Survey Parameters
The simulations analyzed here are grouped into 11 ensembles, each
containing 8 realizations. One ensemble serves as a reference; the
other 10 ensembles are derived by varying parameters including the
pericentric separation, disk orientations, and disk velocity
dispersion.
The galaxy models used in these experiments have three components:
 Bulge: a Hernquist (1990) model with mass
M_{b} = 0.0625 and scale radius a_{b}
= 0.04168, smoothly truncated beyond a radius r_{t,b}
= 4.0.
 Disk: an exponential/isothermal model with mass
M_{d} = 0.1875 and scale radius R_{d}
= 1/12. The radial velocity dispersion is twice the vertical
velocity dispersion, and the latter is set to make the scale height
constant.
 Halo: a Navarro, Frenk, & White (1996) halo with mass
M_{h} = 1.0 and scale radius a_{h} =
0.2, smoothly truncated beyond a radius r_{t,h} =
0.4474 using the expression in Springel & White (1999).
All simulations have these parameters in common:
 Orbital energy: the galaxies are launched with relative
positions and velocities approximately consistent with a
zeroenergy orbit.
 Particle number: all simulations were run with a total
of N = 65536 bodies.
 Smoothing scale: when calculating forces, the mass
distributions were smoothed by convolution with a Plummer model
with radial scale 0.01 length units.
 Timestep: integrations were performed using a
leapfrog with a step of 1/64 time units.
The reference ensemble has these parameter values:
 Pericentric separation: two point masses launched on
the same initial orbit would reach a minimum separation
r_{p} = 0.2 length units.
 Disk orientation: the disks have inclinations
i_{1} = i_{2} = 0 and pericentric
arguments w_{1} = w_{2} = 0.
 Disk velocity dispersions: the disks have constant
scale height z_{d} = 0.005, implying Q =
1.35 over most radii.
Parameter values for all 11 ensembles are:
Key
 r_{p}
 i
 w
 Q
 Notes

101  0.2  0.0  0.0  1.35  reference 
102     1.9  warm disk 
103     2.7  hot disk 
111   40    modest inclination 
121   40  60  
131   40  60  
141   70    high inclination 
151   70  60  
161   70  60  
201  0.3     wider passage 
301  0.4     widest passage 
Joshua E. Barnes
(barnes@ifa.hawaii.edu)
Last modified: March 2, 2001
http://www.ifa.hawaii.edu/~barnes/research/tidal_dwarfs/survey.html