scholarly journals Search for the evolutionary relationship between Galactic globular and open clusters using data from the Gaia DR2 catalogue

2019 ◽  
Vol 488 (3) ◽  
pp. 3474-3481
Author(s):  
A T Bajkova ◽  
V V Bobylev
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Density Wave ◽  
Evolutionary Relationship ◽  
Open Clusters ◽  
Proper Motions ◽  
Galactic Disc ◽  
Disc Bulge ◽  
Using Data ◽  
Gaia Dr2

Abstract Passing through the Galactic disc, a massive object such as a globular cluster, can trigger star formation process leading to the birth of open clusters. Here, we analyse such possible evolutionary relationship between globular and open clusters. To search for the closest rapprochement between objects we computed backwards the orbits of 150 Galactic globular and 232 open clusters (younger than 100 Myr) with proper motions, derived from the Gaia DR2 catalogue. The orbits were computed using the recently modified three-component (disc, bulge, and halo) axisymmetric Navarro–Frenk–White potential, which was complemented by non-axisymmetric bar and spiral density wave potentials. We obtained a new estimate for the frequency of impacts of globular clusters about the Galactic disc, which is equal to four events for 1 Myr. In the framework of the considered scenario, we highlight the following nine pairs of globular and open clusters, with rapprochement within 1 kpc at the time of the intersection the Galactic disc by a globular cluster for the latest 100 Myr: NGC 104 – Turner 3, NGC 104 – NGC 6396, NGC 104 – Ruprecht 127, NGC 5139 – Trumpler 17, NGC 5139 – NGC 6520, NGC 6341 – NGC 6613, NGC 6838 – NGC 6520, NGC 7078 – NGC 7063, NGC 6760 – Ruprecht 127.

Two kinematically different Large Magellanic Cloud old globular cluster populations unveiled from Gaia DR2 data sets

2019 ◽  
Vol 14 (S351) ◽  
pp. 139-142
Author(s):  
Andrés E. Piatti ◽  
Emilio J. Alfaro ◽  
Tristan Cantat-Gaudin
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Data Sets ◽  
Spatial Distributions ◽  
Proper Motions ◽  
Structural Components ◽  
Absolute Value ◽  
Gaia Dr2

AbstractWe derive mean proper motions of 15 known Large Magellanic Cloud (LMC) old globular clusters (GCs) from the Gaia DR2 data sets. When these mean proper motions are gathered with existent radial velocities to compose the GCs’ velocity vectors, we found that the projection of the velocity vectors onto the LMC plane and those perpendicular to it tell us about two distinct kinematical GC populations. Such a distinction becomes clear if the GCs are split at a perpendicular velocity of 10 km/s (absolute value). The two different kinematics groups also exhibit different spatial distributions. Those with smaller vertical velocities are part of the LMC disk, while those with larger values are closely distributed like a spheroidal component. Since GCs in both kinematic-structural components share similar ages and metallicities, we speculate with the possibility that their origins could have occurred through a fast collapse that formed halo and disk concurrently.

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.

scholarly journals Extraction of globular clusters members with Gaia DR2 astrometry

2019 ◽  
Author(s):  
Iván H Bustos Fierro ◽  
J H Calderón
Keyword(s):  
Spatial Distribution ◽  
Extraction Method ◽  
Globular Clusters ◽  
Clustering Algorithm ◽  
Proper Motions ◽  
Degree Of Contamination ◽  
The Mean ◽  
Using Data ◽  
Two Stages ◽  
Gaia Dr2

Abstract In this work we present a method to identify possible members of globular clusters using data from Gaia DR2. The method consists of two stages: the first one based on a clustering algorithm, and the second one based on the analysis of the projected spatial distribution of stars with different proper motions. In order to confirm that the clusters members extracted by the method correspond to actual globular clusters, the spatial distribution, the vector point diagram of the proper motions and the colour-magnitude diagrams are analysed. We apply the developed method to eight clusters: NGC 1261, NGC 3201, NGC 6139, NGC 6205, NGC 6362, NGC 6397, NGC 6712 and Palomar 13; we show the number of members extracted, the mean proper motions derived from them and finally we compare our results with other authors. In order to analyse the efficiency of the extraction method we perform an estimation of the completeness and the degree of contamination of the extracted members.

scholarly journals Characterizing dynamical stages of open clusters located in the Sagittarius spiral arm

2019 ◽  
Vol 488 (2) ◽  
pp. 1635-1651 ◽  
Author(s):  
M S Angelo ◽  
A E Piatti ◽  
W S Dias ◽  
F F S Maia
Keyword(s):  
Structural Parameters ◽  
Three Dimensional ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Mass Star ◽  
Proper Motions ◽  
Concentration Parameter ◽  
Low Mass ◽  
Gaia Dr2 ◽  
Spiral Arm

Abstract The study of dynamical properties of Galactic open clusters (OCs) is a fundamental prerequisite for the comprehension of their dissolution processes. In this work, we characterized 12 OCs, namely: Collinder 258, NGC 6756, Czernik 37, NGC 5381, Ruprecht 111, Ruprecht 102, NGC 6249, Basel 5, Ruprecht 97, Trumpler 25, ESO 129−SC32, and BH 150, projected against dense stellar fields. In order to do that, we employed Washington CT1 photometry and Gaia DR2 astrometry, combined with a decontamination algorithm applied to the three-dimensional astrometric space of proper motions and parallaxes. From the derived membership likelihoods, we built decontaminated colour–magnitude diagrams, while structural parameters were obtained from King profiles fitting. Our analysis revealed that they are relatively young OCs (log(t  yr−1) ∼7.3–8.6), placed along the Sagittarius spiral arm, and at different internal dynamical stages. We found that the half-light radius to Jacobi radius ratio, the concentration parameter and the age to relaxation time ratio describe satisfactorily their different stages of dynamical evolution. Those relative more dynamically evolved OCs have apparently experienced more important low-mass star loss.

Globular cluster tidal interactions and mergers in the Galactic disc

2019 ◽  
Vol 14 (S351) ◽  
pp. 442-446
Author(s):  
Alessandra Mastrobuono-Battisti ◽  
Sergey Khoperskov ◽  
Paola Di Matteo ◽  
Misha Haywood
Keyword(s):  
Globular Cluster ◽  
Iron Content ◽  
Globular Clusters ◽  
Dynamical Evolution ◽  
Stellar Populations ◽  
Cluster System ◽  
Galactic Disc ◽  
Tidal Interactions ◽  
Globular Cluster System ◽  
Shed Light

AbstractThe Galactic globular cluster system went and is still going through dynamical processes that require to be explored in detail. Here we illustrate how primordial massive globular clusters born in the Milky Way’s disc evolved by stripping material from each other or even merging very early during their lives. These processes might explain the puzzling presence of star-by-star spreads in iron content observed in massive globular clusters and should be taken into account when studying globular cluster stellar populations. In this context, we show how the direct comparison between the predictions provided by our direct N-body simulations and observations can shed light on the origin and chemo-dynamical evolution of globular clusters.

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 Detailed study of the Milky Way globular cluster Laevens 3

2019 ◽  
Vol 490 (2) ◽  
pp. 1498-1508
Author(s):  
Nicolas Longeard ◽  
Nicolas Martin ◽  
Rodrigo A Ibata ◽  
Michelle L M Collins ◽  
Benjamin P M Laevens ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Magnitude Diagram ◽  
Mass Segregation ◽  
Stellar Properties ◽  
Lyrae Stars ◽  
Gaia Dr2

ABSTRACT We present a photometric and spectroscopic study of the Milky Way satellite Laevens 3. Using MegaCam/Canada–France–Hawaii Telescope $g$ and $i$ photometry and Keck II/DEIMOS multi-object spectroscopy, we refine the structural and stellar properties of the system. The Laevens 3 colour–magnitude diagram shows that it is quite metal-poor, old ($13.0 \pm 1.0$ Gyr), and at a distance of $61.4 \pm 1.0$ kpc, partly based on two RR Lyrae stars. The system is faint ($M_V = -2.8^{+0.2}_{-0.3}$ mag) and compact ($r_h = 11.4 \pm 1.0$ pc). From the spectroscopy, we constrain the systemic metallicity (${\rm [Fe/H]}_\mathrm{spectro} = -1.8 \pm 0.1$ dex) but the metallicity and velocity dispersions are both unresolved. Using Gaia DR2, we infer a mean proper motion of $(\mu _\alpha ^*,\mu _\delta)=(0.51 \pm 0.28,-0.83 \pm 0.27)$ mas yr−1, which, combined with the system’s radial velocity ($\langle v_r\rangle = -70.2 \pm 0.5 {\rm \, km \,\, s^{-1}}$), translates into a halo orbit with a pericenter and apocenter of $40.7 ^{+5.6}_{-14.7}$ and $85.6^{+17.2}_{-5.9}$ kpc, respectively. Overall, Laevens 3 shares the typical properties of the Milky Way’s outer halo globular clusters. Furthermore, we find that this system shows signs of mass segregation that strengthens our conclusion that Laevens 3 is a globular cluster.

scholarly journals Gaia Data Release 2

2018 ◽  
Vol 616 ◽  
pp. A12 ◽  
Author(s):  
◽  
A. Helmi ◽  
F. van Leeuwen ◽  
P. J. McMillan ◽  
D. Massari ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Proper Motions ◽  
Single Plane ◽  
Dwarf Spheroidal Galaxies ◽  
Orbital Parameters ◽  
Data Release ◽  
Using Data

Context. Aims. The goal of this paper is to demonstrate the outstanding quality of the second data release of the Gaia mission and its power for constraining many different aspects of the dynamics of the satellites of the Milky Way. We focus here on determining the proper motions of 75 Galactic globular clusters, nine dwarf spheroidal galaxies, one ultra-faint system, and the Large and Small Magellanic Clouds. Methods. Using data extracted from the Gaia archive, we derived the proper motions and parallaxes for these systems, as well as their uncertainties. We demonstrate that the errors, statistical and systematic, are relatively well understood. We integrated the orbits of these objects in three different Galactic potentials, and characterised their properties. We present the derived proper motions, space velocities, and characteristic orbital parameters in various tables to facilitate their use by the astronomical community. Results. Our limited and straightforward analyses have allowed us for example to (i) determine absolute and very precise proper motions for globular clusters; (ii) detect clear rotation signatures in the proper motions of at least five globular clusters; (iii) show that the satellites of the Milky Way are all on high-inclination orbits, but that they do not share a single plane of motion; (iv) derive a lower limit for the mass of the Milky Way of 9.1-2.6+6.2 × 1011 M⊙ based on the assumption that the Leo I dwarf spheroidal is bound; (v) derive a rotation curve for the Large Magellanic Cloud based solely on proper motions that is competitive with line-of-sight velocity curves, now using many orders of magnitude more sources; and (vi) unveil the dynamical effect of the bar on the motions of stars in the Large Magellanic Cloud. Conclusions. All these results highlight the incredible power of the Gaia astrometric mission, and in particular of its second data release.

Investigation of the nearby open clusters with Gaia DR2 data

2019 ◽  
Vol 14 (S351) ◽  
pp. 502-506
Author(s):  
Anton F. Seleznev ◽  
Vladimir M. Danilov ◽  
Giovanni Carraro
Keyword(s):  
Three Dimensional ◽  
Open Clusters ◽  
Dimensional Structure ◽  
Proper Motions ◽  
Membership Probability ◽  
First Results ◽  
Alpha Persei ◽  
Mass Functions ◽  
Tidal Tails ◽  
Gaia Dr2

AbstractGaia DR2 catalog provides a unique possibility to study the three-dimensional structure and the three-dimensional velocity field of the nearby open clusters. We can either select stars with a maximum membership probability and the most accurate values for the proper motions, parallaxes, and the radial velocities, or study these clusters statistically using overwhelmingly large areas of sky of tens by tens degrees. The second approach allows us to reveal the extensive outer parts of the clusters - a corona and the tidal tails and to study the luminosity and mass functions of these clusters. We present the first results of the investigation of several nearby open clusters, including Pleiades, Alpha Persei, Ruprecht 147.

scholarly journals Open clusters as tracers on radial migration of the galactic disc

2020 ◽  
Vol 495 (3) ◽  
pp. 2673-2681 ◽  
Author(s):  
Y Q Chen ◽  
G Zhao
Keyword(s):  
Open Clusters ◽  
Important Process ◽  
Galactic Disc ◽  
Migration Distance ◽  
Radial Migration ◽  
Orbital Parameters ◽  
Migration Rates ◽  
Formation History ◽  
Gaia Dr2

ABSTRACT Radial migration is an important process in the Galactic disc. A few open clusters show some evidence on this mechanism but there is no systematic study. In this work, we investigate the role of radial migration on the Galactic disc based on a large sample of 146 open clusters with homogeneous metallicity and age from Netopil et al. and kinematics calculated from Gaia DR2. The birth site Rb, guiding radius Rg, and other orbital parameters are calculated, and the migration distance |Rg − Rb| is obtained, which is a combination of metallicity, kinematics, and age information. It is found that 44 per cent open clusters have |Rg − Rb| < 1 kpc, for which radial migration (churning) is not significant. Among the remaining 56 per cent open clusters with |Rg − Rb| > 1 kpc, young ones with t < 1.0 Gyr tend to migrate inward, while older clusters usually migrate outward. Different mechanisms of radial migration between young and old clusters are suggested based on their different migration rates, Galactic locations, and orbital parameters. For the old group, we propose a plausible way to estimate migration rate and obtain a reasonable value of $1.5 \pm 0.5 \,\rm {kpc\,Gyr}^{ -1}$ based on 10 intermediate-age clusters at the outer disc, where the existence of several special clusters implies its complicate formation history.

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