The MAGPI Survey: co-evolution of baryons and dark matter in star-forming disk-like galaxies at 0.1 z 0.85

We present a comprehensive analysis of the dark matter (DM) content and its structural dependence in star-forming disk-like galaxies at intermediate redshifts (0.1 z 0.85), utilizing spatially resolved kinematic data from the MAGPI survey. We report the following: (1) Low stellar mass galaxies (M star < 10 9.5, M) are strongly DM dominated across all radii, with average f DM about 0.85, while high-mass (M star > 10 10.5, M) systems exhibit relatively low DM fractions in their inner regions (f DM about 0.47) which is equivalent to local massive disk galaxies (e.g., Milky Way and Andromeda). This suggests a mass-dependent structural dichotomy, most-likely governed by a combination of internal galactic processes and environmental influences. (2) A tight inverse correlation between f DM and baryon mass surface density (Σ bar), with intrinsic scatter of about 0.11 dex. This is consistent with an inside-out baryon assembly scenario and suggests that the fundamental structural correlations of galaxies were already established by z about 0.85. (3) No significant evolution in f DM with redshift across the MAGPI window, and when combined with higher-redshift (0.6 at most z at most 1.5) data from Sharma et al. 2025, we quantitatively show that the reported decline in f DM(z) is most-likely due to observational biases against low-mass systems at z > 1. These results offer empirical evidence for a scenario in which disk-like galaxies evolve through a co-regulated build-up of baryonic and DM components, preserving internal structural regularities (such as the total mass distribution and rotation-curve shape) throughout cosmic time.