The sensitivity of harassment to orbit: mass loss from early-type dwarfs in galaxy clusters

Abstract

We conduct a comprehensive numerical study of the orbital dependence of harassment on early-type dwarfs consisting of 168 different orbits within a realistic, Virgo-like cluster, varying in eccentricity and pericentre distance. We find harassment is only effective at stripping stars or truncating their stellar disks for orbits that enter deep into the cluster core. Comparing to the orbital distribution in cosmological simulations, we find that the majority of the orbits (more than three quarters) result in no stellar mass loss. We also study the effects on the radial profiles of the globular cluster systems of early-type dwarfs. We find these are significantly altered only if harassment is very strong. This suggests that perhaps most early-type dwarfs in clusters such as Virgo have not suffered any tidal stripping of stars or globular clusters due to harassment, as these components are safely embedded deep within their dark matter halo. We demonstrate that this result is actually consistent with an earlier study of harassment of dwarf galaxies, despite the apparent contradiction. Those few dwarf models that do suffer stellar stripping are found out to the virial radius of the cluster at redshift=0, which mixes them in with less strongly harassed galaxies. However when placed on phase-space diagrams, strongly harassed galaxies are found offset to lower velocities compared to weakly harassed galaxies. This remains true in a cosmological simulation, even when halos have a wide range of masses and concentrations. Thus phase-space diagrams may be a useful tool for determining the relative likelihood that galaxies have been strongly or weakly harassed.

Galaxy Zoo: the interplay of quenching mechanisms in the group environment★

“…However, there has been mounting evidence that RPS can only strip a galaxy of 40−60% of its gas supply (Fillingham et al 2016) and so may not be as effective a quenching mechanism as first thought (Emerick et al 2016). Therefore investigations of other environmentally driven quenching mechanisms, such as strangulation (Peng et al 2015;Hahn et al 2016;Maier et al 2016;Paccagnella et al 2016;Roberts et al 2016;van de Voort et al 2016) and harassment (high speed galaxy 'fly-by' gravitational interactions Bialas et al 2015;Smith et al 2015) are having a recent resurgence.…”

The Survey of Centaurus A's Baryonic Structures (SCABS) – II. The extended globular cluster system of NGC 5128 and its nearby environment

“…With that said, Crnojević et al detected clear signals of loops and streams that indicate that dwarfs are still being actively disrupted to the present day out to at least Rgc ≈ 120 (∼ 132 kpc), thus it is likely that past dwarf galaxy interactions may be behind the population of blue GCs at such distance from NGC 5128. Such interactions have recently been shown to produce preferential stripping of GC systems (Smith et al 2013;Smith et al 2015).…”

The Next Generation Virgo Cluster Survey. Xxii. Shell Feature Early-Type Dwarf Galaxies in the Virgo Cluster*

“…In all cases, the amount of light 21 Feldmann et al (2008) did not specifically focus on shell features, but their definition of "tidal features" should have also included the light from stars in shell features. 22 Located at beyond 450 kpc or nearly halfway out of the cluster virial radius, these galaxies may not feel a strong tidal interaction from the central potential (see Smith et al 2015, Figure 10). 23 We define the core as a regular morphological part of galaxies, see Figure 2.…”