Sahyadri: a simulation suite for the cosmology dependence of the cosmic web

Abstract

We present Sahyadri, a suite of cosmological N-body simulations designed to enable precision studies of the low-redshift Universe with next-generation spectroscopic surveys. Sahyadri includes systematic variations of four cosmological parameters around Planck 2018 constraints, with seed-matched initial conditions enabling cosmological parameter derivatives. It is planned to ultimately extend to six parameters. Each simulation evolves 20483 particles in a periodic box of side length 200 h-1 Mpc, yielding a particle mass of mp = 8.1 × 107h-1M⊙ in the fiducial Planck 2018 cosmology. This resolution enables robust identification of dark matter halos down to Mmin = 3.2 × 109h-1M⊙, which represents a factor of ∼25 improvement over the AbacusSummit suite, and is over two orders of magnitude better than the Quijote and Aemulus suites. We estimate that approximately 40% of DESI BGS galaxies at redshift z < 0.15 — roughly 1.6 million objects — reside in halos accessible to Sahyadri but beyond the reach of existing parameter-varying simulation suites. We demonstrate Sahyadri's capabilities through measurements of the matter power spectrum, halo mass function and power spectrum, and beyond 2-point statistics such as the Voronoi volume function and kth nearest neighbour statistics, showing excellent agreement with theoretical predictions and significant sensitivity to Ωm variations. We implement a custom compression scheme reducing storage requirements by a factor of ∼3 while maintaining sub-percent clustering accuracy. Key data products will be made publicly available.