Model & Methodology

We model the satellite merger scenario through hydrodynamical Gadget-2 simulations, using a rotating bar potential from Zhao et al. 1994

where (r, θ, φ) are the spherical coordinates fixed in the bar,

and

Based on recent simulations on the inner kiloparsecs region (Kim et al. 2011) we used the following parameters: α = 1.75, b20 = 0.3, b22 = 0.1, ρ0 = 40 Msun pc^−3, r0 = 100 pc. The bar is rotating with a pattern speed of 63 km /s kpc . Given a bar axis ratio of [1 : 0.74 : 0.65], an X1 − X2 transition at r ∼ 200 pc, inner Lindblad Resonance 660 pc and a corotation radius of 2.8 kpc. Enclosed mass inside 200 pc is 1e9 Msun.

The gas in the CMZ is more especifically a cold torus centered on the 180 pc, and extended radially from 130 pc to 230 pc (Launhardt et al. 2002). From Ferrière et al. 2007, the space-averaged density of hydrogen in the torus can be approximated by

 

 with L~55pc and H~29pc.

Periodic and non self-intersecting orbits of the CMZ gas in the x-y plane were  obtained through the shooting technique, integrating the equations of motion with a fourth order Runge-Kutta method.

Our fiducial model consist in around 300.000 particles, with T=1000K. Gas particles where simulated without satellite for 20 Myr in order to get a hydrodynamically relaxed distribution of particles.  Satellite orbit considers dynamical friction.