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

Abstract

ABSTRACT 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 $10^9\ {\rm {\rm M}_{\odot }}\lesssim M_*\lesssim 10^{12}\ {\rm {\rm M}_{\odot }}$, including both early-type and late-type galaxies. We use the mass-weighted density slopes for the stellar $\overline{\gamma }_*$, dark $\overline{\gamma }_{_{\rm DM}}$ and total $\overline{\gamma }_{_{\rm T}}$ mass from the MaNGA DynPop project. As previously reported, $\overline{\gamma }_{_{\rm T}}$ approaches a constant value of $\overline{\gamma }_{_{\rm T}}\approx 2.2$ for high σe galaxies, and flattens for $\lg (\sigma _{\rm e}/{\rm km\ s^{-1}})\lesssim 2.3$ galaxies, reaching $\overline{\gamma }_{_{\rm T}}\approx 1.5$ for $\lg (\sigma _{\rm e}/{\rm km\ s^{-1}})\approx 1.8$. We find that total and stellar slopes track each other tightly, with $\overline{\gamma }_{_{\rm T}}\approx \overline{\gamma }_*-0.174$ over the full σe range. This confirms the dominance of stellar matter within Re. We also show that there is no perfect conspiracy between baryonic and dark matter, as $\overline{\gamma }_*$ and $\overline{\gamma }_{_{\rm DM}}$ do not vary inversely within the σe 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 $\overline{\gamma }_{_{\rm DM}}\approx 1$, suggesting moderate adiabatic contraction in the central region of galaxies. Our work demonstrates the power of stellar dynamics modelling for probing the interaction between stellar and dark matter and testing galaxy formation theories.