Halo concentrations from extended Press-Schechter merger histories

Understand

We apply the model relating halo concentration to formation history proposed by Ludlow et al.

• to merger trees generated using an algorithm based on excursion set theory.
• We find that while the model correctly predicts the median relation between halo concentration and mass, it underpredicts the scatter in concentration at fixed mass.
• Since the same model applied to N-body merger trees predicts the correct scatter, we postulate that the missing scatter is due to the lack of any environmental dependence in merger trees derived from excursion set theory.