Globular Clusters in the Fornax Dwarf Spheroidal Galaxy

Oh, K.; Lin, Da-Bin; Richer, Harvey B.

doi:10.1086/308477

Cited by 75 publications

(81 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several solutions to the timing problem have been proposed. Oh, Lin & Richer () suggested two ideas: first, that a population of black holes transferred energy to the clusters through close encounters and secondly, that a strong tidal interaction between the Milky Way and Fornax could inject energy into their orbits. There is no observational evidence for a population of black holes in the centre of Fornax, while the currently observed proper motion indicates that the orbit of Fornax around the Milky Way never takes it closer than at present (Dinescu et al ; Lux, Read & Lake ).…”

Section: Introductionmentioning

confidence: 99%

The mass distribution of the Fornax dSph: constraints from its globular cluster distribution

Cole¹,

Dehnen²,

Read

et al. 2012

Monthly Notices of the Royal Astronomical Society

118

181

View full text Add to dashboard Cite

Uniquely among the dwarf spheroidal (dSph) satellite galaxies of the Milky Way, Fornax hosts globular clusters. It remains a puzzle as to why dynamical friction has not yet dragged any of Fornax's five globular clusters to the centre, and also why there is no evidence that any similar star cluster has been in the past (for Fornax or any other tidally undisrupted dSph). We set up a suite of 2800 N‐body simulations that sample the full range of globular cluster orbits and mass models consistent with all existing observational constraints for Fornax. In agreement with previous work, we find that if Fornax has a large dark matter core, then its globular clusters remain close to their currently observed locations for long times. Furthermore, we find previously unreported behaviour for clusters that start inside the core region. These are pushed out of the core and gain orbital energy, a process we call ‘dynamical buoyancy’. Thus, a cored mass distribution in Fornax will naturally lead to a shell‐like globular cluster distribution near the core radius, independent of the initial conditions. By contrast, cold dark matter‐type cusped mass distributions lead to the rapid infall of at least one cluster within Δt = 1–2 Gyr, except when picking unlikely initial conditions for the cluster orbits (∼2 per cent probability), and almost all clusters within Δt = 10 Gyr. Alternatively, if Fornax has only a weakly cusped mass distribution, then dynamical friction is much reduced. While over Δt = 10 Gyr this still leads to the infall of one to four clusters from their present orbits, the infall of any cluster within Δt = 1–2 Gyr is much less likely (with probability 0–70 per cent, depending on Δt and the strength of the cusp). Such a solution to the timing problem requires (in addition to a shallow dark matter cusp) that in the past the globular clusters were somewhat further from Fornax than today; they most likely did not form within Fornax, but were accreted.

show abstract

Section: Introductionmentioning

confidence: 99%

The mass distribution of the Fornax dSph: constraints from its globular cluster distribution

Cole¹,

Dehnen²,

Read

et al. 2012

Monthly Notices of the Royal Astronomical Society

118

181

View full text Add to dashboard Cite

show abstract

“…In contrast, in small systems like dwarf galaxies, the drag force is far too strong (see Binney & Tremaine 2008, chapter 8). Thus, the GCs in dwarfs are presumed to lose their orbital energy and fall into the galactic centre by strong friction force on a time‐scale of the order of ∼1 Gyr (Tremaine 1976; Hernandez & Gilmore 1998; Oh, Lin & Richer 2000; Vesperini 2000, 2001; Goerdt et al 2006; Bekki 2010). Nevertheless, these GCs still do exist in many dwarf galaxies even now and are as old as the age of the Universe (e.g.…”

Section: Introductionmentioning

confidence: 99%

Corrective effect of many-body interactions in dynamical friction

Inoue¹

2011

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Dynamical friction is a fundamental and important phenomenon in astrophysics. The Chandrasekhar formula is a well-known analytical estimation of the effect. However, current astrophysicists have realized that the formula is not correct in some cases because of several approximations dared in the formulation and/or complex non-linearities in the real universe. For example, it has been indicated that the dynamical friction doesn't work in cored density profiles (constant density in the central region) despite that the Chandrasekhar formula predicts drag force even in the constant densities. In the former half of this paper, I discuss by N-body simulations that many-body interactions are also important in actual dynamical friction though derivation of the Chandrasekhar formula is based on the assumption of two-body interaction. In the simulation, the many-body interactions are caused by a very small number of field particles co-rotating with a perturber. However, the contribution from the many-body interactions accounts for a non-negligible fraction of the actual dynamical friction. In the latter half, I discuss why the cored profiles suppress the dynamical friction. One possible explanation is that corrective effect of the many-body interactions drive orbital motion of the perturber. The cessation of dynamical friction by this corrective effect would be feasible even in shallow cusp density profiles although the shallow cusp may evolve into a constant density.Comment: 11 pages, 17 figures, accepted for publication in MNRA

show abstract

“…In fact, it can help in discriminating the various scenarios proposed for their formation (see e.g. Oh & Lin 2000; Oh, Lin & Richer 2000; Fellhauer & Kroupa 2002; Fellhauer et al 2002; Bekki et al 2004; Capuzzo‐Dolcetta & Miocchi 2008, hereafter CM08; Goerdt et al 2008). At this regard, we cite the recent observational evidence of the existence of a very young and massive star cluster in NGC 2139, located 2 arcsec offset from the kinematical centre of the host galaxy, suggesting a formation that was independent and non‐coeval with that of the galactic bulge and, moreover, the observed environment is such that the system can decay to the centre in a time so short to keep intact its structure and become what is normally called NC (Andersen et al 2008, see also Böker et al 2002; Walcher et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Self-consistent simulations of nuclear cluster formation through globular cluster orbital decay and merging

Capuzzo–Dolcetta

Miocchi

2008

Monthly Notices of the Royal Astronomical Society: Letters

View full text Add to dashboard Cite

We present results of fully self‐consistent N‐body simulations of the motion of four globular clusters moving in the inner region of their parent galaxy. With regard to previous simplified simulations, we confirm merging and formation of an almost steady nuclear cluster, in a slightly shorter time. The projected surface density profile shows strong similarity to that of resolved galactic nuclei. This similarity reflects also in the velocity dispersion profile which exhibits a central colder component as observed in many nucleated galaxies.

show abstract

Globular Clusters in the Fornax Dwarf Spheroidal Galaxy

Cited by 75 publications

References 45 publications

The mass distribution of the Fornax dSph: constraints from its globular cluster distribution

The mass distribution of the Fornax dSph: constraints from its globular cluster distribution

Corrective effect of many-body interactions in dynamical friction

Self-consistent simulations of nuclear cluster formation through globular cluster orbital decay and merging

Contact Info

Product

Resources

About