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Gaia DR2 (along with earlier surveys) has revealed vertical
breathing motions in the Milky Way, with stars on both sides of the
Galactic mid-plane moving coherently towards or away from it. The full
consensus about the driving mechanisms (external and/or internal) for
these breathing motions is still missing till date. In this talk, first
I will discuss the characteristics of such vertical breathing motions
driven by spiral density waves by making use of a high-resolution,
self-consistent simulation of a Milky Way-like galaxy, and how the
amplitudes of the resulting breathing motions vary with stellar
populations of different stellar ages. Further, I will briefly mention
the excitation of breathing motions in case of fly-by encounters in disc
galaxies, using a set of N-body models. Lastly, I will highlight our
findings about the age variation of the vertical breathing motion of the
Milky Way, obtained from the Gaia DR2, and what better understanding can
be achieved with the recent Gaia DR3. |