Is there a fundamental upper limit to the mass of a star cluster?

Norris, Mark A.; Ven, Glenn van de; Kannappan, Sheila J.; Schinnerer, E.; Leaman, Ryan

doi:10.1093/mnras/stz2096

Cited by 24 publications

(19 citation statements)

References 133 publications

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“…This is roughly the mass that is believed to be the upper mass limit for the true old star cluster population (e.g. Norris et al 2019) which is consistent with our finding that at M > 1 × 10 7 M simulated stripped nuclei have near-solar metallicities, consistent with observed UCDs.…”

Section: Metallicitysupporting

confidence: 91%

Testing the tidal stripping scenario of ultra-compact dwarf galaxy formation by using internal properties

Mayes,

Drinkwater,

Pfeffer

et al. 2021

Preprint

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We use the hydrodynamical EAGLE simulation to test if ultra-compact dwarf galaxies (UCDs) can form by tidal stripping by predicting the ages and metallicities of tidally stripped galaxy nuclei in massive galaxy clusters, and compare these results to compiled observations of age and metallicities of observed UCDs. We further calculate the colours of our sample of simulated stripped nuclei using SSP models and compare these colours to observations of UCDs in the Virgo cluster. We find that the ages of observed UCDs are consistent with simulated stripped nuclei, with both groups of objects having a mean age > 9 Gyr. Both stripped nuclei and UCDs follow a similar mass-metallicity relationship, and the metallicities of observed UCDs are consistent with those of simulated stripped nuclei for objects with M > 10 7 M . The colours of observed UCDs are also consistent with our simulated stripped nuclei, for objects with M > 10 7 M , with more massive objects being redder. We find that the colours of stripped nuclei exhibit a bimodal red and blue distribution that can be explained by the dependency of colour on age and metallicity, and by the mass-colour relation. We additionally find that our low mass stripped nuclei sample is consistent with the colour of blue globular clusters. We conclude that the internal properties of simulated nuclei support the tidal stripping model of UCD formation.

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Section: Metallicitysupporting

confidence: 91%

Testing the tidal stripping scenario of ultra-compact dwarf galaxy formation by using internal properties

Mayes,

Drinkwater,

Pfeffer

et al. 2021

Preprint

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“…We next tested the influence of M cl, max , the mass of the most massive GC that ever formed. The posterior values returned by the default model for M cl,max are well within the observed values seen in the Milky Way and Local Volume, and even merging systems (Renaud 2018), but the upper limit to the prior of M cl, max = 7.6 × 10 7 M (Norris et al 2019a) is reached for some of the highest f in, NSC systems. Increasing this limit by one order of magnitude to ∼ 7 × 10 8 ('M cl, max < 10 8.8 ' model) can reduce the in situ fractions in these galaxies by ∼ 10 percent.…”

Section: Dependence On Parameter Setupssupporting

confidence: 69%

“…The most massive cluster that ever formed, M cl, max , shows a positive correlation with f in, NSC and reaches the upper limit of the prior for galaxies with high in situ fractions. Studies of molecular cloud formation and statistical arguments on GC populations (Reina-Campos & Kruijssen 2017; Norris et al 2019b) suggest that this value is unlikely to significantly exceed the range of our default prior of 7.6 × 10 7 M ; however, we discuss further how the choice of this prior affects the results in Sect. 5.1.…”

Section: Trends With Model Parametersmentioning

confidence: 85%

Disentangling the formation mechanisms of nuclear star clusters

Fahrion,

Leaman,

Lyubenova

et al. 2021

Preprint

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Nuclear star clusters (NSCs) are massive star clusters found ubiquitously in the centres of galaxies, from the dwarf regime to massive ellipticals and spirals. The fraction of nucleated galaxies is as high as > 90 % at M gal ∼ 10 9 M . However, how NSC formation mechanisms work in different regimes and what determines galaxy nucleation is still unclear. The dissipationless accretion of infalling globular clusters (GCs) and the in situ formation of stars directly at the galactic centre likely operate to grow NSCs in most galaxies; however, their efficiency has been difficult to assess observationally. Here, we provide, for the first time, a quantitative determination of the relative strength of these processes in the build-up of individual NSCs. Using a semi-analytical model of NSC formation based on the orbital evolution of inspiraling GCs, together with observed NSC and GC system properties, we derived the mass fraction of in situ born stars f in, NSC for 119 galaxies with masses from 3 × 10 7 to 3 × 10 11 M , in the Local Volume, the Fornax, and Virgo galaxy clusters. Our analysis reveals that the NSC mass, as well as the ratio of NSC to the total GC system mass, are strong indicators of the dominant NSC formation channel, and not the total galaxy stellar mass as previously suggested. More massive NSCs formed predominantly via the in situ formation of stars ( f in, NSC ∼ 0.9), while the lower-mass NSCs are expected to have formed predominantly through the merger of GCs ( f in, NSC ∼ 0.2). The results of this simple model are in agreement with recent independent estimates of the dominant NSC formation channel from recent stellar population analysis.

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“…A large number of stripped nuclei are expected around massive galaxies and in galaxy clusters due to the hierarchical nature of galaxy merging. Simulations are consistent with most of the higher mass GCs ( 10 7 M ) in clusters being stripped galaxy nuclei (Pfeffer et al 2016;Mayes et al 2021;Norris et al 2019). They also suggest that lower mass galaxies will contain lower mass stripped nuclei, and that the Milky Way may contain 2-6 stripped nuclei (Pfeffer et al 2014;Kruijssen et al 2019).…”

Section: Introductionsupporting

confidence: 60%

A population of luminous globular clusters and stripped nuclei with elevated mass to light ratios around NGC 5128

Dumont,

Seth,

Strader

et al. 2021

Preprint

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The dense central regions of tidally disrupted galaxies can survive as ultra-compact dwarfs (UCDs) that hide among the luminous globular clusters (GCs) in the halo of massive galaxies. An exciting confirmation of this model is the detection of overmassive black holes in the centers of some UCDs, which also lead to elevated dynamical mass-to-light ratios (M/L dyn ). Here we present new high-resolution spectroscopic observations of 321 luminous GC candidates in the massive galaxy NGC 5128/Centaurus A. Using these data we confirm 27 new luminous GCs, and measure velocity dispersions for 57 luminous GCs (with g-band luminosities between 2.5 × 10 5 and 2.5 × 10 7 L ), of which 48 have no previous reliable measurements. Combining these data with size measurements from Gaia, we determine the M/L dyn for all 57 luminous GCs. We see a clear bimodality in the M/L dyn distribution, with a population of normal GCs with mean M/L dyn = 1.51 ± 0.31, and a second population of ∼20 GCs with elevated mean M/L dyn = 2.68 ± 0.22. We show that black holes with masses ∼ 4-18% of the luminous GCs can explain the elevated mass-to-light ratios. Hence, it is plausible that the NGC 5128 sources with elevated M/L dyn are mostly stripped galaxy nuclei that contain massive central black holes, though future high spatial resolution observations are necessary to confirm this hypothesis for individual sources. We also present a detailed discussion of an extreme outlier, VHH81-01, one of the largest and most massive GC in NGC 5128, making it an exceptionally strong candidate to be a tidally stripped nucleus.

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Is there a fundamental upper limit to the mass of a star cluster?

Cited by 24 publications

References 133 publications

Testing the tidal stripping scenario of ultra-compact dwarf galaxy formation by using internal properties

Testing the tidal stripping scenario of ultra-compact dwarf galaxy formation by using internal properties

Disentangling the formation mechanisms of nuclear star clusters

A population of luminous globular clusters and stripped nuclei with elevated mass to light ratios around NGC 5128

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