Seminář ÚTFA: Zdeněk Prudil

Ústav teoretické fyziky a astrofyziky vás zve na přednášu ústavního semináře:

Zdeněk Prudil: Tracing the Galactic Bar with Bulge RR Lyrae Stars

The Galactic bar is a key driver of the Milky Way's internal evolution, redistributing stars and gas, influencing the structure of the central bulge. Understanding how different stellar populations interact with the bar helps unravel the Galaxy's formation history. I analyze the RR Lyrae population toward the Galactic bulge to investigate its spatial and kinematic connection to the bar. RR Lyrae stars, as old, metal-poor standard candles, provide a unique view into the early Galaxy.

By refining reddening maps and extinction laws from visual to near-infrared bands, I derive accurate distances that remove bar-like artefacts caused by extinction law variations. I find that only metal-rich RR Lyrae stars align spatially with the bar, while metal-poor stars form a more spheroidal distribution. For 8456 stars with full kinematics, I compute orbits in a Milky Way-like potential, revealing that prograde motion dominates among metal-rich stars, whereas metal-poor ones exhibit an increase in the retrograde orbits. These retrograde stars have stable orbital frequencies and are highly concentrated toward the Galactic center. Comparisons with N-body+SPH simulations suggest that such a structure can emerge through secular evolution without invoking a classical bulge.