Gravitational microlensing as a test of a finite-width disk model of the Galaxy

The aim of this work is to show, in the framework of a simple finite-width disk model, that the amount of mass seen through gravitational microlensing measurements in the region $0<R<R0$ is consistent with the dynamical mass ascertained from Galaxy rotation after subtracting gas contribution. Since microlensing only detects compact objects, this result suggests that a non-baryonic mass component may be negligible in this region.Comment: 10 pages, 12 figure

The influence of the velocity dispersion on the velocity-density relation in the disk model of the galaxy

Taking the velocity dispersion term into account in the Jeans equation describing the disk model, counterintuitively allows to reduce the local mass-to-light ratio at the outskirts of flattened galaxies, and stop the unbound growth of mass function. This is possible thanks to a more intertwined relation between the gravitational potential and the rotation curve than for spheroidal systems. This effect is illustrated on the example of galaxy UGC 6446 by finding iteratively the column mass density from the rotation curve supplemented with an isotropic velocity dispersion profile in the disk plane. Along with galactic magnetic fields, this effect would allow to reduce the local mass-to-light ratio at the galactic outskirts

Spiral arm kinematics for Milky Way stellar populations

We present a new theoretical population synthesis model (the Galaxy model) to examine and deal with large amounts of data from surveys of the Milky Way and to decipher the present and past structure and history of our own Galaxy. We assume the Galaxy to consist of a superposition of many composite stellar populations belonging to the thin and thick discs, the stellar halo and the bulge, and to be surrounded by a single dark matter halo component. A global model for the Milky Way's gravitational potential is built up self-consistently with the density profiles from the Poisson equation. In turn, these density profiles are used to generate synthetic probability distribution functions (PDFs) for the distribution of stars in colour- magnitude diagrams (CMDs). Finally, the gravitational potential is used to constrain the stellar kinematics by means of the moment method on a (perturbed)-distribution function. Spiral arms perturb the axisymmetric disc distribution functions in the linear response framework of density-wave theory where we present an analytical formula of the so-called 'reduction factor' using hypergeometric functions. Finally, we consider an analytical non-axisymmetric model of extinction and an algorithm based on the concept of probability distribution function to handle CMDs with a large number of stars. A genetic algorithm is presented to investigate both the photometric and kinematic parameter space. This galaxy model represents the natural framework to reconstruct the structure of the Milky Way from the heterogeneous data set of surveys such as Gaia-ESO, SEGUE, APOGEE2, RAVE and the Gaia mission

Mass distribution in flattened galaxies

It is shown that mass distribution of baryonic matter accounts for the rotation curve of galaxy NGC 4736