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mkh41 - Create a Holmberg 1941 disk
mkh41 creates a disk of particles similar to the one used in
Holmberg’s 1941 paper (1941ApJ....94..385H). Currently each ring is placed in a
separate snapshot. Use snapmerge(1NEMO)
if they must be in a single snapshot.
The disk is rotating counter clock wise by default, but with totally fake
velocities. See the example below to assign more realistic velocities.
disk quoted in the 1941 paper has a mass of 10^11 solar masses, and a diameter
of 2300 pc.
The following parameters are recognized in any order
if the keyword is also given:
It is hard to create the exact same initial conditions
as in the H41 paper, as not enough details are provided. Also, Figure 4a/b
seem to suggest that the inner 7 points are not even acted upon self consistently,
but just following the path of the galaxy.
- output file name, each ring will be
in a separate snapshot(5NEMO)
. Use snapmerge(1NEMO)
to merge the rings into
a single snapshot. No Default.
- number of particles for each ring. [Default:
- radii of rings. The number of rings must match that
of nbody=. [Default: 0,1,2,3,4]
- Mass of a particle in each ring. The
number of rings must match that of nbody=. [Default: 1.0,1.0,1.0,0.7,0.3]
- The position angle of the first particle in each ring, 0 being along the
Y axis to match the H41 disk as shown in Fig 3b. The number of rings must
match that of nbody=. [Default: 0,0,0,0,0]
- Sign of the angular
momentum. 1 means counter clockwise rotation. [Default: 1].
for output 
A set of French Curves is not
used for this program.
Since this program does not properly compute
rotational velocities, and because each ring is in a separate snapshot,
it is somewhat cumbersome to create the actual initial conditions for a
true Holmberg 1941 disk:
mkh41 - |
snapmerge - - |
snapcenter - - m |
hackforce - - tol=0.001 fcells=2 |
snapdisk - h41.in
mkconfig(1NEMO), mktt72(1NEMO), mkdisk(1NEMO), snapscale(1NEMO), snapstack(1NEMO)
Holmberg, E. (1941) - On the clustering tendencies among the nebulae. ApJ.
Lindblad, P.O. (1960) - The development of spiral structure in a galaxy approached
by numerical computations
Peter Teuben, Alar Toomre
15-Jul-2009 V1.0 Created at PiTP (IAS @ Princeton) PJT + AT
22-jul-2009 V1.1 added sign= PJT
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