CASCO: Cosmological and AStrophysical parameters from Cosmological simulations and Observations

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.