2022MNRAS.514.3329M

Gas discs of late-type galaxies are flared, with scale heights increasing with the distance from the galaxy centres and often reaching kpc scales. We study the effects of gas disc flaring on the recovered dark matter halo parameters from rotation curve decomposition. For this, we carefully select a sample of 32 dwarf and spiral galaxies with high-quality neutral gas, molecular gas, and stellar mass profiles, robust H I rotation curves obtained via 3D kinematic modelling, and reliable bulge-disc decomposition. By assuming vertical hydrostatic equilibrium, we derive the scale heights of the atomic and molecular gas discs and fit dark matter haloes to the rotation curves self-consistently. We find that the effect of the gas flaring in the rotation curve decomposition can play an important role only for the smallest, gas-dominated dwarfs, while for most of the galaxies, the effect is minor and can be ignored. We revisit the stellar- and baryon-to-halo mass relations (M_*-M₂₀₀ and M_bar-M₂₀₀). Both relations increase smoothly up to M₂₀₀ ~10¹² M_☉, with galaxies at this end having high M_*/M₂₀₀ and M_bar/M₂₀₀ ratios approaching the cosmological baryon fraction. At higher M₂₀₀, the relations show a larger scatter. Most haloes of our galaxy sample closely follow the concentration-mass (c₂₀₀-M₂₀₀) relation resulting from N-body cosmological simulations. Interestingly, the galaxies deviating above and below the relation have the highest and lowest stellar and baryon factions, respectively, which suggests that the departures from the c₂₀₀-M₂₀₀ law are regulated by adiabatic contraction and an increasing importance of feedback.