D. V. Odynets | Searcharxiv

arXiv2026

Kinematic analysis of the TNG50 Milky Way and Andromeda analogues

We investigate whether Ogorodnikov-Milne (O-M) parameters can serve as kinematic tracers of spiral structure in four Milky Way- and Andromeda-like disc galaxies from the TNG50-1 simulation at z=0. Stellar particles are analysed in disc-aligned reference frames, with velocities referenced to the mass-weighted mean stellar velocity within one stellar half-mass radius. Local O-M fits on a regular grid yield centroid velocities and the components of the velocity-gradient tensor, characterising local deformation and rotation. We compare their spatial distributions with stellar surface-density and relative overdensity maps and examine the influence of parameter uncertainties. The galaxies exhibit diverse coherent kinematic patterns. Features selected using the generalised Oort constants A, B, and C+K display partial correspondence with stellar overdensities, depending on the galaxy and the adopted centroid-selection criteria. For TNG50-456326, a galaxy-specific selection enables us to fit four logarithmic spiral branches and determine their geometrical parameters. Their morphology suggests two principal arms and two secondary branches. We compare the fitted spirals with stellar- and gas-mass overdensity and radial velocity maps and examine the spatial relationship between the identified stellar structures and the gas distribution. Qualitative similarities to the morphology and kinematic patterns of the Milky Way make TNG50-456326 a promising candidate for further investigation as a kinematic analogue. Our results support the use of local O-M parameters as complementary diagnostics of non-axisymmetric disc structure, while highlighting the need for galaxy-specific selection criteria.

astro-ph.GA↗

arXiv2026

The solar Galactocentric distance and local kinematic parameters from Gaia DR3 using Bottlinger's equations

The solar Galactocentric distance, $R_0$, together with the local kinematic parameters of the Milky Way, provides fundamental constraints on the Galactic structure and rotation. Their accurate determination has become possible with the hight astrometric precision of Gaia DR3 catalogue. We determine the Galactocentric distance, the Solar peculiar motion components $(u_0,v_0,w_0)$, and the local angular velocity of Galactic rotation, $ω_0$, using a self-consistent approach based on Bottlinger's equations within a nonlinear least-squares framework. Bottlinger's equations were applied to approximately 13 million luminous giant stars $(M_G<4)$ selected from Gaia DR3. The analysis was carried out for two subsamples: a thin disk dominated sample (|z|<0.5 kpc) and a mixed thin and thick disk sample (|z|<1.0 kpc). The kinematic parameters were estimated using a nonlinear generalized least-squares method. We obtained $R_0=8.165\pm0.024$kpc and a local angular velocity of Galactic rotation $ω_0=28.477\pm0.002$ km/s/kpc for the thin disk dominated sample. The Solar peculiar motion components are $(u_0,v_0,w_0)=(9.261\pm0.006,16.593\pm0.008,7.686\pm0.008)$km/s. Including mixed thin and thick disk stars resulted in a systematic shift in $R_0$, yielding $R_0=8.333\pm0.022$kpc, while the Solar peculiar motion and local angular velocity remain consistent within uncertainties. The Galactic kinematic parameters derived are consistent with recent independent determinations. The Solar peculiar motion parameters and the local angular velocity remain stable for different vertical selections, the recovered Galactocentric distance exhibits a systematic dependence on the adopted stellar sample, indicating that the vertical structure of the tracer population should be taken into account when determining $R_0$.

astro-ph.GA↗