Mass-loss in tidally stripped systems: the energy-based truncation method

Abstract

The ability to accurately predict the evolution of tidally stripped haloes is important for understanding galaxy formation and testing the properties of dark matter. Most studies of substructure evolution make predictions based on empirical models of tidal mass loss that are calibrated using numerical simulations. This approach can be accurate in the cases considered, but lacks generality and does not provide a physical understanding of the processes involved. Recently, we demonstrated that truncating NFW distribution functions sharply in energy results in density profiles that resemble those of tidally stripped systems, offering a path to constructing physically motivated models of tidal mass loss. In this work, we review calculations of mass loss based on energy truncation alone, and then consider what secondary effects may modulate mass loss beyond this. We find that a combination of dependence on additional orbital parameters and variations in individual particle energies over an orbit results in a less abrupt truncation in energy space as a subhalo loses mass. Combining the energy truncation approach with a simple prediction for the mass-loss rate, we construct a full model of mass loss that can accurately predict the evolution of a subhalo in terms of a single parameter η eff . This parameter can be fully determined from the initial orbital and halo properties, and does not require calibration with numerical simulations.

The tidal evolution of dark matter substructure – II. The impact of artificial disruption on subhalo mass functions and radial profiles

“…Importantly, the performance of the model is strong over the full range of η, spanning from orbits that are close to radial (η = 0.1) to those that are close to circular (η = 0.9), a feat that has proven difficult for previous semi-analytical models of subhalo mass evolution (cf. Peñarrubia et al 2010;Drakos et al 2020). Although not shown, we emphasize that the model performs comparably for other configurations as well.…”

“…Although it is tempting to compare our best-fitting value for α to that of previous semi-analytical models that rely on equation ( 7), such a comparison is frustrated by the fact that different studies have used different forms for t char and/or l t (see Drakos et al 2020 for detailed discussions). In addition, none of the previous studies have accounted for the detailed evolution of the subhalo density profile (as in, e.g.…”

The First Three Seconds: a Review of Possible Expansion Histories of the Early Universe

“…Any subhalo material lying beyond the tidal radius is expected to be stripped [for a review of tidal radius definitions, see 831]. A refinement to this approach involves conditioning tidal stripping on the energy of subhalo material instead of its radius [832]. Beyond this tidal truncation picture, material below the tidal radius is also heated by tidal forces, and the subhalo undergoes internal dynamics in response.…”

Structure and kinematics of tidally limited satellite galaxies in LCDM

“…For simplicity, we compute binding energies in the rest frame of the subhalo and do not include the gravitational effects of the main halo. Recall that our analysis focusses on the subhalo remnant structure at apocentre, where the subhalo spends most of its orbital time and where the effect of the main halo is minimal.highly-stripped systems, where the least bound particles are the most likely to be stripped away by tides.Indeed, as shown in Fig.4, as tides strip the subhalo the energy distribution is gradually trimmed off, leaving only the initially most bound particles in the final remnant (see alsoDrakos et al 2020;Stücker et al 2021;Amorisco 2021). The truncation is quite sharp, and may be approximated by a "filter function",d𝑁/dE | i,t = d𝑁/dE | i 1 + 𝑎 E/E mx,t 𝑏 ,(9)…”