity globular clusters will be enabled with upcoming deep imaging surveys.

Revision of the [Fe/H] – φ31–Prelationship for RRc variables

2013 ◽  
Vol 9 (S301) ◽  
pp. 461-462
Author(s):  
Siobahn Morgan
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Fourier Coefficients ◽  
Rr Lyrae ◽  
Best Fitting ◽  
Low Metallicity ◽  
Type C ◽  
Galactic Globular Clusters ◽  
The Relationship

AbstractThe relationship derived by Morganet al. (2007) for type-c RR Lyrae variables (RRc) between values of [Fe/H] – φ31–Phas been revised and expanded. New relationships are based upon Fourier coefficients of 163 RRc variables in 19 Galactic globular clusters using the metallicity scales of Harris (2010), Zinn & West (1984) and Carrettaet al. (2009). This larger database includes more low-metallicity clusters ([Fe/H] < −2.0), and the best fitting relations are found to depend upon values of logPrather thanP. The new relations are applied to various populations of RRc including Milky Way field variables, LMC globular clusters variables, ω Cen RRc, and RRc in various OGLE III databases.

scholarly journals The Pristine Survey – VIII. The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime

2020 ◽  
Vol 492 (4) ◽  
pp. 4986-5002 ◽  
Author(s):  
K Youakim ◽  
E Starkenburg ◽  
N F Martin ◽  
G Matijevič ◽  
D S Aguado ◽  
...  
Keyword(s):  
Distribution Function ◽  
Globular Clusters ◽  
Milky Way ◽  
Current Data ◽  
Low Latitude ◽  
Chemical Enrichment ◽  
Merger Event ◽  
Low Metallicity ◽  
Metallicity Distribution ◽  
Milky Way Halo

ABSTRACT The Pristine survey uses narrow-band photometry to derive precise metallicities down to the extremely metal-poor regime ($ \rm [Fe/H] \lt -3$), and currently consists of over 4 million FGK-type stars over a sky area of $\sim 2500\, \mathrm{deg}^2$. We focus our analysis on a subsample of ∼80 000 main-sequence turn-off stars with heliocentric distances between 6 and 20 kpc, which we take to be a representative sample of the inner halo. The resulting metallicity distribution function (MDF) has a peak at $ \rm [Fe/H] =-1.6$, and a slope of Δ(LogN)/$\Delta \rm [Fe/H] = 1.0 \pm 0.1$ in the metallicity range of $-3.4\; \lt\; \rm [Fe/H]\; \lt -2.5$. This agrees well with a simple closed-box chemical enrichment model in this range, but is shallower than previous spectroscopic MDFs presented in the literature, suggesting that there may be a larger proportion of metal-poor stars in the inner halo than previously reported. We identify the Monoceros/TriAnd/ACS/EBS/A13 structure in metallicity space in a low-latitude field in the anticentre direction, and also discuss the possibility that the inner halo is dominated by a single, large merger event, but cannot strongly support or refute this idea with the current data. Finally, based on the MDF of field stars, we estimate the number of expected metal-poor globular clusters in the Milky Way halo to be 5.4 for $ \rm [Fe/H]\; \lt\; -2.5$ and 1.5 for $ \rm [Fe/H]\; \lt\; -3$, suggesting that the lack of low-metallicity globular clusters in the Milky Way is not due simply to statistical undersampling.

scholarly journals The accreted nuclear clusters of the Milky Way

2020 ◽  
Vol 500 (2) ◽  
pp. 2514-2524
Author(s):  
Joel Pfeffer ◽  
Carmela Lardo ◽  
Nate Bastian ◽  
Sara Saracino ◽  
Sebastian Kamann
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Star Clusters ◽  
Host Galaxy ◽  
The Galaxy ◽  
Nuclear Clusters ◽  
The Common ◽  
Massive Clusters ◽  
Peculiar Case

ABSTRACT A number of the massive clusters in the halo, bulge, and disc of the Galaxy are not genuine globular clusters (GCs) but instead are different beasts altogether. They are the remnant nuclear star clusters (NSCs) of ancient galaxies since accreted by the Milky Way. While some clusters are readily identifiable as NSCs and can be readily traced back to their host galaxy (e.g. M54 and the Sagittarius Dwarf galaxy), others have proven more elusive. Here, we combine a number of independent constraints, focusing on their internal abundances and overall kinematics, to find NSCs accreted by the Galaxy and trace them to their accretion event. We find that the true NSCs accreted by the Galaxy are: M54 from the Sagittarius Dwarf, ω Centari from Gaia-Enceladus/Sausage, NGC 6273 from Kraken, and (potentially) NGC 6934 from the Helmi Streams. These NSCs are prime candidates for searches of intermediate-mass black holes (BHs) within star clusters, given the common occurrence of galaxies hosting both NSCs and central massive BHs. No NSC appears to be associated with Sequoia or other minor accretion events. Other claimed NSCs are shown not to be such. We also discuss the peculiar case of Terzan 5, which may represent a unique case of a cluster–cluster merger.

scholarly journals The effects of different Type Ia SN yields on Milky Way chemical evolution

2021 ◽  
Vol 503 (3) ◽  
pp. 3216-3231
Author(s):  
Marco Palla
Keyword(s):  
Chemical Evolution ◽  
White Dwarf ◽  
Time Distribution ◽  
Milky Way ◽  
Massive Stars ◽  
Abundance Patterns ◽  
Type Ia ◽  
Low Metallicity ◽  
Explosion Mechanism ◽  
Chemical Evolution Model

ABSTRACT We study the effect of different Type Ia SN nucleosynthesis prescriptions on the Milky Way chemical evolution. To this aim, we run detailed one-infall and two-infall chemical evolution models, adopting a large compilation of yield sets corresponding to different white dwarf progenitors (near-Chandrasekar and sub-Chandrasekar) taken from the literature. We adopt a fixed delay time distribution function for Type Ia SNe, in order to avoid degeneracies in the analysis of the different nucleosynthesis channels. We also combine yields for different Type Ia SN progenitors in order to test the contribution to chemical evolution of different Type Ia SN channels. The results of the models are compared with recent LTE and NLTE observational data. We find that ‘classical’ W7 and WDD2 models produce Fe masses and [α/Fe] abundance patterns similar to more recent and physical near-Chandrasekar and sub-Chandrasekar models. For Fe-peak elements, we find that the results strongly depend either on the white dwarf explosion mechanism (deflagration-to-detonation, pure deflagration, double detonation) or on the initial white dwarf conditions (central density, explosion pattern). The comparison of chemical evolution model results with observations suggests that a combination of near-Chandrasekar and sub-Chandrasekar yields is necessary to reproduce the data of V, Cr, Mn and Ni, with different fractions depending on the adopted massive stars stellar yields. This comparison also suggests that NLTE and singly ionized abundances should be definitely preferred when dealing with most of Fe-peak elements at low metallicity.

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.

How to foster employee satisfaction by means of coaching, motivation, emotional salary and social media skills in the agri-food value chain

New Medit ◽  
2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Keyword(s):  
Social Media ◽  
Value Chain ◽  
Employee Satisfaction ◽  
Data Set ◽  
Business Skills ◽  
A Value ◽  
The Social ◽  
Use Of Social Media ◽  
Food Value ◽  
Insight Into

Most employee satisfaction studies do not consider the current digital transformation of the social world. The aim of this research is to provide insight into employee satisfaction in agribusiness by means of coaching, motivation, emotional salary and social media with a value chain methodology. The model is tested empirically by analysing a survey data set of 381 observations in Spanish agribusiness firms of the agri-food value chain. The results show flexible remunerations of emotional salary are determinants of employee satisfaction. Additionally, motivation is relevant in the production within commercialisation link and coaching in the production within transformation link. Whole-of-chain employees showed the greatest satisfaction with the use of social media in personnel management. Findings also confirmed that employees will stay when a job is satisfying. This study contributes to the literature by investigating the effect of current social and digital business skills on employee satisfaction in the agri-food value chain.

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