摘要:
   The “observed” SFR-M* relation of galaxies and the cosmic star formation rate density represent both important canvases for our current knowledge of galaxy formation and are routinely used to constrain cosmological models/simulations. However, a rising number of authors report a severe tension between the SFRs published by different methodologies/groups. In this talk I present some disturbing limitations for both the simulated galaxy SFRs obtained from state-of-the-art cosmological simulations (EAGLE, IllustrisTNG, Simba, Katsianis et al. 2021a, 2021b) and observations (Katsianis et al 2020, 2021b). We employ cosmological simulations combined with radiative transfer and demonstrate that the adopted methodology to obtain galaxy SFRs heavily affects the results of observational studies which if they all used the same tracer/methodology/assumptions would be actually more “consistent” with each other (Katsianis et al. 2020). Besides observations, simulations are found to suffer from troubling limitations as well (Katsianis et al. 2021). Our findings reflect the need for the employed quenching schemes in state-of-the-art models to be reconsidered and involve feedback prescriptions that allow ’quenched galaxies’ to retain a small level of SF activity in order to be consistent with measurements of the specific star formation rate function at z ∼ 0. I also discuss briefly the limitations caused by resolution effects and their impact on comparisons with observational studies. Last, in an effort to make some sense from a chaos, where I do not know what to trust anymore I demonstrate that (possibly) the Observed star formation rate density can be described only by two parameters and a function that resembles a Γ distribution, like numerous physical processes in Nature .