Cusp or core? Revisiting the globular cluster timing problem in Fornax

Meadows, Noah; Navarro, Julio F.; Santos-Santos, Isabel; Benítez-Llambay, Alejandro; Frenk, Carlos S.

doi:10.1093/mnras/stz3280

Cited by 32 publications

(78 citation statements)

References 46 publications

(58 reference statements)

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“…On average, our DM halo mass estimates are an order of magnitude larger than previous determinations based on the stellar kinematics of the Fornax dSph, which suggest a DM halo mass of few × 10 9 M (Goerdt et al 2006;Boldrini et al 2019;Meadows et al 2020). However, our estimates are in good agreement with the abundancematching result of Read et al (2019), who found a total mass of ∼2 × 10 10 M .…”

Section: The Dm Halo Of the Fornax Dsphcontrasting

confidence: 73%

“…decay time-scales by assuming larger initial radii for the GCs rather than assuming that they formed at their present-day positions (e.g. Angus & Diaferio 2009;Cole et al 2012;Boldrini, Mohayaee & Silk 2019;Meadows et al 2020). However, the initial positions where the GCs were born are difficult to constrain due to the long time-scales involved.…”

Section: ; DImentioning

confidence: 99%

“…The main difference between haloes with a central core and those with a cusp is the fraction of tidally disrupted GCs, which is expected to be lower for the former case (e.g. Goerdt et al 2006;Meadows et al 2020). Thus, the number of Fornax GCs is not a reflection of whether or not the DM halo profile has a central core or cusp.…”

Section: The Number Of Gcs In Fornax-mass Dwarfsmentioning

confidence: 99%

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The survival of globular clusters in a cuspy Fornax

Shao

Cautun

Frenk

et al. 2021

Monthly Notices of the Royal Astronomical Society

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It has long been argued that the globular clusters (GCs) in the Fornax dwarf galaxy indicate that its dark matter halo is likely to have a shallow density profile with a core of size ∼1 kpc. We revisit this argument by investigating analogues of Fornax formed in E-MOSAICS, a cosmological hydrodynamical simulation that follows the formation and evolution of GCs in the eagle galaxy formation model. In eagle, Fornax-mass haloes are cuspy and well described by the Navarro-Frenk-White profile. We post-process the E-MOSAICS to account for GC orbital decay by dynamical friction, which is not included in the original model. Dynamical friction causes 33 per cent of GCs with masses $M_{\rm GC}\ge 4\times 10^4{~\rm M_\odot }$ to sink to the centre of their host with the majority being tidally disrupted before forming a nuclear star cluster. Fornax has a total of five GCs, an exceptionally large number compared to other galaxies of similar stellar mass. In the simulations, we find that only 3 per cent of the Fornax analogues have five or more GCs, while 30 per cent have only one and 35 per cent have none. We find that GC systems in satellites are more centrally concentrated than in field dwarfs, and that those formed in situ (45 per cent) are more concentrated than those that were accreted. The present-day radial distribution of GCs in E-MOSAICS Fornax analogues is indistinguishable from that in Fornax, demonstrating that the presence of five GCs in the central kiloparsec of Fornax is consistent with a cuspy dark matter halo.

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Section: The Dm Halo Of the Fornax Dsphcontrasting

confidence: 73%

Section: ; DImentioning

confidence: 99%

Section: The Number Of Gcs In Fornax-mass Dwarfsmentioning

confidence: 99%

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The survival of globular clusters in a cuspy Fornax

Shao

Cautun

Frenk

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…For the GC to merely arrive and survive in the centre after arrival, there are no strong requirements for the halo profile or orbital eccentricity. The time-scale for infall is to first order, set by the starting position in the host, with minimal dependence on the inner density profile slope (see also Meadows et al 2020). As shown in Section 5.3 however, there is a clear preference for the optimal solutions which also reproduce the GC structure (green points) to have initial starting positions for the GC of D gal, i 700 pc.…”

Section: Characteristics Of Successful Orbitsmentioning

confidence: 99%

“…This process of orbital inspiral is sensitive to the shape of the total density profile of the host galaxy, with the relatively high-mass ratios between GCs and dwarf galaxy hosts meaning that this process is expected to be important in the survival of the GC (Orkney et al 2019). For example, Petts, Read & Gualandris (2016) showed under which conditions the host galaxy's density profile may lead to the dynamical friction processes stalling, while Meadows et al (2020) further illustrated the similarity in dynamical friction time-scales in cored and cusped density profiles.…”

mentioning

confidence: 99%

Globular cluster ejection, infall, and the host dark matter halo of the Pegasus dwarf galaxy

Leaman

Ruiz-Lara

Cole

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Recent photometric observations revealed a massive, extended (MGC ≳ 105 M⊙; Rh ∼ 14 pc) globular cluster (GC) in the central region (D3D ≲ 100 pc) of the low-mass (M* ∼ 5 × 106 M⊙) dwarf irregular galaxy Pegasus. This massive GC offers a unique opportunity to study star cluster inspiral as a mechanism for building up nuclear star clusters, and the dark matter (DM) density profile of the host galaxy. Here, we present spectroscopic observations indicating that the GC has a systemic velocity of ΔV = 3 ± 8 km s−1 relative to the host galaxy, and an old, metal-poor stellar population. We run a suite of orbital evolution models for a variety of host potentials (cored to cusped) and find that the GC’s observed tidal radius (which is ∼3 times larger than the local Jacobi radius), relaxation time, and relative velocity are consistent with it surviving inspiral from a distance of Dgal ≳ 700 pc (up to the maximum tested value of Dgal = 2000 pc). In successful trials, the GC arrives to the galaxy centre only within the last ∼1.4 ± 1 Gyr. Orbits that arrive in the centre and survive are possible in DM haloes of nearly all shapes, however to satisfy the GC’s structural constraints a galaxy DM halo with mass MDM ≃ 6 ± 2 × 109 M⊙, concentration c ≃ 13.7 ± 0.6, and an inner slope to the DM density profile of −0.9 ≤ γ ≤ −0.5 is preferred. The gas densities necessary for its creation and survival suggest the GC could have formed initially near the dwarf’s centre, but then was quickly relocated to the outskirts where the weaker tidal field permitted an increased size and relaxation time – with the latter preserving the former during subsequent orbital decay.

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Nuclear star clusters

Neumayer

Seth

Böker³

2020

Astron Astrophys Rev

269

270

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We review the current knowledge about nuclear star clusters (NSCs), the spectacularly dense and massive assemblies of stars found at the centers of most galaxies. Recent observational and theoretical works suggest that many NSC properties, including their masses, densities, and stellar populations, vary with the properties of their host galaxies. Understanding the formation, growth, and ultimate fate of NSCs, therefore, is crucial for a complete picture of galaxy evolution. Throughout the review, we attempt to combine and distill the available evidence into a coherent picture of NSC evolution. Combined, this evidence points to a clear transition mass in galaxies of $$\sim 10^9\,M_\odot$$ ∼ 10 9 M ⊙ where the characteristics of nuclear star clusters change. We argue that at lower masses, NSCs are formed primarily from globular clusters that inspiral into the center of the galaxy, while at higher masses, star formation within the nucleus forms the bulk of the NSC. We also discuss the co-existence of NSCs and central black holes, and how their growth may be linked. The extreme densities of NSCs and their interaction with massive black holes lead to a wide range of unique phenomena including tidal disruption and gravitational-wave events. Finally, we review the evidence that many NSCs end up in the halos of massive galaxies stripped of the stars that surrounded them, thus providing valuable tracers of the galaxies’ accretion histories.

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Cusp or core? Revisiting the globular cluster timing problem in Fornax

Cited by 32 publications

References 46 publications

The survival of globular clusters in a cuspy Fornax

The survival of globular clusters in a cuspy Fornax

Globular cluster ejection, infall, and the host dark matter halo of the Pegasus dwarf galaxy

Nuclear star clusters

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