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Kinematic Structure of the Milky Way Galaxy, Near the Spiral Arm Tangents

Vallée, Jacques P.

We compare the observed radial velocity of different arm tracers, taken near the tangent to a spiral arm. A slight difference is predicted by the density wave theory, given the shock predicted at the entrance to the inner spiral arm. In many of these spiral arms, the observed velocity offset confirms the prediction of the density wave theory (with…

Arm Tangents and the Spiral Structure of the Milky Way—The Age Gradient

Vallée, Jacques P.

From the Sun, a look at the edge of each spiral arm in our Milky Way (seen tangentially, along the line of sight) can yield numerous insights. Using different arm tracers (dust, masers, synchrotron emission, CO gas, open star clusters), we observe here for the first time an age gradient (about 12 +/-2 Myrs/kpc), much as predicted by the density wa…

Standard and Truncated Luminosity Functions for Stars in the Gaia Era

Zaninetti, Lorenzo

The luminosity function (LF) for stars is here fitted by a Schechter function and by a Gamma probability density function. The dependence of the number of stars on the distance, both in the low and high luminosity regions, requires the inclusion of a lower and upper boundary in the Schechter and Gamma LFs. Three astrophysical applications for star…