The Santa Fe Light Cone Simulation Project. I. Confusion and the Warm-Hot Intergalactic Medium in Upcoming Sunyaev-Zel'dovich Effect Surveys

We present the first results from a new generation of simulated large sky coverage (~100 deg²) Sunyaev-Zel'dovich effect (SZE) cluster surveys using the cosmological adaptive mesh refinement N-body/hydro code Enzo. We have simulated a very large (512³ h^-3 Mpc³) volume with unprecedented dynamic range. We have generated simulated light cones to match the resolution and sensitivity of current and future SZE instruments. Unlike many previous studies of this type, our simulation includes unbound gas, where an appreciable fraction of the baryons in the universe reside. We have found that cluster line-of-sight overlap may be a significant issue in upcoming single-dish SZE surveys. Smaller beam surveys (~1') have more than one massive cluster within a beam diameter 5%-10% of the time, and a larger beam experiment like Planck has multiple clusters per beam 60% of the time. We explore the contribution of unresolved halos and unbound gas to the SZE signature at the maximum decrement. We find that there is a contribution from gas outside clusters of ~16% per object, on average, for upcoming surveys. This adds both bias and scatter to the deduced value of the integrated SZE, increasing difficulty in accurately calibrating a cluster Y-M relationship. Finally, we find that in images where objects with M > 5 × 10¹³ M_☉ have had their SZE signatures removed, roughly a third of the total SZE flux remains. This gas exists at least partially in the warm-hot intergalactic medium (WHIM) and will possibly be detectable with the upcoming generation of SZE surveys.