The unprecedented astrometric data provided by the European Space Agency’s Gaia mission has opened a new era in the study of the Milky Way. By measuring the positions and velocities of millions of stars in six-dimensional phase space, Gaia offers a unique opportunity to investigate the dynamical state of our Galaxy and to test fundamental assumptions about its structure and evolution.
My research has focused on extending and analyzing Gaia kinematic maps far beyond the regions originally explored by the Gaia Collaboration. By applying statistical deconvolution techniques to correct for parallax uncertainties, we reconstructed stellar velocity fields out to galactocentric distances of approximately 20 kpc. These extended maps reveal that the Milky Way is not a simple stationary system in rotational equilibrium. Instead, it exhibits large-scale streaming motions, significant velocity gradients, and complex kinematic patterns in all velocity components.
These findings suggest that the Galaxy is dynamically more complex than commonly assumed and may be influenced by a combination of internal structures, external perturbations, and departures from equilibrium. To interpret these observations, we have investigated a variety of dynamical scenarios, including modified gravity models, dark matter-based models, and departures from the standard Jeans equilibrium framework.
More recently, I have developed new methods to reconstruct the two-dimensional velocity fields of external galaxies from spectroscopic observations. Traditional analyses generally assume axisymmetry and focus on rotation curves. Our approach allows the measurement of both radial and tangential velocity components and their angular variations, providing a more complete description of galactic dynamics.
Applying these techniques to nearby spiral galaxies has revealed that non-circular motions are widespread and often associated with bars, spiral structures, warps, asymmetries, and environmental interactions. By reconstructing spatially resolved velocity fields, these methods provide new tools for studying the dynamical state of galaxies and for testing competing models of galaxy formation, dark matter, and gravity.
More broadly, this research seeks to understand how galaxies evolve as dynamical systems and how their observed motions can be used to constrain the distribution of visible and dark matter, the validity of equilibrium assumptions, and the physical mechanisms that shape galactic structure.
Francesco sylos labini 