The boosted potential

Abstract

The global gravitational potential, φ, is not commonly employed in the analysis of cosmological simulations, since its level sets do not show any clear correspondence to the underlying density field and its persistent structures. Here, we show that the potential becomes a locally meaningful quantity when considered from a boosted frame of reference, defined by subtracting a uniform gradient term $\phi _{\rm {boost}}(\boldsymbol{x}) = \phi (\boldsymbol{x}) + \boldsymbol{x} \cdot \boldsymbol{a}_0$ with acceleration $\boldsymbol{a}_0$. We study this ‘boosted potential’ in a variety of scenarios and propose several applications: (1) The boosted potential can be used to define a binding criterion that naturally incorporates the effect of tidal fields. This solves several problems of commonly-used self-potential binding checks: i) it defines a tidal boundary for each halo, ii) it is much less likely to misidentify caustics as haloes (specially in the context of warm dark matter cosmologies), and iii) performs better at identifying virialized regions of haloes – yielding to the expected value of 2 for the virial ratio. (2) This binding check can be generalized to filaments and other cosmic structures. (3) The boosted potential facilitates the understanding of the disruption of satellite subhaloes. We propose a picture where most mass loss is explained through a lowering of the escape energy through the tidal field. (4) We discuss the possibility of understanding the topology of the potential field in a way that is independent of constant offsets in the first derivative $\boldsymbol{a}_0$. We foresee that this novel perspective on the potential can help to develop more accurate models and improve our understanding of structure formation. (We shortened some sentences in the abstract to be below 250 words.)

Large-scale dark matter simulations

“…This is also motivated by the fact that a constant (global) acceleration does not change the local dynamics of a system, see e.g. Stu ¨cker et al (2021a). Additionally, using tides avoids invoking the nonphysical scale e, and one has…”

“…On the other hand, ROCKSTAR has been shown to be relatively robust against numerical resolution (Leroy et al 2021), arguably thanks to the unbinding procedure. On the other hand, there is still arbitrariness in the definition of the phase-space metric, and the use of gravitational binding energy in the presence of accelerated frames and larger scale tidal fields Stu ¨cker et al (2021a).…”

Tidal Stripping in the Adiabatic Limit

“…On the other hand, Drakos et al (2017Drakos et al ( , 2020 have proposed energy truncation models as a simple approach to gain insights. Such models operate on the idea that the tidal stripping process peels orbiting subhaloes from the outside-in in energy space (Choi et al 2009;Stücker et al 2021), first removing particles that have the highest energy levels and then subsequently moving to smaller and smaller energies. Therefore, the particles that remain in the subhalo may be approximately inferred by a sharp truncation in initial energy space.…”

Large-scale dark matter simulations

“…This is also motivated by the fact that a constant (global) acceleration does not change the local dynamics of a system, see e.g. Stücker et al (2021a). Additionally, using tides avoids invoking the non-physical scale ε, and one has…”

“…On the other hand, ROCKSTAR has been shown to be relatively robust against numerical resolution (Leroy et al 2021), arguably thanks to the unbinding procedure. On the other hand, there is still arbitrariness in the definition of the phase-space metric, and the use of gravitational binding energy in the presence of accelerated frames and larger scale tidal fields Stücker et al (2021a).…”