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

Kundu, Richa; Navarrete, C.; Fernández-Trincado, J. G.; Minniti, D.; Singh, Harinder P.; Sbordone, L.; Piatti, Andrés E.; Reylé, C.

doi:10.1051/0004-6361/202038720

Cited by 15 publications

(8 citation statements)

References 87 publications

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“…The bulge of the Milky Way (MW) is populated by a large collection ( 40) of ancient globular clusters (GCs) within ∼3.5 kpc of the Galactic center (for a detailed description, see a review by Bica et al 2016; Barbuy et al 2018;Pérez-Villegas et al 2020), which serves as the fossil record of its evolutionary history (Recio-Blanco et al 2017;Minniti et al 2018aMinniti et al , 2021Kundu et al 2019Kundu et al , 2021Fernández-Trincado et al 2019a,b, 2020a,b,c,d, 2021a.…”

Section: Introductionmentioning

confidence: 99%

CAPOS: The bulge Cluster APOgee Survey

Romero-Colmenares¹,

Fernández-Trincado²,

Geisler³

et al. 2021

A&A

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We present results from a study of 15 red giant members of the intermediate-metallicity globular cluster (GC) FSR 1758 using high-resolution, near-infrared spectra collected with the Apache Point Observatory Galactic Evolution Experiment II survey (APOGEE-2) that were obtained as part of CAPOS (the bulge Cluster APOgee Survey). Since its very recent discovery as a massive GC in the bulge region, evoking the name Sequoia, this has been an intriguing object with a highly debated origin, and initially led to the suggestion of a purported progenitor dwarf galaxy of the same name. In this work, we use new spectroscopic and astrometric data to provide additional clues as to the nature of FSR 1758. Our study confirms the GC nature of FSR 1758, and as such we report the existence of the characteristic N-C anticorrelation and Al-N correlation for the first time. We thereby reveal the existence of the multiple-population phenomenon, similar to that observed in virtually all GCs. Furthermore, the presence of a population with strongly enriched aluminum makes it unlikely that FSR 1758 is the remnant nucleus of a dwarf galaxy because Al-enhanced stars are uncommon in dwarf galaxies. We find that FSR 1758 is slightly more metal rich than previously reported in the literature; this source has a mean metallicity [Fe/H] between −1.43 to −1.36, depending on the adopted atmospheric parameters and a scatter within observational error, again pointing to its GC nature. Overall, the α-enrichment (≳ + 0.3 dex), Fe-peak (Fe, Ni), light (C, N), and odd-Z (Al) elements follow the trend of intermediate-metallicity GCs. Isochrone fitting in the Gaia bands yields an estimated age of ∼11.6 Gyr. We used the exquisite kinematic data, including our CAPOS radial velocities and Gaia eDR3 proper motions, to constrain the N-body density profile of FSR 1758, and found that it is as massive (∼2.9 ± 0.6 × 105 M⊙) as NGC 6752. We confirm a retrograde and eccentric orbit for FSR 1758. A new examination of its dynamical properties with the GravPot16 model favors an association with the Gaia-Enceladus-Sausage accretion event. Thus, paradoxically, the cluster that gave rise to the name of the Sequoia dwarf galaxy does not appear to belong to this specific merging event.

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Section: Introductionmentioning

confidence: 99%

CAPOS: The bulge Cluster APOgee Survey

Romero-Colmenares¹,

Fernández-Trincado²,

Geisler³

et al. 2021

A&A

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“…In order to select the extra-tidal candidates of each cluster, we select the stars with similar PMs and CMDs as the cluster stars inside one r t , similar to the criteria used in Kundu et al (2019bKundu et al ( ,a, 2021. Stars lying between r t to 5r t from the cluster centre were considered as the extra-tidal candidates in this study.…”

Section: ) Visibility_periods_used > 10mentioning

confidence: 99%

Extra-tidal star candidates in globular clusters of the Sagittarius dwarf spheroidal galaxy

Kundu

Navarrete

Sbordone

et al. 2022

A&A

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Context. Globular clusters (GCs) associated with the Sagittarius dwarf spheroidal galaxy (Sgr dSph) have evolved under the gravitational potential of both Sgr dSph and the Milky Way. The effects of these potentials are most pronounced in the extra-tidal regions as compared to the central regions of the GCs. Aims. We aim to study the extra-tidal regions of the GCs that are possibly associated with Sgr dSph, namely Arp 2, Terzan 8, NGC 5634, NGC 6284, Terzan 7, NGC 2419, NGC 4147, M 54 and Pal 12, using data from the Gaia early data release 3. Methods. We selected the extra-tidal candidates based on their angular distances from the cluster centre in the RA-Dec plane, proper motions of the clusters and the individual extra-tidal star candidates, and their positions on the colour-magnitude diagrams of the clusters.Results. We found extra-tidal candidates for the nine studied GCs. For eight of them, the surface density of candidate extra-tidal stars in the vicinity of the clusters is in significant excess with respect to more distant surrounding fields. No extended extra-tidal features beyond 5 tidal radii were detected for any of the clusters. Conclusions. We publish a list of the most probable extra-tidal candidates that we determined using Gaia astrometric and photometric data. Our analysis shows that the clusters that are associated with Sgr dSph are more likely affected by the gravitational potential of the Sgr, as the distribution of extra-tidal stars is elongated in the same direction as the local stream. NGC 4147 is the only exception. We found some high-probability candidate extra-tidal stars in several of the analysed clusters. We failed to detect any coherent large-scale tidal tail around them.

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“…• NGC 6397: This is one of the closest globular clusters, and is not in the compilation of PCB20. Ibata et al (2021) find evidence for a long tidal tail ≈ 25 • in length, using Gaia EDR3 (see also Kundu et al 2021). While Boldrini & Vitral (2021) are unable to reproduce this detection, we elect to classify this cluster 'T' based on the generally robust success of the Ibata et al (2019bIbata et al ( , 2021 algorithm.…”

Section: A2 Classified Clustersmentioning

confidence: 99%

A search for stellar structures around nine outer halo globular clusters in the Milky Way

Zhang,

Mackey,

Da Costa

2021

Preprint

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We use deep imaging from the Dark Energy Camera to explore the peripheral regions of nine globular clusters in the outer halo of the Milky Way. Apart from Whiting 1 and NGC 7492, which are projected against the Sagittarius stream, we see no evidence for adjacent stellar populations to indicate any of these clusters is associated with coherent tidal debris from a destroyed host dwarf. We also find no evidence for tidal tails around any of the clusters in our sample; however, both NGC 1904 and 6981 appear to possess outer envelopes. Motivated by a slew of recent Gaia-based discoveries, we compile a sample of clusters with robust detections of extra-tidal structure, and search for correlations with orbital properties. While we observe that clusters with tidal tails are typically on moderately or very eccentric orbits that are highly inclined to the Galactic plane and often retrograde, these are neither necessary nor sufficient conditions for the formation of extra-tidal structure. That many objects with tidal tails appear to be accreted leads us to speculate that this lack of consistency may stem from the inhomogeneous dynamical history of the Milky Way globular cluster system. Finally, we note that clusters with prominent stellar envelopes detected in ground-based imaging (such as NGC 1851 and 7089) are now all known from Gaia to possess long tidal tails -experimental confirmation that the presence of an extended envelope is indicative of tidal erosion.

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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

Cited by 15 publications

References 87 publications

CAPOS: The bulge Cluster APOgee Survey

CAPOS: The bulge Cluster APOgee Survey

Extra-tidal star candidates in globular clusters of the Sagittarius dwarf spheroidal galaxy

A search for stellar structures around nine outer halo globular clusters in the Milky Way

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