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

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.

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Gaia Data Release 2

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832698 ◽

2018 ◽

Vol 616 ◽

pp. A12 ◽

Cited By ~ 265

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.

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Extra-tidal features using Gaia DR2

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319007464 ◽

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.

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2061 ◽

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.

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