The tidal streams of disrupting subhaloes in cosmological dark matter haloes

Abstract

We present a detailed analysis of the properties of tidally stripped material from disrupting substructure haloes or subhaloes in a sample of high-resolution cosmological N-body host haloes ranging from galaxy-to cluster-mass scales. We focus on devising methods to recover the infall mass and infall eccentricity of subhaloes from the properties of their tidally stripped material (i.e. tidal streams). Our analysis reveals that there is a relation between the scatter of stream particles about the best-fitting debris plane and the infall mass of the progenitor subhalo. This allows us to reconstruct the infall mass from the spread of its tidal debris in space. We also find that the spread in radial velocities of the debris material (as measured by an observer located at the centre of the host) correlates with the infall eccentricity of the subhalo, which allows us to reconstruct its orbital parameters. We devise an automated method to identify the leading and trailing arms that can, in principle at least, be applied to observations of stellar streams from satellite galaxies. This method is based on the energy distribution of material in the tidal stream. Using this method, we show that the masses associated with the leading and trailing arms differ. While our analysis indicates that tidal streams can be used to recover certain properties of their progenitor subhaloes (and consequently satellites), we do not find strong correlations between host halo properties and stream properties. This likely reflects the complicated relationship between the stream and the host, which in a cosmological context is characterized by a complex mass accretion history, an asymmetric mass distribution and the abundance of substructure. Finally, we confirm that the so-called 'backsplash' subhalo population is present not only in galaxy cluster haloes but also in galaxy haloes. The orbits of backsplash subhaloes brought them inside the virial radius of their host at some earlier time, but they now reside in its outskirts at the present-day, beyond the virial radius. Both backsplash and bound subhaloes experience similar mass loss, but the contribution of the backsplash subhaloes to the overall tidal debris field is negligible.

Tracing Galaxy Formation with Stellar Halos. II. Relating Substructure in Phase and Abundance Space to Accretion Histories

“…where M gal is the mass of the parent galaxy enclosed within the pericenter of the satellite's orbit (e.g., Johnston 1998;Warnick et al 2008). The range in orbital energies corresponds to a range in orbital time periods, and this leads to the debris spreading along the orbit to form tidal streams.…”

Halo streams in the solar neighborhood

“…The leading tail contains stars at lower energies than the trailing tail, so each time stars get stripped from the satellite, e.g., through tidal shocks at pericenter, roughly two groupings of stars at distinct energies result (Johnston 1998;Meza et al 2005;Choi et al 2007). Warnick et al (2008) proposed that this energy difference could be used for the distinction between leading and trailing stars even after significant dispersion throughout the Galaxy. As pointed out by Choi et al (2007), (dark matter) particles in the leading tail continue to be decelerated by their satellite's gravity and fall towards the central regions of the host.…”

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

“…The original cosmological N-body simulation was performed with an adaptive mesh refinement code MLAPM (Knebe et al 2001), and is fully described in Warnick & Knebe (2006) and Warnick et al (2008). Each dark matter particle has a mass ∼1.6 × 10 8 h −1 M , and the highest spatial resolution is ∼2 kpc.…”