The elusive tidal tails of the Milky Way globular cluster NGC 7099

Piatti, Andrés E.; Carballo‐Bello, J. A.; Mora, Marcelo D.; Cenzano, C.; Navarrete, C.; Catelan, M.

doi:10.1051/0004-6361/202039012

Cited by 10 publications

(1 citation statement)

References 76 publications

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“…While the majority of studies have focused on the bright main bodies of GCs, DR2 has also led to dramatic improvements in our ability to study GC peripheries. Since the release of DR2, faint extra-tidal features have been discovered surrounding a number of clusters, such as E3 (Carballo-Bello et al 2020), NGC 362 (Carballo-Bello 2019), NGC 7099 (Sollima 2020;Piatti et al 2020), while a number of other clusters have had tidal extensions either recovered or found to extend further than previously known (e.g, Sollima 2020; Bonaca et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Detecting globular cluster tidal extensions with Bayesian inference – I. Analysis of ω Centauri with Gaia EDR3

Kuzma

Ferguson

Peñarrubia

2021

Monthly Notices of the Royal Astronomical Society

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The peripheral regions of globular clusters (GCs) are extremely challenging to study due to their low surface brightness nature and the dominance of Milky Way contaminant populations along their sightlines. We have developed a probabilistic approach to this problem through utilising a mixture model in spatial and proper motion space which separately models the cluster, extra-tidal and contaminant stellar populations. We demonstrate the efficacy of our method through application to Gaia EDR3 photometry and astrometry in the direction of NGC 5139 (ω Cen), a highly challenging target on account of its Galactic latitude (b ≈ 15○) and low proper motion contrast with the surrounding field. We recover the spectacular tidal extensions, spanning the 10○ on the sky explored here, seen in earlier work and quantify the star count profile and ellipticity of the system out to a cluster-centric radius of 4○. We show that both RR Lyrae and blue horizontal branch stars consistent with belonging to ω Cen are found in the tidal tails, and calculate that these extensions contain at least ≈0.1 per cent of the total stellar mass in the system. Our high probability members provide prime targets for future spectroscopic studies of ω Cen out to unprecedented radii.

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Section: Introductionmentioning

confidence: 99%

Detecting globular cluster tidal extensions with Bayesian inference – I. Analysis of ω Centauri with Gaia EDR3

Kuzma

Ferguson

Peñarrubia

2021

Monthly Notices of the Royal Astronomical Society

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The search for extratidal star candidates around Galactic globular clusters NGC 2808, NGC 6266, and NGC 6397 with Gaia DR2 astrometry

Kundu

Navarrete

Fernández-Trincado

et al. 2021

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Context. Extratidal stars are stellar bodies that end up outside the tidal radius of a cluster as a result of internal processes or external forces acting upon it. The presence and spatial distribution of these stars can give us insights into the past evolution of a cluster inside our Galaxy. Aims. Previous works suggest that globular clusters, when explored in detail, show evidence of extratidal stars. We aim to search for possible extratidal stars in the Galactic globular clusters NGC 6397, NGC 2808, and NGC 6266 using the photometry and proper motion measurements from Gaia DR2 database (Gaia Collaboration et al. 2018). Methods. The extratidal stars for the clusters were selected on the basis of: their distance from the cluster center, similarity in their proper motions to the cluster population, and their position on the color-magnitude diagram of the clusters. Each cluster was explored in an annulus disk from the tidal radius up to five times the tidal radii. The significance level of the number of selected extratidal stars was determined on the basis of the distribution of Milky Way stars according to the Besançon Galaxy model and Gaia data. To understand the observed extratidal features, the orbits of the clusters were also determined using GravPot16. Results. Finally, 120, 126, and 107 extratidal candidate stars were found lying outside the tidal radius of the globular clusters NGC 6397, NGC 2808, and NGC 6266, respectively. 70%, 25.4%, and 72.9% of the extratidal stars found are located outside the Jacobi radius of NGC 6397, NGC 2808, and NGC 6266, respectively. The spatial distribution of the extratidal stars belonging to NGC 6397 appears S-like, extending along the curved leading and trailing arms. NGC 2808 has an overdensity of stars in the trailing part of the cluster and NGC 6266 seems to have overdensities of extratidal stars in its eastern and northern sides. Conclusions. Proper motions and color-magnitude diagrams can be used to identify extratidal candidate stars around GCs. Nonetheless, depending on how different the kinematics and stellar populations of a cluster are compared to the Milky Way field, the fraction of contamination can be larger. All three clusters are found to have extratidal stars outside their tidal radii. For NGC 6397 and NGC 2808, these stars may be the result of a combined effect of the disc shocks and tidal disruptions. For NGC 6266, the distribution of extratidal stars is symmetrical around it, most likely indicating that the cluster has an extended stellar envelope.

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Astrophysical properties of newly discovered Magellanic Cloud star clusters

Piatti

2021

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New star cluster candidates projected toward the Large and Small Magellanic Clouds (LMC, SMC) have been recently discovered from relatively deep imaging surveys. Here, we conduct a sound analysis of 24 star cluster candidates located in the outer regions of the LMC and SMC using point spread function photometry produced by the Survey of the Magellanic Stellar History. With only one exception, the studied objects were shown to be genuine stellar aggregates. We drew our conclusions on their physical characteristics once their observed color-magnitude diagrams (CMDs) were statistically decontaminated by the presence of field stars. The resulting cleaned CMDs, for stars with assigned membership probabilities higher than 50%, were compared with synthetic CMDs generated for thousands of combinations of ages, distances, metallicities, star cluster masses, and binary fractions. The parameters of the best-matched synthetic CMDs obtained from a likelihood approach were adopted as the star cluster astrophysical properties. The present star cluster sample spans a wide range of distances, from those star clusters located in front of the LMC through those along the onset of the Magellanic Bridge up to those behind the SMC. Their ages reveal different formation episodes that took place over the course of galaxy formation and others as a consequence of interactions among galaxies. From their estimated metallicities and ages, we speculate on the possibility that relatively metal-deficient gaseous flows have existed between these galaxies during nearly the last one Gyr (log(age yr−1) ≈ 9.0), which facilitated the formation of young star clusters in the galaxy peripheries. Despide the LMC-SMC interactions, the studied star clusters are similar or more massive than their counterparts in the Milky Way, suggesting that tidal effects are relatively more important in our Galaxy.

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The elusive tidal tails of the Milky Way globular cluster NGC 7099

Cited by 10 publications

References 76 publications

Detecting globular cluster tidal extensions with Bayesian inference – I. Analysis of ω Centauri with Gaia EDR3

Detecting globular cluster tidal extensions with Bayesian inference – I. Analysis of ω Centauri with Gaia EDR3

The search for extratidal star candidates around Galactic globular clusters NGC 2808, NGC 6266, and NGC 6397 with Gaia DR2 astrometry

Astrophysical properties of newly discovered Magellanic Cloud star clusters

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