Streams Going Notts: The tidal debris finder comparison project

Abstract

While various codes exist to systematically and robustly find haloes and subhaloes in cosmological simulations (Knebe et al., 2011, Onions et al., 2012), this is the first work to introduce and rigorously test codes that find tidal debris (streams and other unbound substructure) in fully cosmological simulations of structure formation. We use one tracking and three non-tracking codes to identify substructure (bound and unbound) in a Milky Way type simulation from the Aquarius suite (Springel et al., 2008) and post-process their output with a common pipeline to determine the properties of these substructures in a uniform way. By using output from a fully cosmological simulation, we also take a step beyond previous studies of tidal debris that have used simple toy models. We find that both tracking and non-tracking codes agree well on the identification of subhaloes and more importantly, the {\em unbound tidal features} associated with them. The distributions of basic properties of the total substructure distribution (mass, velocity dispersion, position) are recovered with a scatter of $\sim 20$. Using the tracking code as our reference, we show that the non-tracking codes identify complex tidal debris with purities of $\sim 40$. Analysing the results of the substructure finders, we find that the general distribution of {\em substructures} differ significantly from the distribution of bound {\em subhaloes}. Most importantly, both bound and unbound {\em substructures} together constitute $\sim 18$ of the host halo mass, which is a factor of $\sim 2$ higher than the fraction in self-bound {\em subhaloes}. However, this result is restricted by the remaining challenge to cleanly define when an unbound structure has become part of the host halo. Nevertheless, the more general substructure distribution provides a more complete picture of a halo's accretion history.

19 pages, 12 figures, accepted for publication in MNRAS

References in corpus (9)

• Results from a Low-Energy Analysis of the CDMS II Germanium Data
• Tracing Galaxy Formation with Stellar Halos II: Relating Substructure in Phase- and Abundance-Space to Accretion Histories
• Phase-space structure in the local dark matter distribution and its signature in direct detection experiments
• SubHaloes going Notts: The SubHalo-Finder Comparison Project
• The fine-grained phase-space structure of Cold Dark Matter halos
• Disassembling the Galaxy with angle-action coordinates
• The Tidal Streams of Disrupting Subhaloes in Cosmological Dark Matter Haloes
• Subhaloes gone Notts: Spin across subhaloes and finders
• Subhaloes in Scale-Free Cosmologies

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