The inner mass distribution of late-type spiral galaxies from SAURON stellar kinematic maps

We infer the central mass distributions within 0.4-1.2 disc scale lengths of 18 late-type spiral galaxies using two different dynamical modelling approaches

• the Asymmetric Drift Correction (ADC) and axisymmetric Jeans Anisotropic Multi-gaussian expansion (JAM) model. ADC adopts a thin disc assumption, whereas JAM does a full line-of-sight velocity integration. We use stellar kinematics maps obtained with the integral-field spectrograph SAURON to derive the corresponding circular velocity curves from the two models. To find their best-fit values, we apply Markov Chain Monte Carlo (MCMC) method. ADC and JAM modelling approaches are consistent within 5% uncertainty when the ordered motions are significant comparable to the random motions, i.e, $\overline{v_{\varphi }}\mathrm{/}{\sigma }_R$ is locally greater than 1.5. Below this value, the ratio $v_{\mathrm{c},\mathrm{J}\mathrm{A}\mathrm{M}}\mathrm{/}{v}_{\mathrm{c},\mathrm{A}\mathrm{D}\mathrm{C}}$ gradually increases with decreasing $\overline{v_{\varphi }}\mathrm{/}{\sigma }_R$, reaching $v_$\mathrm{c},\mathrm{J}\mathrm{A}\mathrm{M}$\approx 2 \times v_$\mathrm{c},\mathrm{A}\mathrm{D}\mathrm{C}$$. Such conditions indicate that the stellar masses of the galaxies in our sample are not confined to their disk planes and likely have a non-negligible contribution from their bulges and thick disks.