Mirroring the image of the Milky Way bar

Abstract

The bar pattern speed (Ωp) is a crucial parameter for understanding dynamics of spiral galaxies, which includes our own Milky Way. Measuring the pattern speed of the Milky Way bar is made difficult by observational limitations, such as dust obscuration in the Galactic plane and incomplete coverage of the far side of the bar. This study investigates whether mirroring the near side of the bar and measuring the pattern speed can yield reliable Ωp estimates using N-body simulations of a barred galaxy. Mock observational samples are generated, incorporating distance uncertainties and cutting out the zone of avoidance. Our results show that mirroring produces reasonable Ωp estimates when distance errors are low but suffers from biases at higher uncertainties. The size of the bar region used for measurements also affects accuracy, improving with bar evolution. While promising, the method requires refinement, such as fixing bar region boundaries and implementing realistic selection functions, to ensure robust application to real Milky Way data. Further tests on diverse simulations are recommended