Erosion of globular cluster systems: the influence of radial anisotropy, central black holes and dynamical friction

Abstract

We present the adaptable MUESLI code for investigating dynamics and erosion processes of globular clusters (GCs) in galaxies. MUESLI follows the orbits of individual clusters and applies internal and external dissolution processes to them. Orbit integration is based on the self-consistent field method in combination with a timetransformed leapfrog scheme, allowing us to handle velocity-dependent forces like triaxial dynamical friction.In a first application, the erosion of globular cluster systems (GCSs) in elliptical galaxies is investigated. Observations show that massive ellipticals have rich, radially extended GCSs, while some compact dwarf ellipticals contain no GCs at all.For several representative examples, spanning the full mass scale of observed elliptical galaxies, we quantify the influence of radial anisotropy, galactic density profiles, SMBHs, and dynamical friction on the GC erosion rate. We find that GC number density profiles are centrally flattened in less than a Hubble time, naturally explaining observed cored GC distributions. The erosion rate depends primarily on a galaxy's mass, half-mass radius and radial anisotropy. The fraction of eroded GCs is nearly 100% in compact, M 32 like galaxies and lowest in extended and massive galaxies. Finally, we uncover the existence of a violent tidal disruption dominated phase which is important for the rapid build-up of halo stars.

The effects of orbital inclination on the scale size and evolution of tidally filling star clusters

“…Since disk and triaxial elliptical galaxies have nonspherically symmetric potentials, and most Galactic globular clusters have non-circular orbits (Dinescu et al 1999;Casetti-Dinescu et al 2007, assuming that a cluster experiences a static tidal field as it evolves is clearly incorrect. Various works have studied the evolution of clusters in non-static tidal fields (Baumgardt & Makino 2003;Giersz & Heggie 2009Renaud et al 2011;Webb et al 2013;Brockamp et al 2014;Madrid et al 2014), where the easiest approach is to first consider clusters with eccentric orbits in a spherically symmetric tidal field. These studies have shown that a cluster on an eccentric orbit will lose mass faster than if it has a circular orbit at apogalacticon Ra, but slower than if it has a circular orbit at perigalacticon Rp.…”

Unveiling Gargantua: A new search strategy for the most massive central cluster black holes

“…The models are generated in equilibrium (including central black holes) with the procedure described in Brockamp et al (2014). To exclude any dynamical instabilities related to anisotropic models (i.e., tangetially biased within R break and radially biased at large radii), we only use models with an isotropic velocity distribution.…”

“…Finally, the amount of swallowed particles by the adiabatically growing black hole ranged from insignificant to small values when compared with the gas accretion rates and is therefore not discussed. Figure 3 shows the dynamical response of the projected (2D) density profiles to adiabatically growing SMBHs obtained with the MUESLI software (Brockamp et al 2014). We use dimensionless model units, R, ρ 2D , for a better comparison.…”

“…In the main part of this paper (Sect. 3) we perform computations with the newly developed M software (Brockamp et al 2014) to evaluate the impact of the (compiled) SMBH growth rates on the innermost surface brightness profiles. In Sect.…”

The effect of primordial mass segregation on the size scale of globular clusters

“…This mass-loss will depend on the physical processes within the cluster (e.g. core collapse, binary formation, stellar evolution), but it will also be sensitive to the galactic tide within which it orbits (e.g., Giersz & Heggie 1997;Hurley 2007;Heggie & Giersz 2008;Gieles, Heggie, & Zhao 2011;Brockamp et al 2014). This effect can be amplified by unsteady tides (tidal shocks) when a cluster traverses the Galactic plane, or passes the bulge.…”