Farpoint: A High-Resolution Cosmology Simulation at the Gpc Scale

Frontiere, N., Heitmann, K., Rangel, E., Larsen, P., Pope, A., Sultan, I., Uram, T., Habib, S., Rizzi, S., Insley, J. 2021. arXiv:2109.01956 [astro-ph.CO]


In this paper we introduce the Farpoint simulation, the latest member of the Hardware/Hybrid Accelerated Cosmology Code (HACC) gravity-only simulation family. The domain covers a volume of (1000$h^{-1}$Mpc)$^3$ and evolves close to two trillion particles, corresponding to a mass resolution of $m_p\sim 4.6\cdot 10^7 h^{-1}$M$_\odot$. These specifications enable comprehensive investigations of the galaxy-halo connection, capturing halos down to small masses. Further, the large volume resolves scales typical of modern surveys with good statistical coverage of high mass halos. The simulation was carried out on the GPU-accelerated system Summit, one of the fastest supercomputers currently available. We provide specifics about the Farpoint run and present an initial set of results. The high mass resolution facilitates precise measurements of important global statistics, such as the halo concentration-mass relation and the correlation function down to small scales. Selected subsets of the simulation data products are publicly available via the HACC Simulation Data Portal.

The Last Journey. II. SMACC – Subhalo Mass-loss Analysis using Core Catalogs

Sultan, I., Frontiere, N., Habib, S., Heitmann, K., Kovacs, E., Larsen, P., Rangel, E. 2021. The Astrophysical Journal, 913, 109


This paper introduces Subhalo Mass-loss Analysis using Core Catalogs (SMACC). SMACC adds a mass model to substructure merger trees based on halo “core tracking.” Our approach avoids the need for running expensive subhalo finding algorithms and instead uses subhalo mass-loss modeling to assign masses to halo cores. We present details of the SMACC methodology and demonstrate its excellent performance in describing halo substructure and its evolution. Validation of the approach is carried out using cosmological simulations at significantly different resolutions. We apply SMACC to the 1.24-trillion-particle Last Journey simulation and construct core catalogs with the additional mass information. These catalogs can be readily used as input to semianalytic models or subhalo abundance matching approaches to determine approximate galaxy distributions, as well as for in-depth studies of small-scale structure evolution.

The Last Journey. I. An Extreme-Scale Simulation on the Mira Supercomputer

Heitmann, K., Frontiere, N., Rangel, E., Larsen, P., Pope, A., Sultan, I., Uram, T., Habib, S., Finkel, H., Korytov, D., Kovacs, E., Rizzi, S., Insley, J., Knowles, J. Y.K. 2021. The Astrophysical Journal Supplement Series, 252, 19


The Last Journey is a large-volume, gravity-only, cosmological N-body simulation evolving more than 1.24 trillion particles in a periodic box with a side-length of 5.025Gpc. It was implemented using the HACC simulation and analysis framework on the BG/Q system, Mira. The cosmological parameters are chosen to be consistent with the results from the Planck satellite. A range of analysis tools have been run in situ to enable a diverse set of science projects, and at the same time, to keep the resulting data amount manageable. Analysis outputs have been generated starting at redshift $z \sim 10$ to allow for construction of synthetic galaxy catalogs using a semi-analytic modeling approach in post-processing. As part of our in situ analysis pipeline we employ a new method for tracking halo sub-structures, introducing the concept of subhalo cores. The production of multi-wavelength synthetic sky maps is facilitated by generating particle lightcones in situ, also beginning at $z \sim 10$. We provide an overview of the simulation set-up and the generated data products; a first set of analysis results is presented. A subset of the data is publicly available.