```
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-

```

## 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-
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
box box-number

```

```       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)
```

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