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mkexphot - make an exponential disk (hot) embedded in a halo


mkexphot out=out_file [parameter=value] ...


mkexphot makes an N-body realization of a hot exponential disk. It lives inside an assumed dark halo. To evolve such a model the halo has to be made seperately and added to the output snapshot, or an N-body integrator which can handle a fixed external analytical potential, like hackcode3, must be used.

The input file is an ASCII table, consisting of two lines with header information, and for each radius local information of the disk and halo. It is described in more detail below.


The following parameters are recognized.
Table with as a function of radius the density, various radial forces and velocity dispersions. If in_table is not found in the current working directory, the directory $NEMO/data is also searched [No default].
The exponential disk is written to out_file in snapshot(5NEMO) format. [No default]
Optional input snapshot file. If provided, the particles in this file are used to define the positions. The keyword nbody is then not used, but taken from this input file. [default: not-used].
Number of particles for the disk. Only used when test_file not provided. [Default: 1024].
Inner cutoff radius of disk. [Default: 0.0].
Outer cutoff radius of disk. [Default: 25.0].
Ratio used to convert vertical velocity dispersion into radial velocity dispersion. [Default: 2???].
Scalelenght used in conversion from vertical velocity dispersion into radial velocity dispersion [Default: 1???].
Random number seed. [Default: 0.]
Additional random verbiage headline for output file. [Default: none.]
Force a different mass fraction of halo to disk. This is not recommended, since the proper value is taken from the input table. A different value will most likely not produce a well behaved disk. [default: not used]

Table Format

The table is plain ASCII. First two lines are header information, followed by a table of information for each radius.
  nrad, rout, h, z0, dens0
  vhmax, rhcore, q2i, dkmass, hamass
  radius, densit, frdis0, frhal0, frtot0, frdis2, frhal2, frtot2,
         vdisk, vhalo, vrot, sigmad, sigmah, sigmaz

The first line contains information for the exponential disk: nrad = number of radii in table, rout = outer radius, h = disk scale-lenght, z0 = disk vertical scaleheight, and dens0 = central disk density.

The second line contains information for the halo: vhmax = maximum halo velocity, rhcore = halo core radius, q2i = halo flattening parameter, dkmass = disk mass (actually redundant), and hamass = the halo mass.

The q2i parameter is currently not used.

All subsequent nrad lines contain: the radius, density, radial force of disk, halo and sum, second radial force of disk, halo and sum, rotational velocity of disk, halo and sum and finally the velocity dispersion in disk, halo and z. See code for more details.

See Also

mkexpdisk(1NEMO) , mkkd95.c(1NEMO)

N-Body realizations of compound galaxies, Hernquist, L. (ApJ Suppl, 86:389-400, 1993 June)


src/nbody/init    mkexphot.c
dat               expmodel.inp (example input table)


Stefano Casertano (Fortran version), Peter Teuben (C version)


xx-xxx-8x    Created in the Dark Ages            Stefano
xx-sep-90    Adapted for Nemo, converted into C    PJT/RAG
23-oct-90    Fake different halo/disk ratio       PJT
22-jul-91    doc improvements - formalized IMSL interface    PJT

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