Globular Cluster Systems and Galaxy Formation

Beasley, Michael A.

doi:10.1007/978-3-030-38509-5_9

Cited by 38 publications

(19 citation statements)

References 137 publications

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“…This is not surprising as most massive galaxies show two populations of GCs that differ in their metallicity with a metal-rich population that was formed in-situ in the host, and a metal-poor population stemming from accreted dwarf galaxies (e.g. Harris 1991;Peng et al 2006;Lamers et al 2017;Beasley 2020;Fahrion et al 2020a,b).…”

Section: Metallicity Distributionsmentioning

confidence: 99%

Diversity of nuclear star cluster formation mechanisms revealed by their star formation histories

Fahrion,

Lyubenova,

van de Ven

et al. 2021

Preprint

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Nuclear star clusters (NSCs) are the densest stellar systems in the Universe and are found in the centres of all types of galaxies. They are thought to form via mergers of star clusters such as ancient globular clusters (GCs) that spiral to the centre as a result of dynamical friction or through in-situ star formation directly at the galaxy centre. There is evidence that both paths occur, but the relative contribution of either channel and their correlation with galaxy properties are not yet constrained observationally. We aim to derive the dominant NSC formation channel for a sample of 25 nucleated galaxies, mostly in the Fornax galaxy cluster, with stellar masses between M gal ∼ 10 8 and 10 10.5 M and NSC masses between M NSC ∼ 10 5 and 10 8.5 M . Using Multi-Unit Spectroscopic Explorer (MUSE) data from the Fornax 3D survey and the ESO archive, we derive star formation histories, mean ages and metallicities of NSCs, and compare them to the host galaxies. In many low-mass galaxies, the NSCs are significantly more metal-poor than their hosts with properties similar to GCs. In contrast, in the massive galaxies, we find diverse star formation histories and cases of ongoing or recent in-situ star formation. Massive NSCs (> 10 7 M ) occupy a different region in the mass-metallicity diagram than lower mass NSCs and GCs, indicating a different enrichment history. We find a clear transition of the dominant NSC formation channel with both galaxy and NSC mass. We hypothesise that while GC-accretion forms the NSCs of the dwarf galaxies, central star formation is responsible for the efficient mass build up in the most massive NSCs in our sample. At intermediate masses, both channels can contribute. The transition between these formation channels seems to occur at galaxy masses M gal ∼ 10 9 M and NSC masses M NSC ∼ 10 7 M .

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Section: Metallicity Distributionsmentioning

confidence: 99%

Diversity of nuclear star cluster formation mechanisms revealed by their star formation histories

Fahrion,

Lyubenova,

van de Ven

et al. 2021

Preprint

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“…Globular clusters (GCs) -old massive star clusters formed in the early stages of galaxy assembly -are generally found in all galaxies except the smallest dwarfs (Harris 2010;Forbes et al 2018;Beasley 2020). For galaxies with GC populations, empirical evidence suggests that the total mass in GCs (M gcs ) is nearly proportional to the host galaxy's total halo mass (M h ) rather than its total stellar mass M (e.g.…”

Section: Introductionmentioning

confidence: 99%

Clearing the hurdle: The mass of globular cluster systems as a function of host galaxy mass

Eadie,

Harris,

Springford

2021

Preprint

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Current observational evidence suggests that all large galaxies contain globular clusters (GCs), while the smallest galaxies do not. Over what galaxy mass range does the transition from GCs to no GCs occur? We investigate this question using galaxies in the Local Group, nearby dwarf galaxies, and galaxies in the Virgo Cluster Survey. We consider four types of statistical models: (1) logistic regression to model the probability that a galaxy of stellar mass M * has any number of GCs; (2) Poisson regression to model the number of GCs versus M * , (3) linear regression to model the relation between GC system mass (log M gcs ) and host galaxy mass (log M ), and (4) a Bayesian lognormal hurdle model of the GC system mass as a function of galaxy stellar mass for the entire data sample. From the logistic regression, we find that the 50% probability point for a galaxy to contain GCs is M * = 10 6.8 M . From post-fit diagnostics, we find that Poisson regression is an inappropriate description of the data. Ultimately, we find that the Bayesian lognormal hurdle model, which is able to describe how the mass of the GC system varies with M * even in the presence of many galaxies with no GCs, is the most appropriate model over the range of our data. In an Appendix, we also present photometry for the little-known GC in the Local Group dwarf Ursa Major II.

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“…[105], the value of the DM density in globular clusters is highly uncertain and under debate. Although values of 10 3 GeV/cm 3 could be expected if globular clusters form within DM subhalos before falling into galactic halos [107], tidal stripping by subsequent mergers [108] provides a very efficient way of depleting DM in these systems, leaving them dominated today by just the stellar component [109]. The observation that the present-day dynamics of globular clusters can be explained without the need of DM suggests that these systems might form in molecular clouds in the gaseous disk of the galaxy instead of in DM overdensities [110][111][112].…”

Section: Dm Indirect Detectionmentioning

confidence: 99%

A little theory of everything, with heavy neutral leptons

Cline

Puel

Toma

2020

J. High Energ. Phys.

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Recently a new model of "Affleck-Dine inflation" was presented, that produces the baryon asymmetry from a complex inflaton carrying baryon number, while being consistent with constraints from the cosmic microwave background. We adapt this model such that the inflaton carries lepton number, and communicates the lepton asymmetry to the standard model baryons via quasi-Dirac heavy neutral leptons (HNLs) and sphalerons. One of these HNLs, with mass 4.5 GeV, can be (partially) asymmetric dark matter (DM), whose asymmetry is determined by that of the baryons. Its stability is directly related to the vanishing of the lightest neutrino mass. Neutrino masses are generated by integrating out heavy sterile neutrinos whose mass is above the inflation scale. The model provides an economical origin for all of the major ingredients missing from the standard model: inflation, baryogenesis, neutrino masses, and dark matter. The HNLs can be probed in fixed-target experiments like SHiP, possibly manifesting N -N oscillations. A light singlet scalar, needed for depleting the DM symmetric component, can be discovered in beam dump experiments and searches for rare decays, possibly explaining anomalous events recently observed by the KOTO collaboration. The DM HNL is strongly constrained by direct searches, and could have a cosmologically interesting self-interaction cross section.

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Globular Cluster Systems and Galaxy Formation

Cited by 38 publications

References 137 publications

Diversity of nuclear star cluster formation mechanisms revealed by their star formation histories

Diversity of nuclear star cluster formation mechanisms revealed by their star formation histories

Clearing the hurdle: The mass of globular cluster systems as a function of host galaxy mass

A little theory of everything, with heavy neutral leptons

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