MaNGA DynPop – VI. Matter density slopes from dynamical models of 6000 galaxies versus cosmological simulations: the interplay between baryonic and dark matter

We try to understand the trends in the mass density slopes as a function of galaxy properties. We use the results from the best Jeans Anisotropic Modelling (JAM) of the integral-field stellar kinematics for near 6000 galaxies from the MaNGA DynPop project, with stellar masses of 10^9-12 M_⊙, including both early-type and late-type galaxies. We use the mass-weighted density slopes for the stellar γ_*, dark γ_ DM, and total γ_ T mass from the MaNGA DynPop project. The γ_ T approaches a constant value of 2.2 for high σ_ e galaxies, and flattens for lg(σ_ e/ km s^-1)≲2.3, reaching 1.5 for lg(σ_ e/ km s^-1)≈1.8. The total and stellar slopes track each other tightly, with γ_ T≈γ_*-0.174 over the full σ_ e range. This confirms the dominance of stellar matter within R_ e. We also show that there is no perfect conspiracy between baryonic and dark matter, as γ_* and γ_ DM do not vary inversely within the σ_ e range. We find that the central galaxies from TNG50 and TNG100 simulations do not reproduce the observed galaxy mass distribution, which we attribute to the overestimated dark matter fraction, possibly due to a constant IMF and excessive adiabatic contraction effects in the simulations. Finally, we present the stacked dark matter density profiles and show that they are slightly steeper than the pure dark matter simulation prediction of γ_ DM≈1, suggesting moderate adiabatic contraction in the central region of galaxies. Our work demonstrate the power of stellar dynamics modelling for probing the interaction between stellar and dark matter and testing galaxy formation theories.