Lunch talk on Jan. 8, 2024

Comparison of Two Formation Mechanisms of Barred Spiral Galaxies

Speaker: Yirui Zheng (SJTU)

Venue: SWIFAR Building 2111

Time: 12:30 PM, Monday, Jan. 8, 2024

Abstract: 

Galaxy bars can form via internal instability or tidal perturbations by other galaxies. We quantitatively compare the properties of bars formed through the two mechanisms with a series of N-body simulations that form bars under both internal and external mechanisms. In isolated simulations, the galaxy models are set up with different thicknesses, velocity dispersion, different bulge fractions and sizes. In tidal interaction scenarios, we set the galaxy to interact with a perturber of different mass ratios on flyby orbits with different pericenter distances. We will show how the galaxy properties affect the bar formation and how tidal perturbation promotes it. Though tidally induced bars grow faster, their strength and pattern speed are similar to the bars forming in the same disk in isolation. Fourier analysis shows that bars under both mechanisms 1) reach the similar maxima A2 value; 2) fall onto the same $\Omega_p-A_2$ relation; 3) have a similar ratio of the co-rotation radius to the bar length( ${\cal R}=\frac{R_{CR}}{R_{bar}}$). Dynamical analysis shows that the inner stellar disk loses the same amount of angular momentum regardless of the presentation of perturbation, which probably explains the similarity between the tidal and spontaneous bars. I will also show the preliminary results on the comparison of the growth timescale of bars under internal and external mechanisms, as well as the dynamical properties that can potentially used to distinguish tidally induced bars and spontaneous ones.

Report PPT:  SWIFAR_Yirui Zheng.pptx