A new low-luminosity globular cluster discovered in the Milky Way with the VVVX survey

Garro, Elisa R.; Minniti, D.; Gómez, M.; Fernández-Trincado, J. G.; Alonso-García, J.; Hempel, M.; Bacigalupo, R. Zelada

doi:10.1051/0004-6361/202243342

Cited by 11 publications

(1 citation statement)

References 62 publications

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“…The different stellar populations in the bulge exhibit different kinematics. Proper motions are thus a valuable tool for distinguishing bulge and disc stars and for identifying structures such as streams or globular clusters (Horta et al 2021;Kader et al 2022;Garro et al 2022). They can also be used to characterise structures such as the nuclear star cluster or the nuclear stellar disc Shahzamanian et al 2022;Nogueras-Lara 2022).…”

Section: Introductionmentioning

confidence: 99%

Astrometry in crowded fields towards the Galactic bulge

Luna¹,

Marchetti²,

Rejkuba³

et al. 2023

A&A

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Context. The astrometry towards the Galactic bulge is hampered by high stellar crowding and patchy extinction. This effect is particularly severe for optical surveys such as the European Space Agency satellite Gala. Aims. In this study, we assess the consistency of proper motion measurements between optical (Gaia DR3) and near-infrared (VIRAC2) catalogues in comparison with proper motions measured with the Hubble Space Telescope (HST) observations in several crowded fields towards the Galactic bulge and in Galactic globular clusters. Methods. Assuming that the proper motion measurements are well characterised, the uncertainty-normalised proper motion differences between pairs of catalogues are expected to follow a normal distribution. A deviation from a normal distribution defines the inflation factor r. By multiplying the proper motion uncertainties with the appropriate inflation factor values, the Gaia (VIRAC2) proper motion measurements are brought into a 1σ agreement with the HST proper motions. Results. The inflation factor (r) depends on stellar surface density. For the brightest stars in our sample (G < 18), the dependence on G-band magnitude is strong, corresponding to the most precise Gaia DR3 proper motions. We used the number of observed Gaia DR3 sources as a proxy for the stellar surface density. Assuming that the HST proper motion measurements are well determined and free from systematic errors, we find that Gaia DR3 proper motion uncertainties are better characterised, having r < 1.5 in fields with a stellar number density with fewer than 200 Gaia DR3 sources per arcmin2, and are underestimated by up to a factor of 4 in fields with stellar densities higher than 300 sources per arcmin2. For the most crowded fields in VIRAC2, the proper motion uncertainties are underestimated by a factor of 1.1 up to 1.5, with a dependence on J-band magnitude. In all fields, the brighter sources have the higher r value. At the faint end (G > 19), the inflation factor is close to 1, meaning that the proper motions already fully agree with the HST measurements within 1σ. Conclusions. In the crowded fields common to both catalogues, VIRAC2 proper motions agree with HST proper motions and do not need an inflation factor for their uncertainties. Because of the depth and completeness of VIRAC2 in these fields, it is an ideal complement to Gaia DR3 for proper motion studies towards the Galactic bulge.

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Section: Introductionmentioning

confidence: 99%

Astrometry in crowded fields towards the Galactic bulge

Luna¹,

Marchetti²,

Rejkuba³

et al. 2023

A&A

View full text Add to dashboard Cite

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Statistical determination of the distance to the Galactic Centre and the outset of the Milky Way old bulge: astrophysical conclusions

Griv,

Jiang,

Majaess

et al. 2023

Astrophys Space Sci

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Globular clusters in the Galactic center region: Expected behavior within the infall and merger scenario

Navarro¹,

Capuzzo-Dolcetta²,

Arca-Sedda³

et al. 2023

A&A

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In this work, we reexamine the infall and merger scenario of massive clusters in the Milky Way’s potential well as a plausible Milky Way formation mechanism. We aim to understand how the stars of the merging clusters are redistributed during and after the merger process. We used, for the first time, high-resolution simulations with concentrated in the 300 pc around the Galactic center. We adopted simulations developed in the framework of the Modelling the Evolution of Galactic Nuclei (MEGaN) project. We compared the evolution of representative clusters in the mass and concentration basis in the vicinity of a supermassive black hole. We used the spatial distribution, density profile, and the 50% Lagrange radius (half mass radius) as indicators along the complete simulation to study the evolutionary shape in physical and velocity space and the final fate of these representative clusters. We find that the least massive clusters are quickly (< 10 Myr) destroyed. On the other hand, the most massive clusters have a long evolution, showing variations in the morphology, especially after each passage close to the supermassive black hole. The deformation of the clusters depends on the concentration, with general deformations for the least concentrated clusters and outer strains for the more concentrated ones. At the end of the simulation, a dense concentration of stars belonging to the clusters was formed. The particles that belong to the most massive and most concentrated clusters are concentrated in the innermost regions, meaning that the most massive and concentrated clusters contribute a more significant fraction of particles to the final concentration. This finding suggests that the population of stars of the nuclear star cluster formed through this mechanism comes from massive clusters rather than low-mass globular clusters.

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A new low-luminosity globular cluster discovered in the Milky Way with the VVVX survey

Cited by 11 publications

References 62 publications

Astrometry in crowded fields towards the Galactic bulge

Astrometry in crowded fields towards the Galactic bulge

Statistical determination of the distance to the Galactic Centre and the outset of the Milky Way old bulge: astrophysical conclusions

Globular clusters in the Galactic center region: Expected behavior within the infall and merger scenario

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