Detailed Chemical Composition and Orbit of the Newly Discovered Globular Cluster FSR 1758: Implications for the Accretion of the Sequoia Dwarf Galaxy onto the Milky Way*

Villanova, S.; Monaco, L.; Geisler, Doug; O’Connell, Julia; Minniti, D.; Assmann, P.; Barbá, R. H.

doi:10.3847/1538-4357/ab3722

Cited by 35 publications

(60 citation statements)

References 93 publications

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“…While we downloaded the available data from the respective repositories for 2MASS and Gaia DR2, we used a preliminary version of the point spread function (PSF) photometry for VVVX, which we are developing for its whole footprint based on Alonso-García et al (2018) VVV PSF photometry. This VVVX PSF photometry was already used by Barbá et al (2019) for the discovery and characterisation of FSR-1758, a giant metalpoor retrograde GC (Villanova et al 2019), and by Minniti et al (2018) for the discovery of extra tidal RR Lyrae stars in the metal-poor bulge GC NGC 6266 (M 62). For our analysis, we put the VVVX PSF photometry of our region of interest in the 2MASS JHK s photometric system.…”

Section: Physical Characterisation Of the New Gc Garro01mentioning

confidence: 99%

VVVX-Gaia discovery of a low luminosity globular cluster in the Milky Way disk

Garro

Minniti

Gómez

et al. 2020

A&A

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Context. Milky Way globular clusters (GCs) are difficult to identify at low Galactic latitudes because of high differential extinction and heavy star crowding. The new deep near-infrared (IR) images and photometry from the VISTA Variables in the Via Láctea Extended Survey (VVVX) allow us to chart previously unexplored regions. Aims. Our long term aim is to complete the census of Milky Way GCs. The immediate goals are to estimate the astrophysical parameters for the newly discovered GC candidates, measuring their reddenings, extinctions, distances, total luminosities, proper motions, sizes, metallicities, and ages. Methods. We used the near-IR VVVX survey database, in combination with the optical photometry and proper motions (PMs) from Gaia Data Release 2 (DR2), and with the Two Micron All Sky Survey photometry to search for and characterise new GCs within the southern Galactic plane (|b| < 5°). Results. We report the detection of a heretofore unknown Galactic GC at RA = 14:09:00.0; Dec = −65:37:12 (J2000) corresponding to l = 310.828 deg; and b = −3.944 deg in galactic coordinates. We calculate a reddening of E(J − Ks) = (0.3 ± 0.03) mag and an extinction of AKs = (0.15 ± 0.01) mag for this new GC. Its distance modulus and corresponding distance were measured as (m − M) = (15.93 ± 0.03) mag and D = (15.5 ± 1.0) kpc, respectively. We also estimate the metallicity and age by comparison with known GCs and by fitting PARSEC and Dartmouth isochrones, finding [Fe/H] = ( − 0.70 ± 0.2) dex and t = (11.0 ± 1.0) Gyr. The mean GC PMs from Gaia DR2 are μα* = ( − 4.68 ± 0.47) mas yr−1 and μδ = ( − 1.34 ± 0.45) mas yr−1. The total luminosity of our cluster is estimated to be MKs = ( − 7.76 ± 0.5) mag. The core and tidal radii from the radial density profile are rc ∼ 2.1′ (4.6 pc) and rt = 6.5′ (14.6 pc) at the cluster distance. Conclusions. We have found a new low luminosity, old and metal-rich GC, situated in the far side of the Galactic disk at RG = 11.2 kpc from the Galactic centre and at z = 1.0 kpc below the plane. Interestingly, the location, metallicity, and age of this GC are coincident with the Monoceros ring structure.

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Section: Physical Characterisation Of the New Gc Garro01mentioning

confidence: 99%

VVVX-Gaia discovery of a low luminosity globular cluster in the Milky Way disk

Garro

Minniti

Gómez

et al. 2020

A&A

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“…It might equally be an in-situ halo GCs, if we limit ourselves to orbital parameter analysis. According to the detailed chemical abundance analysis done by Villanova et al (2019), FSR 1758 is found to contain similar trend in α elements and Na-O anti-correlation for metal-poor halo GCs. This, in our opinion, lends more support to a more conservative scenario in which FSR 1758 is most probably a halo GC formed inside the Milky Way .…”

Section: Discussionmentioning

confidence: 91%

The origin of globular cluster FSR 1758

Yeh

Carraro

Корчагин

et al. 2020

A&A

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Context. Globular clusters in the Milky Way are thought to have either an in situ origin, or to have been deposited in the Galaxy by past accretion events, like the spectacular Sagittarius dwarf galaxy merger. Aims. We aim to probe the origin of the recently discovered globular cluster FSR 1758, often associated with some past merger event, and which happens to be projected toward the Galactic bulge, by a detailed study of its Galactic orbit, and to assign it to the most suitable Galactic component. Methods. We employ three different analytical time-independent potential models to calculate the orbit of the cluster by using the Gauss Radau spacings integration method. In addition, a time-dependent bar potential model is added to account for the influence of the Galactic bar. We run a large suite of simulations to account for the uncertainties in the initial conditions, in a Montecarlo fashion. Results. We confirm previous indications that the globular cluster FSR 1758 possesses a retrograde orbits with high eccentricity. The comparative analysis of the orbital parameters of star clusters in the Milky Way, in tandem with recent metallicity estimates, allows us to conclude that FSR1758 is indeed a Galactic bulge intruder. The cluster can therefore be considered an old metal poor halo globular cluster formed in situ and which is passing right now in the bulge region. Its properties, however, can be roughly accounted for also assuming that the cluster is part of some stream of extra-Galactic origin. Conclusions. We conclude that assessing the origin, either Galactic or extra-galactic, of globular clusters is surely a tantalising task. In any case, by using an Occam's razor argument, we tend to prefer an in situ origin for FSR 1758.

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“…It has been shown that the most Na-poor limit in dwarf galaxies is lower than the Na abundance of Milky Way field stars, with some exceptions (Colucci et al 2012;Ishigaki et al 2014;Battaglia et al 2017;Villanova et al 2019;Salgado et al 2019;Matsuno et al 2019;Aguado et al 2020). Therefore, first generation stars of globular clusters formed in accreted dwarf galaxies should mostly have Na abundances lower than their counterparts of globular clusters that formed in situ, which explains the range of 1G values seen in Fig.…”

Section: Analysis and Discussionmentioning

confidence: 99%

Different sodium enhancements among multiple populations of Milky Way globular clusters

Piatti

2020

A&A

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We searched for clues to understand the different Na abundances measured in first and second generation stars of ancient Milky Way globular clusters. For that purpose, from the recent literature, we gathered the aforementioned Na abundances, orbital parameters, and structural and internal dynamical properties and ages in a homogeneous scale of 28 globular clusters. We found that the intra-cluster Na enrichment, which is measured by the difference of Na abundances between first and second generation stars, exhibits a trend as a function of the Na abundances of first generation stars, in the sense that the more Na-poor the first generation stars are, the larger the Na enrichment is. By using the inclinations of the globular clusters’ orbits, the analyzed Na enrichments also hinted at a boundary at ∼0.3 dex to differentiate globular clusters with an accreted or in situ origin, the accreted globular clusters having larger Na enrichments. Because relatively larger intra-cluster Na enhancements are seen in accreted globular clusters and small Na enhancements are observed in globular clusters formed in situ, although not exclusively, we speculate that the amplitude of the Na enrichment may be linked with the building block paradigm. Globular clusters at the time of formation of first and second generation stars would seem to keep a memory of this hierarchical galaxy formation process.

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Detailed Chemical Composition and Orbit of the Newly Discovered Globular Cluster FSR 1758: Implications for the Accretion of the Sequoia Dwarf Galaxy onto the Milky Way*

Cited by 35 publications

References 93 publications

VVVX-Gaia discovery of a low luminosity globular cluster in the Milky Way disk

VVVX-Gaia discovery of a low luminosity globular cluster in the Milky Way disk

The origin of globular cluster FSR 1758

Different sodium enhancements among multiple populations of Milky Way globular clusters

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