# SURFS: Riding the waves with Synthetic UniveRses For Surveys

P.J. Elahi, C. Welker, C. Power, Claudia del P Lagos, A. Robotham, R. Cañas, R. Poulton

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40 Citations (Web of Science)
We present the Synthetic UniveRses For Surveys (surfs) simulations, a set of N-body/Hydro simulations of the concordance Λ Cold Dark Matter (ΛCDM) cosmology. These simulations use Planck cosmology, contain up to 10 billion particles, and sample scales and halo masses down to 1 kpc and 108 M⊙. We identify and track haloes from z = 24 to today using a state-of-the-art 6D halo finder and merger tree builder. We demonstrate that certain properties of haloes merger trees are numerically converged for haloes composed of ≳100 particles. Haloes smoothly grow in mass, Vmax, with the mass history characterized by log M(a) ∝ exp [−(a/β)α], where a is the scale factor, α(M) ≈ 0.8 & β(M) ≈ 0.024, with these parameters decreasing with decreasing halo mass. Subhaloes follow power-law cumulative mass and velocity functions, i.e. n( > f) ∝ f−α with αM = 0.83 ± 0.01 and $$\alpha _{V_{\rm max}}=2.13\pm 0.03$$ for mass and velocity, respectively, independent of redshift, as seen in previous studies. The halo-to-halo scatter in amplitude is 0.9 dex. The number of subhaloes in a halo weakly correlates with a halo's concentration c and spin λ:haloes of high c and low λ have 60 per cent more subhaloes than similar mass haloes of low c and high λ. High cadence tracking shows subhaloes are dynamic residents, with 25 per cent leaving their host halo momentarily, becoming a backsplash subhalo, and another 20 per cent changing hosts entirely, in agreement with previous studies. In general, subhaloes have elliptical orbits, e ≈ 0.6, with periods of $$2.3^{+2.1}_{-1.7}$$ Gyrs. Subhaloes lose most of their mass at pericentric passage with mass loss rates of ∼ 40 per cent Gyr−1. These catalogues will be made publicly available.