The GOTHAM survey: chemical evolution of Milky Way globular clusters

2017 ◽  
Vol 13 (S334) ◽  
pp. 25-28
Author(s):  
Bruno Dias ◽  
Beatriz Barbuy ◽  
Ivo Saviane ◽  
Enrico V. Held ◽  
Gary Da Costa ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Stellar Population ◽  
Milky Way ◽  
Open Clusters ◽  
Giant Stars ◽  
Globular Cluster System ◽  
Galactic Globular Clusters ◽  
Red Giant

AbstractMilky Way globular clusters are excellent laboratories for stellar population detailed analysis that can be applied to extragalactic environments with the advent of the 40m-class telescopes like the ELT. The globular cluster population traces the early evolution of the Milky Way which is the field of Galactic archaeology. We present our GlObular clusTer Homogeneous Abundance Measurement (GOTHAM) survey. We derived radial velocities, Teff, log(g), [Fe/H], [Mg/Fe] for red giant stars in one third of all Galactic globular clusters that represent well the Milky Way globular cluster system in terms of metallicity, mass, reddening, and distance. Our method is based on low-resolution spectroscopy and is intrinsically reddening free and efficient even for faint stars. Our [Fe/H] determinations agree with high-resolution results to within 0.08 dex. The GOTHAM survey provides a new metallicity scale for Galactic globular clusters with a significant update of metallicities higher than [Fe/H] > -0.7. We show that the trend of [Mg/Fe] with metallicity is not constant as previously found, because now we have more metal-rich clusters. Moreover, peculiar clusters whose [Mg/Fe] does not match Galactic stars for a given metallicity are discussed. We also measured the CaII triplet index for all stars and we show that the different chemical evolution of Milky Way open clusters, field stars, and globular clusters implies different calibrations of calcium triplet to metallicity.

scholarly journals An Overview of the Globular Cluster System of the Galaxy

1988 ◽  
Vol 126 ◽  
pp. 37-48
Author(s):  
Robert Zinn
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Galactic Center ◽  
Galactic Plane ◽  
Cluster System ◽  
Open Clusters ◽  
The Galaxy ◽  
Globular Cluster System ◽  
Harlow Shapley

Harlow Shapley (1918) used the positions of globular clusters in space to determine the dimensions of our Galaxy. His conclusion that the Sun does not lie near the center of the Galaxy is widely recognized as one of the most important astronomical discoveries of this century. Nearly as important, but much less publicized, was his realization that, unlike stars, open clusters, HII regions and planetary nebulae, globular clusters are not concentrated near the plane of the Milky Way. His data showed that the globular clusters are distributed over very large distances from the galactic plane and the galactic center. Ever since this discovery that the Galaxy has a vast halo containing globular clusters, it has been clear that these clusters are key objects for probing the evolution of the Galaxy. Later work, which showed that globular clusters are very old and, on average, very metal poor, underscored their importance. In the spirit of this research, which started with Shapley's, this review discusses the characteristics of the globular cluster system that have the most bearing on the evolution of the Galaxy.

scholarly journals OCCASO – III. Iron peak and α elements of 18 open clusters. Comparison with chemical evolution models and field stars

2019 ◽  
Vol 490 (2) ◽  
pp. 1821-1842 ◽  
Author(s):  
L Casamiquela ◽  
S Blanco-Cuaresma ◽  
R Carrera ◽  
L Balaguer-Núñez ◽  
C Jordi ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Open Cluster ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Chemical Abundances ◽  
Homogeneous Sample ◽  
Giant Stars ◽  
Stellar Nucleosynthesis ◽  
Solar Abundances ◽  
Red Giant

ABSTRACT The study of open-cluster chemical abundances provides insights on stellar nucleosynthesis processes and on Galactic chemo-dynamical evolution. In this paper we present an extended abundance analysis of 10 species (Fe, Ni, Cr, V, Sc, Si, Ca, Ti, Mg, O) for red giant stars in 18 OCCASO clusters. This represents a homogeneous sample regarding the instrument features, method, line list and solar abundances from confirmed member stars. We perform an extensive comparison with previous results in the literature, and in particular with the Gaia FGK Benchmark stars Arcturus and $\mu$-Leo. We investigate the dependence of [X/Fe] with metallicity, Galactocentric radius (6.5 kpc < RGC < 11 kpc), age (0.3 Gyr < Age < 10 Gyr), and height above the plane (|z| < 1000 pc). We discuss the observational results in the chemo-dynamical framework, and the radial migration impact when comparing with chemical evolution models. We also use APOGEE DR14 data to investigate the differences between the abundance trends in RGC and |z| obtained for clusters and for field stars.

scholarly journals The multipopulation phenomenon in Galactic globular clusters: M4 and M22

2009 ◽  
Vol 5 (S266) ◽  
pp. 326-332
Author(s):  
S. Villanova ◽  
G. Piotto ◽  
A. F. Marino ◽  
A. P. Milone ◽  
A. Bellini ◽  
...  
Keyword(s):  
High Resolution ◽  
Spectroscopic Data ◽  
Globular Clusters ◽  
Stellar Population ◽  
The Other ◽  
Wide Field ◽  
Galactic Globular Clusters ◽  
Red Giant ◽  
Process Elements ◽  
Different Characteristics

AbstractWe present an abundance analysis based on high-resolution spectra of red-giant-branch (RGB) stars in the Galactic globular clusters NGC 6121 (M4) and NGC 6656 (M22). Our aim was to study their stellar population in the context of the multipopulation phenomenon recently discovered to affect some globular clusters. Analysis was performed for the following elements: O, Na, Mg, Al, Ca, Fe, Y, and Ba. Spectroscopic data were completed by high-precision wide-field U BV IC ground-based photometry and HST/ACS observations. For M4, we find a well-defined Na–O anticorrelation composed of two distinct groups of stars with significantly different Na and O content. The two groups of Na-rich and Na-poor stars populate two different regions along the RGB. As regards M22, Na and O follow the well-known anticorrelation found in many other GCs. However, at odds with M4, it appears to be continuous without any hint of clumpiness. On the other hand, we identified two clearly separated groups of stars with significantly different abundances of the s-process elements Y, Zr and Ba. The relative numbers of the members of both groups are very similar to the ratio of the stars in the two subgiant branches of M22 recently found by Piotto (2009). The s-element-rich stars are also richer in iron and have higher Ca abundances. This makes M22 the second cluster after ω Centauri where an intrinsic spread in Fe was found. Both spectroscopic and photometric results imply the presence of two stellar populations in M4 and M22, even if both clusters have completely different characteristics.

scholarly journals Facing problems in the determination of stellar temperatures and gravities: Galactic globular clusters

2020 ◽  
Vol 640 ◽  
pp. A87 ◽  
Author(s):  
A. Mucciarelli ◽  
P. Bonifacio
Keyword(s):  
Low Temperatures ◽  
Globular Clusters ◽  
Simple Relation ◽  
Spectroscopic Parameters ◽  
Giant Stars ◽  
Excitation Potential ◽  
Galactic Globular Clusters ◽  
Stellar Temperatures ◽  
Red Giant ◽  
Photometric Scale

We analysed red giant branch stars in 16 Galactic globular clusters, computing their atmospheric parameters both from the photometry and from excitation and ionisation balances. The spectroscopic parameters are lower than the photometric ones and this discrepancy increases with decreasing metallicity, reaching differences of ~350 K in effective temperature and ~1 dex in surface gravity at [Fe/H] ~ –2.5 dex. We demonstrate that the spectroscopic parameters are inconsistent with the position of the stars in the colour-magnitude diagram, providing overly low temperatures and gravities, and predicting that the stars are up to about 2.5 magnitudes brighter than the observed magnitudes. The parameter discrepancy is likely due to inadequacies in the adopted physics; in particular the assumption of a one-dimensional geometry could be the origin of the observed slope between iron abundances and excitation potential that leads to low temperatures. However, the current modelling of 3D/NLTE radiative transfer for giant stars seems to be unable to totally erase this slope. We conclude that the spectroscopic parameters are incorrect for metallicity lower than –1.5 dex and that photometric temperatures and gravities should be adopted for these red giant stars. We provide a simple relation to correct the spectroscopic temperatures in order to put them onto a photometric scale.

The evolution of the Milky Way’s radial metallicity gradient as seen by APOGEE, CoRoT, and Gaia

2018 ◽  
Vol 14 (A30) ◽  
pp. 257-257
Author(s):  
Friedrich Anders ◽  
Ivan Minchev ◽  
Cristina Chiappini
Keyword(s):  
Milky Way ◽  
Past History ◽  
Open Clusters ◽  
Dynamical Models ◽  
Giant Stars ◽  
The Past ◽  
The Status ◽  
History Of ◽  
Abundance Profile ◽  
Red Giant

AbstractThe time evolution of the radial metallicity gradient is one of the most important constraints for Milky Way chemical and chemo-dynamical models. In this talk we reviewed the status of the observational debate and presented a new measurement of the age dependence of the radial abundance gradients, using combined asteroseismic and spectroscopic observations of red giant stars. We compared our results to state-of-the-art chemo-dynamical Milky Way models and recent literature results obtained with open clusters and planetary nebulae, and propose a new method to infer the past history of the Galactic radial abundance profile.

scholarly journals NGC 5128: The Giant Beneath

2010 ◽  
Vol 27 (4) ◽  
pp. 475-481 ◽  
Author(s):  
Gretchen L. H. Harris
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Stellar Population ◽  
Total Population ◽  
Elliptical Galaxy ◽  
Cluster System ◽  
Fundamental Plane ◽  
Galaxy Type ◽  
Globular Cluster System ◽  
Distance Indicators

AbstractThis paper reviews what has been learned about the old stellar population of NGC 5128, the only large elliptical galaxy close enough that we can currently observe individual stars as faint as the horizontal branch. Although its galaxy type is still a matter of debate, the uncertainties over distance are now largely resolved; comparison of five stellar distance indicators gives d= 3.8±0.1 Mpc. The globular cluster system, which was once perplexingly invisible, is now known to be predominantly old with a substantial metal-rich component. The globular cluster system (GCS) total population and luminosity function are normal and the clusters follow the same fundamental plane relation as those in the Milky Way and M31. Finally, the halo out to at least ∼7reff is dominated by metal-rich stars which are also predominantly old, with age and metallicity tantalizingly similar to the majority of globular clusters.

scholarly journals Spectroscopy of the Globular Clusters in M87

1987 ◽  
Vol 127 ◽  
pp. 451-452
Author(s):  
J.R. Mould ◽  
J.B. Oke ◽  
J.M. Nemec
Keyword(s):  
Density Distribution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Cluster System ◽  
Hot Gas ◽  
The Mean ◽  
Globular Cluster System ◽  
Young Clusters

With a velocity dispersion of 370 ± 50 km/sec the globular cluster system of M87 is kinematically hotter than the stars in the giant elliptical itself. This is consistent with the clusters' shallower density distribution for isotropic orbits. the mean metallicity of the 27 clusters in the sample analyzed here is no more than a factor of 2 more metal rich than the cluster system of the Milky Way, but considerably more metal poor than the integrated starlight in the field at a radius of 1' from the center of M87. There is no evidence for the existence of young clusters in the system. the mass-radius relation between 1' and 5' required to contain the globular clusters joins on to that required to contain the hot gas around M87.

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.

scholarly journals Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code – II. The Southern clusters and overview

2019 ◽  
Vol 492 (2) ◽  
pp. 1641-1670 ◽  
Author(s):  
Szabolcs Mészáros ◽  
Thomas Masseron ◽  
D A García-Hernández ◽  
Carlos Allende Prieto ◽  
Timothy C Beers ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Continuous Distribution ◽  
Data Set ◽  
Giant Stars ◽  
The Third ◽  
Cluster Mass ◽  
Red Giant ◽  
Two Populations ◽  
Homogeneous Data

ABSTRACT We investigate the Fe, C, N, O, Mg, Al, Si, K, Ca, Ce, and Nd abundances of 2283 red giant stars in 31 globular clusters from high-resolution spectra observed in both the Northern and Southern hemisphere by the SDSS-IV APOGEE-2 survey. This unprecedented homogeneous data set, largest to date, allows us to discuss the intrinsic Fe spread, the shape, and statistics of Al-Mg and N-C anti-correlations as a function of cluster mass, luminosity, age, and metallicity for all 31 clusters. We find that the Fe spread does not depend on these parameters within our uncertainties including cluster metallicity, contradicting earlier observations. We do not confirm the metallicity variations previously observed in M22 and NGC 1851. Some clusters show a bimodal Al distribution, while others exhibit a continuous distribution as has been previously reported in the literature. We confirm more than two populations in ω Cen and NGC 6752, and find new ones in M79. We discuss the scatter of Al by implementing a correction to the standard chemical evolution of Al in the Milky Way. After correction, its dependence on cluster mass is increased suggesting that the extent of Al enrichment as a function of mass was suppressed before the correction. We observe a turnover in the Mg-Al anticorrelation at very low Mg in ω Cen, similar to the pattern previously reported in M15 and M92. ω Cen may also have a weak K-Mg anticorrelation, and if confirmed, it would be only the third cluster known to show such a pattern.

scholarly journals Near Infrared Photometry of New Galactic Globular Clusters GC 01 and GC 02

2002 ◽  
Vol 207 ◽  
pp. 107-109 ◽  
Author(s):  
J. Borissova ◽  
V. D. Ivanov ◽  
L. Vanzi
Keyword(s):  
Globular Cluster ◽  
Preliminary Report ◽  
Globular Clusters ◽  
Surface Brightness ◽  
Near Infrared ◽  
Infrared Photometry ◽  
Galactic Globular Clusters ◽  
Red Giant ◽  
Best Fit ◽  
Calculated Distance

We present a preliminary report on the first deep near infrared photometry of 2MASS GC 01 and 2MASS GC 02 - new Galactic globular cluster candidates, discovered by the 2MASS. The red giant branch slopes yielded [Fe/H]=-0.42 ± 0.15 dex and [Fe/H]=-0.66 ± 0.17 dex, respectively for GC 01 and GC 02. We estimated the reddening towards GC 01 and GC 02: E(B - V) = 5.36 ± 0.20, and E(B - V) = 4.55 ± 0.17. The calculated distance moduli to the clusters are: (m - M)0 = 13.53 ± 0.27 and (m - M)0 = 14.53 ± 0.31 for GC 01 and GC 02. Our best fit for the radial surface brightness profile of GC 02 yields: lg(rc) = 1.40, lg(rh) = 1.54, lg(rt) = 1.31, and c=1.60. CC 01 is less concentrated: lg(rc) = 1.63, lg(rh) = 1.7, lg(rt) = 1.25, and c=1.41.

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