Dynamical evolution of globular clusters: Recent developments

2017 ◽  
Vol 26 (09) ◽  
pp. 1730017
Author(s):  
Marco Merafina
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Structural Parameters ◽  
Dynamical Evolution ◽  
Limit Value ◽  
Tidal Forces ◽  
The Galaxy ◽  
Recent Developments ◽  
Theoretical Results

We analyze structural parameters of the globular clusters belonging to the Milky Way system which were listed in the latest edition of the Harris Catalogue. We search for observational evidences of the effect of tidal forces induced by the Galaxy on the dynamical and thermodynamical evolution of a globular cluster. The behavior for the [Formula: see text] distribution exhibited by the globular cluster population seems to be in contrast with theoretical results in literature about gravothermal instability, and suggest a new limit value smaller than the previous one.

scholarly journals Characteristic radii of the Milky Way globular clusters

2019 ◽  
Vol 489 (3) ◽  
pp. 4367-4377 ◽  
Author(s):  
Andrés E Piatti ◽  
Jeremy J Webb ◽  
Raymond G Carlberg
Keyword(s):  
Gravitational Field ◽  
Globular Clusters ◽  
Milky Way ◽  
Structural Parameters ◽  
Large Fraction ◽  
Dynamical Evolution ◽  
Initial Mass ◽  
Galactocentric Distance ◽  
Data Set ◽  
Tidal Forces

ABSTRACT We report on the extent of the effects of the Milky Way gravitational field in shaping the structural parameters and internal dynamics of its globular cluster population. We make use of a homogeneous, up-to-date data set with kinematics, structural properties, current and initial masses of 156 globular clusters. In general, cluster radii increase as the Milky Way potential weakens; with the core and Jacobi radii being those which increase at the slowest and fastest rate, respectively. We interpret this result as the innermost regions of globular clusters being less sensitive to changes in the tidal forces with the Galactocentric distance. The Milky Way gravitational field also seems to have differentially accelerated the internal dynamical evolution of individual clusters, with those toward the bulge appearing dynamically older. Finally, we find a subpopulation consisting of both compact and extended globular clusters (as defined by their rh/rJ ratio) beyond 8 kpc that appear to have lost a large fraction of their initial mass lost via disruption. Moreover, we identify a third group with rh/rJ > 0.4, which have lost an even larger fraction of their initial mass by disruption. In both cases the high fraction of mass lost is likely due to their large orbital eccentricities and inclination angles, which lead to them experiencing more tidal shocks at perigalacticon and during disc crossings. Comparing the structural and orbital parameters of individual clusters allows for constraints to be placed on whether or not their evolution was relaxation or tidally dominated.

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 Dynamics of Globular Cluster Systems

1983 ◽  
Vol 100 ◽  
pp. 359-364
Author(s):  
K. C. Freeman
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Cluster Formation ◽  
Active Phase ◽  
Chemical Abundance ◽  
Cluster Systems ◽  
Chemical Enrichment ◽  
Wide Range ◽  
The Galaxy

In the Milky Way, the globular clusters are all very old, and we are accustomed to think of them as the oldest objects in the Galaxy. The clusters cover a wide range of chemical abundance, from near solar down to about [Fe/H] ⋍ −2.3. However there are field stars with abundances significantly lower than −2.3 (eg Bond, 1980); this implies that the clusters formed during the active phase of chemical enrichment, with cluster formation beginning at a time when the enrichment processes were already well under way.

scholarly journals Evolution of the Galactic Globular Cluster System

1996 ◽  
Vol 174 ◽  
pp. 401-402
Author(s):  
E. Vesperini
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Initial Conditions ◽  
Structural Parameters ◽  
Mass Function ◽  
Cluster System ◽  
The Galaxy ◽  
Globular Cluster System ◽  
Individual Cluster

Recent surveys of the observational properties of galactic globular clusters have shown the existence of interesting correlations and trends between structural parameters and between structural parameters and location inside the Galaxy (Chernoff & Djorgovski 1989, Djorgovski & Meylan 1994). The origin of most of these correlations is not clear yet and it is not clear to what extent they reflect the primordial conditions or the result of evolution. We have carried out a set of simulations following the evolution of the properties of a globular cluster system (mass function, spatial distribution, correlations between structural parameters) starting from given initial conditions. The evolution of each individual cluster has been followed by the same method applied by Chernoff et al. (1986) and Chernoff & Shapiro (1987). The effects of internal relaxation, disk shocking and dynamical friction have been considered. The main goal of the analysis is that of establishing the role of initial conditions and evolutionary processes in determining the present observational properties.

Structural parameters for the globular-cluster-like objects in NGC 1052-DF2

2020 ◽  
Vol 496 (3) ◽  
pp. 3741-3754
Author(s):  
Jun Ma ◽  
Shoucheng Wang ◽  
Song Wang ◽  
Zhimin Zhou ◽  
Tianmeng Zhang ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Surface Brightness ◽  
Milky Way ◽  
Hubble Space Telescope ◽  
Structural Parameters ◽  
Star Clusters ◽  
Star Cluster ◽  
Wilson Model ◽  
D 20

ABSTRACT Recently, van Dokkum et al. have found an ultra-diffuse galaxy NGC 1052-DF2 with little or no dark matter, based on a spectroscopic study of its 11 constituent globular-cluster-like objects. In this paper, we analyse these 11 objects using Hubble Space Telescope imaging. We derive the structural parameters for each object by fitting the surface brightness profiles to three different models. Our results indicate that these objects are better fitted by the Wilson model than by the King and Sérsic models. Using the distance of D = 20 Mpc to NGC 1052-DF2 obtained by van Dokkum et al., these 11 objects have half-light radii in the range from ∼11 to ∼16 pc. These values are much larger than for normal globular clusters in the Milky Way, and are comparable to the sizes of an extended star cluster and of a typical ultra-compact dwarf. The half-light radii obtained here are larger than those obtained by van Dokkum et al. and Trujillo et al. The offset of the differences between the half-light radii of van Dokkum et al. and ours is 6.17 pc, and the offset of the differences between the half-light radii of Trujillo et al. and ours is 4.99 pc. Our half-light radii are, on average, 11.74 pc, which corresponds to 53 and 43 per cent larger than those obtained by van Dokkum et al. and Trujillo et al., respectively. The Rh versus MV diagram shows that these objects occupy the same areas of extended star clusters and ultra-compact dwarfs. Using the distance of D = 13 Mpc obtained by Trujillo et al., there are still five objects that do not lie in the area of normal globular clusters in the Milky Way. So, we suggest that these globular-cluster-like objects in NGC 1052-DF2 are not normal globular clusters like those in the Milky Way.

scholarly journals A New Survey of Globular Cluster Structural and Luminosity Parameters

1988 ◽  
Vol 126 ◽  
pp. 489-490
Author(s):  
B. Cameron Reed ◽  
Charles J. Peterson
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Structural Parameters ◽  
Accurate Determination ◽  
Simplex Algorithm ◽  
Photoelectric Photometry ◽  
Central Surface ◽  
The Galaxy ◽  
Photometric Measurements

We have made an analysis of the visual photometric data contained in the Catalogue of Concentric Aperture UBVRI Photoelectric Photometry of Globular Clusters (Peterson 1986). Structural parameters have been obtained by use of the Simplex algorithm of Caceci and Cacheris (1984) to fit the model curves of King (1966) to the run of cluster luminosity with radius. We find that concentric aperture photometry alone can be used to determine globular cluster core radii and central surface brigtnesses reliably. Application of this techique, however, is limited to about two-thirds of the known clusters of the Galaxy because no or inadequate numbers of photometric measurements exist for the remaining clusters. Accurate determination of cluster concentration classes still requires use of other types of data, such as star counts.

Extra-tidal features using Gaia DR2

2019 ◽  
Vol 14 (S351) ◽  
pp. 420-421
Author(s):  
Julio A. Carballo-Bello
Keyword(s):  
Mass Distribution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Space Mission ◽  
Cluster Center ◽  
Proper Motions ◽  
The Galaxy ◽  
Tidal Tails ◽  
Gaia Dr2

AbstractIn recent years, we have gathered enough evidence showing that most of the Galactic globular clusters extend well beyond their King tidal radii and fill their Jacobi radii in the form of “extended stellar haloes”. In some cases, because of the interaction with the Milky Way, stars are able to exceed the Jacobi radius, generating tidal tails which may be used to trace the mass distribution in the Galaxy. In this work, we use the precious information provided by the space mission Gaia (photometry, parallaxes and proper motions) to analyze NGC 362 in the search for member stars in its surroundings. Our preliminar results suggest that it is possible to identify member stars and tidal features up to distances of a few degrees from the globular cluster center.

The contribution of Globular Clusters to the stellar halo using APOGEE and GAIA

2019 ◽  
Vol 14 (S351) ◽  
pp. 455-459
Author(s):  
Danny Horta ◽  
J. Ted Mackereth ◽  
Ricardo P. Schiavon ◽  
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Substantial Fraction ◽  
Data Release ◽  
The Galaxy ◽  
Stellar Halo ◽  
Mass Assembly ◽  
Key Questions

AbstractOver the last decade, much of the key questions in Galactic Archaeology have been asnwered by studying the Milky Way’s globular cluster (GC) system. Following on this, it has been shown that a substantial fraction of the Milky Way’s stellar halo field arises from GC dissolution. In this work, we make use of the latest data release fromn the APOGEE survey to study GC dissolution ratios in different spatial regions of the Galaxy. Our results will allow us to constrain many astrophysical questions, such as: the origin of N-Rich stars, the mass contribution from GCs to the stellar halo of the Galaxy, the origin of the Galactic GC system and the mass assembly of the Milky Way.

scholarly journals The [α/Fe]–[Fe/H] relation in the E-MOSAICS simulations: its connection to the birth place of globular clusters and the fraction of globular cluster field stars in the bulge

2019 ◽  
Vol 491 (3) ◽  
pp. 4012-4022 ◽  
Author(s):  
Meghan E Hughes ◽  
Joel L Pfeffer ◽  
Marie Martig ◽  
Marta Reina-Campos ◽  
Nate Bastian ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Element Abundances ◽  
Field Star ◽  
Wide Range ◽  
The Galaxy ◽  
High Fraction ◽  
The Difference

ABSTRACT The α-element abundances of the globular cluster (GC) and field star populations of galaxies encode information about the formation of each of these components. We use the E-MOSAICS cosmological simulations of ∼L* galaxies and their GCs to investigate the [α/Fe]–[Fe/H] distribution of field stars and GCs in 25 Milky Way–mass galaxies. The [α/Fe]–[Fe/H] distribution of GCs largely follows that of the field stars and can also therefore be used as tracers of the [α/Fe]–[Fe/H] evolution of the galaxy. Due to the difference in their star formation histories, GCs associated with stellar streams (i.e. which have recently been accreted) have systematically lower [α/Fe] at fixed [Fe/H]. Therefore, if a GC is observed to have low [α/Fe] for its [Fe/H] there is an increased possibility that this GC was accreted recently alongside a dwarf galaxy. There is a wide range of shapes for the field star [α/Fe]–[Fe/H] distribution, with a notable subset of galaxies exhibiting bimodal distributions, in which the high [α/Fe] sequence is mostly comprised of stars in the bulge, a high fraction of which are from disrupted GCs. We calculate the contribution of disrupted GCs to the bulge component of the 25 simulated galaxies and find values between 0.3 and 14 per cent, where this fraction correlates with the galaxy’s formation time. The upper range of these fractions is compatible with observationally inferred measurements for the Milky Way, suggesting that in this respect the Milky Way is not typical of L*galaxies, having experienced a phase of unusually rapid growth at early times.

scholarly journals From globular clusters to the disc: the dual life of our Galaxy

2018 ◽  
Vol 620 ◽  
pp. A194 ◽  
Author(s):  
Alejandra Recio-Blanco
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Structural Parameters ◽  
Light Element ◽  
High Mass ◽  
Chemical Abundances ◽  
Element Abundances ◽  
Early Phases ◽  
Poor Population

The halo and disc globular cluster population can be used as a tracer of the primordial epochs of the Milky Way formation. In this work, literature data of globular clusters ages, chemical abundances, and structural parameters are studied, explicitly focussing on the origin of the known split in the age-metallicity relation (AMR) of globular clusters. When the α-element abundances, which are less strongly affected by the internal light-element spread of globular clusters (Si, Ca), are considered, a very low observational scatter among metal-poor clusters is observed. A plateau at [SiCa/Fe],∼ 0.35 dex, with a dispersion of only 0.05 dex (including abundance errors) is observed up to a metallicity of about −0.75 dex. Only a few metal-poor clusters in this metallicity interval present low [SiCa/Fe] abundances. Moreover, metal-rich globular clusters show a knee in the [α/Fe] vs. [Fe/H] plane around [Fe/H] ∼ −0.75 dex. As a consequence, if a substantial fraction of galactic globular clusters has an external origin, they have to be mainly formed either in galaxies that are massive enough to ensure high levels of α-element abundances even at intermediate metallicity, or in lower mass dwarf galaxies accreted by the Milky Way in their early phases of formation. Finally, clusters in the metal-poor branch of the AMR present an anti-correlation of [SiCa/Fe] with the total cluster magnitude, while this is not the case for metal-rich branch clusters. In addition, this lack of faint high-α clusters in the young metal-poor population is in contrast with what is observed for old and more metal-poor clusters, possibly reflecting a higher heterogeneity of formation environments at lower metallicity. Accretion of high-mass satellites, as a major contribution to the current Milky Way globular cluster system both in the metal-poor and the metal-intermediate regime is compatible with the observations.

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