Excursion Set Halos -- ExSHalos: A New Parameter Free Method for Fast Generation of Halo Catalogues

We develop a new, simple, fast and parameter-free method to construct dark matter halo catalogues. This method requires as inputs only the linear matter power spectrum and the threshold density for halo formation in linear theory. It directly uses excursion set ideas and Lagrangian perturbation theory to produce halo catalogues with the correct abundance, large scale power spectrum, bispectrum and velocity field. These halo catalogues can be used for the fast construction of mock galaxy catalogues, allowing for the evaluation of covariance matrices for multiple observables. Because of its robustness and predictive nature, this method can be easily adapted to produce catalogues with e.g. primordial non-Gaussianities, modified theories of gravity and non-standard dark energy models, enabling detailed studies of these models in the context of next-generation surveys. We implement this method in a C code, and present numerical comparisons with theoretical predictions as well as full N-body cosmological simulations.