Modeling submillimeter galaxies in cosmological simulations: Contribution to the cosmic star formation density and predictions for future surveys

Context. Submillimeter galaxies (SMGs) constitute a key population of bright star-forming galaxies at high-redshift. These galaxies challenge galaxy formation models, particularly regarding the reproduction of their observed number counts and redshift distributions. Furthermore, although SMGs contribute significantly to the cosmic star formation rate density (SFRD), their precise role remains uncertain. Upcoming surveys, such as the Ultra Deep Survey with the TolTEC camera, are expected to offer valuable insights into SMG properties and their broader impact in the Universe. Aims. Robust modeling of SMGs in a cosmological representative volume is necessary to investigate their nature in preparation for next-generation submillimeter surveys. Here, we test different parametric models for SMGs in large-volume hydrodynamical simulations, assess their contribution to the SFRD, and build expectations for future submillimeter surveys. Methods. We implement and test parametric relations derived from radiative transfer calculations across three cosmological simulation suites: EAGLE, IllustrisTNG, and FLAMINGO. We place particular emphasis on the FLAMINGO simulations due to their large volume and robust statistical sampling of SMGs. Based on the model that best reproduces observational number counts, we forecast submillimeter fluxes within the simulations, analyze the properties of SMGs, and evaluate their evolution over cosmic time. Results. Our results show that the FLAMINGO simulation reproduces the observed redshift distribution and source number counts of SMGs without requiring a top-heavy initial mass function. On the other hand, the EAGLE and IllustrisTNG simulations show a deficit of bright SMGs. We find that SMGs with S 850 > 1 mJy contribute up to ∼27% of the cosmic SFRD at z ∼ 2.6 in the FLAMINGO simulation, which is consistent with recent observations. Flux density functions reveal a rise in SMG abundance from z = 6 to z = 2.5 that is followed by a sharp decline in the number of brighter SMGs from z = 2.5 to z = 0. Leveraging the SMG population in FLAMINGO, we forecast that the TolTEC UDS will detect ∼80 000 sources over 0.8 deg 2 at 1.1 mm (at the 4 σ detection limit), capturing about 50% of the cosmic SFRD at z ∼ 2.5.