MOMENTS(1)                TIPSY COMMANDS               MOMENTS(1)

NAME

       moments - write the shape as a funtion of radius

SYNOPSIS

       moments box-number center-box-number particle binning bin-
       number filename minimum_radius

DESCRIPTION

       moments is a command that produces a file of  name,  file-
       name,  that  contains  various  physical  parameters  that
       relate to the shape and orientation of the density distri-
       bution  for particles of type particle in box, box-number.
       If the  boxes  box-number  or  center-box-number  are  not
       loaded an error is generated.  The shapes and orientations
       are calculated using the iterative technique described  in
       Katz  (Ap.J.  368:325,  1991).   The initial guess for the
       center of the density distribution is taken to be the cen-
       ter  of  mass of box center-box-number.  The binning argu-
       ment refers to how the particles are binned,  either  lin-
       early  or  log in radius.  There are bin-number equal size
       bins distributed equally in radius or log  radius  between
       minimum_radius and the size of box box-number depending on
       the binning argument.  The output file has  the  following
       columns:  radius, b/a, c/a, phi, theta, psi, center-x,cen-
       ter-y,and center-z where b/a refers to the  ratio  between
       the  intermediate axis and the long axis and c/a refers to
       the ratio between the short and long axes.  Phi, theta and
       psi  refer  to the Euler angles that describe the orienta-
       tion of the density distribution.

OPTIONS

   Particle
       The possible choices for particle are:

              all
                 Use the all the particles in box box-number

              dark
                 Use only the dark matter particles in  box  box-
                 number

              gas
                 Use only the gas particles in box box-number

              star
                 Use only the star particles in box box-number

   Binning
       The possible choices for binning are:

              lin
                 Make  bin-number  bins  spaced equally in radius
                 between minimum-radius and the size of box  box-
                 number

              log
                 Make  bin-number  bins  spaced  equally  in  log
                 radius between minimum-radius and  the  size  of
                 box box-number

SEE ALSO

       profile(1), rotationcurve(1),

BUGS

       The  technique doesn't always converge, particularily when
       the density distribution is very clumpy.  Things  converge
       much  better  when  the box center-box-number contains the
       true center for the density distribution in box box-number
       and is as small as possible.



KQ Release 2.0            22 MARCH 1994                MOMENTS(1)