Eight more low luminosity globular clusters in the Sagittarius dwarf galaxy

Minniti, D.; Gómez, M.; Alonso-García, J.; Saito, R. K.; Garro, Elisa R.

doi:10.1051/0004-6361/202140714

Cited by 13 publications

(9 citation statements)

References 57 publications

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“…They used the VISTA Variables in the Via Lactea Extended (VVVX) survey, and confirmed based on their further analysis that 12 of them are bona fide members. Additionally, Minniti et al (2021a) later discovered 18 more GCs that might belong to the Sgr galaxy; 8 of them were confirmed as bona fide members. In both papers (hereafter M21, for simplicity), physical parameters such as reddening, extinction, and distance for each cluster were estimated.…”

Section: Introductionmentioning

confidence: 99%

Physical characterization of recently discovered globular clusters in the Sagittarius dwarf spheroidal galaxy

Garro

Minniti

Gómez

et al. 2021

A&A

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Context. Globular clusters (GCs) are important tools for rebuilding the accretion history of a galaxy. In particular, newly discovered GCs in the Sagittarius (Sgr) dwarf galaxy can be used as probes of the accretion event onto the Milky Way (MW). Aims. Our main aim is to characterize the GC system of the Sgr dwarf galaxy by measuring its main physical parameters. Methods. We built the optical and near-infrared color-magnitude diagrams for 21 new Sgr GCs using the VISTA Variables in the Via Lactea Extended Survey near-infrared database combined with the Gaia Early Data Release 3 optical database. We derived metallicities and ages for all targets using the isochrone-fitting method with PARSEC isochrones. We also used the relation between red giant branch slope and metallicity as an independent method to confirm our metallicity estimates. In addition, the total luminosities were calculated in the near-infrared and in the optical. We then constructed the metallicity distribution (MD), the globular cluster luminosity function (GCLF), and the age-metallicity relation for the Sgr GC system. Results. We find that there are 17 metal-rich GCs with −0.9 < [Fe/H]< − 0.3, plus 4 metal-poor GCs with −2.0 < [Fe/H]< − 1.1 in the new Sgr GC sample. The metallicity estimates using isochrones and red giant branch slopes agree well. Even though our age estimates are rough, we find that the metal-poor GCs are consistent with an old population with an average age of ∼13 Gyr, while the metal-rich GCs show a wider age range, between 6 − 8 Gyr and 10 − 13 Gyr. Additionally, we compare the MD and the GCLF for the Sgr GC system with those of the MW, M31, and Large Magellanic Cloud galaxies. Conclusions. We conclude that the majority of the metal-rich GCs are located within the main body of the Sgr galaxy. We confirm that the GCLF is not a universal distribution because the Sgr GCLF peaks at fainter luminosities (MV ≈ −5.5 mag) than the GCLFs of the MW, M31, and Large Magellanic Cloud. Moreover, the MD shows a double-peaked distribution, and we note that the metal-rich population looks like the MW bulge GCs. We compared our results with the literature and conclude that the Sgr progenitor could have been a reasonably large galaxy able to retain the supernovae ejecta, thus enriching its interstellar medium.

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Section: Introductionmentioning

confidence: 99%

Physical characterization of recently discovered globular clusters in the Sagittarius dwarf spheroidal galaxy

Garro

Minniti

Gómez

et al. 2021

A&A

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“…Four of the eight are old, metal-poor clusters; the other four are more metal-rich and younger, along the lines of the disk and halo clusters of the Milky Way (Searle & Zinn 1978). An additional 10-20 lower luminosity clusters are proposed members of Sgr (Minniti et al 2021). If the Milky Way is assembled out of systems similar to Sgr, then its one cluster (M54) in a dark halo of the nine luminous clusters somewhat weakly bolsters the idea that roughly 10% of disk galaxy clusters retain pre-galactic dark matter halos.…”

Section: Discussionmentioning

confidence: 99%

The Dark Matter Halo of M54

Carlberg

Grillmair

2022

ApJ

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M54 is a prototype for a globular cluster embedded in a dark matter halo. Gaia Early Data Release 3 photometry and proper motions separate the old, metal-poor stars from the more metal-rich and younger dwarf galaxy stars. The metal-poor stars dominate the inner 50 pc, with a velocity dispersion profile that declines to a minimum around 30 pc then rises back to nearly the central velocity dispersion, as expected for a globular cluster at the center of a cold dark matter (CDM) cosmology dark matter halo. The Jeans equation mass analysis of the three separate stellar populations gives consistent masses that rise approximately linearly with radius to 1 kpc. These data are compatible with an infalling CDM dark matter halo reduced to ≃3 × 108 M ⊙ at the 50 kpc apocenter 2.3 Gyr ago, with a central globular cluster surrounded by the remnant of a dwarf galaxy. Tides gradually remove material beyond 1 kpc but have little effect on the stars and dark matter within 300 pc of the center. M54 appears to be a “transitional” system between globular clusters with and without local dark halos whose evolution within the galaxy depends on the time of accretion and orbital pericenter.

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“…Four of the eight are old, metal poor clusters, the other 4 are more metal rich and younger, along the lines of the disk and halo clusters of the Milky Way (Searle & Zinn 1978). An additional 10-20 lower luminosity clusters are proposed members of Sagittarius (Minniti et al 2021). If the Milky Way is assembled out of systems similar to Sagittarius, then its one cluster (M54) in a dark halo of the nine luminous clusters somewhat weakly bolsters the idea that roughly 10% of disk galaxy clusters retaining pre-galactic dark matter halos.…”

Section: Discussionmentioning

confidence: 99%

The Dark Matter Halo of M54

Carlberg,

Grillmair

2022

Preprint

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M54 is a prototype of a globular cluster embedded in a dark matter halo. Gaia EDR3 photometry and proper motions separate the old, metal-poor stars from the more metal rich and younger dwarf galaxy stars. The metal poor stars dominate the inner 50 pc, with a velocity dispersion profile that declines to a minimum around 30 pc then rises back to nearly the central velocity dispersion, as expected for a globular cluster at the center of a dark matter halo. The Jeans analysis of the three separate stellar populations give consistent masses that rise approximately linearly with radius to 1 kpc, implying a small core or cuspy halo. These data are compatible with an infalling CDM dark matter halo reduced to 3 × 10 8 M at the 50 kpc apocenter 2.3 Gyr ago, with a central globular cluster surrounded by the remnant of a dwarf galaxy. Tides gradually remove material beyond 1 kpc but have little effect on the stars and dark matter within 300 pc of the center. M54 appears to be a "transitional" system between globular clusters with and without local dark halos, whose evolution within the galaxy depends sensitively on the time of accretion and orbital pericenter.

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Eight more low luminosity globular clusters in the Sagittarius dwarf galaxy

Cited by 13 publications

References 57 publications

Physical characterization of recently discovered globular clusters in the Sagittarius dwarf spheroidal galaxy

Physical characterization of recently discovered globular clusters in the Sagittarius dwarf spheroidal galaxy

The Dark Matter Halo of M54

The Dark Matter Halo of M54

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