Michela Silvestrini

Small-scale discrepancies in the standard Lamda cold dark matter paradigm have motivated the exploration of alternative dark matter (DM) models, such as warm dark matter (WDM). In our work, we investigate the constraining power of galaxy scaling relations on cosmological, astrophysical, and WDM parameters using a joint analysis of multiresolution hydrodynamic simulations and observational data. Our study is based on the DREAMS project and combines large-volume uniform-box simulations with high-resolution Milky Way (MW) zoom-in runs exploring a ΛWDM cosmology. To ensure consistency between the different simulation sets, we applied calibrations to account for resolution effects, which allowed us to better exploit the complementary strengths of the two suites. We compared the simulated relations, such as stellar size, DM mass, and fraction, within the stellar half-mass radius and the total-to-stellar mass ratio with two complementary galaxy samples: the Spitzer Photometry and Accurate Rotation Curves catalog, providing resolved kinematics for nearby spirals, and the Local Volume Database catalog, which includes structural and dynamical measurements for dwarf galaxies in the Local Volume. By applying a bootstrap-based fitting procedure, we show that key cosmological parameters (Ω _m , σ ₈ ) and supernova feedback strength can be recovered with good accuracy, particularly from the uniform-box simulations. Although the WDM particle mass remains unconstrained, the MW zoom-in simulations reveal subtle WDM-induced trends, especially at low stellar masses, in the scaling relations of both the DM mass and the total-to-stellar mass ratio within the stellar half-mass radius. Additionally, we find that the galaxy abundance as a function of total stellar mass shows a measurable dependence on WDM particle mass, with a suppression at log ₁₀ M _* / M _⊙ ≲ 8 that appears separable from the impact of feedback, suggesting this observable is a valuable complementary probe. Our results highlight the importance of combining simulations at multiple resolutions with diverse observational catalogs to jointly constrain baryonic processes and DM properties. In particular, future low-mass galaxy surveys such as Euclid will play a crucial role in tightening the constraints on alternative DM scenarios through joint structural and statistical analyses. At the same time, higher-resolution simulations will be essential to fully capturing the small-scale features and improving the discriminatory power of such analyses, especially in the context of WDM.

Physical processes can influence the formation and evolution of galaxies in diverse ways. It is essential to validate their incorporation into cosmological simulations by testing them against real data encompassing various types of galaxies and spanning a broad spectrum of masses and galaxy properties. For these reasons, in this second paper of the CASCO series, we compare the structural properties and dark matter content of early-type galaxies taken from the CAMELS IllustrisTNG cosmological simulations to three different observational datasets (SPIDER, ATLAS^3D, and MaNGA DynPop), to constrain the value of cosmological and astrophysical feedback parameters, and we compare the results with those obtained comparing the simulation expectations with late-type galaxies. We consider the size-mass, internal DM fraction-mass, and internal DM mass-stellar mass relations for all the simulations, and search for the best-fit simulation for each set of observations. For SPIDER, we find values for the cosmological parameters in line with both the literature and the results obtained from the comparison between simulations and late-type galaxies; results for the supernovae feedback parameters are instead opposite with respect to the previous results based on late-type galaxies. For ATLAS^3D, we find similar values as from SPIDER for the cosmological parameters, but we find values for the supernovae feedback parameters more in line with what we found for late-type galaxies. From MaNGA DynPop, we find extreme values for the cosmological parameters, while the supernovae feedback parameters are consistent with ATLAS^3D results. When considering the full MaNGA DynPop sample, including both late- and early-type galaxies, no single simulation can reproduce the full variety in the observational datasets. The constraints depend strongly on the specific properties of each observational trend, making it difficult to find a simulation matching all galaxy types, indicating the existence of limitations in the ability of simulations in reproducing the observations.