Sandeep Kumar Kataria (Indian Institute of Astrophysics, Bangalore)
We use N-body simulations of bar formation in an isolated galaxy to study the effect of bulge mass and bulge concentration on bar formation and bar pattern speed. Two sets of models are generated, one that has a dense bulge and high surface density disk and a second model that has a less concentrated bulge and a lighter disk. Our simulations of both the models show that there is an upper cut-off in bulge to disk mass ratio Mb/Md above which bars cannot form; the cut-off is smaller for denser bulges( Mb/Md = 0.2) compared to less denser ones (Mb/Md = 0.5). We define a new criterion for bar formation in terms of bulge to disk radial force ratio (Fb/Fd) at the disk scale length above which bars cannot form and show that if Fb/Fd > 0.35, a disk is stable against bar formation. This criterion agrees with the observations of barred galaxies from S4G catalogue.