Program: VELFI
Purpose: Calculates model velocity field from input parameters
given by the user.
Category: MODELS, ROTATION-CURVES, VELOCITY-FIELDS
File: velfi.c
Author: K.G. Begeman
Keywords:
INSET= Set (and subset) of original velocity field needed to
create the output set.
OUTSET= Set (and subset) of the model velocity field.
RADII= Radii (in arcsec) at which the rotation curve is
measured. Up to 256 radii can be specified.
PA= Position angle of major axis (in degrees) for the radii
entered above.
INCL= Inclination angle (in degrees) for the radii entered above.
VROT= Rotational velocities (in km/s) for the radii entered
above.
VRAD= Expansion velocities (in km/s) for the radii entered
above.
VSYS= Systemic velocity (in km/s) for the radii entered above.
POS= The rotation centre.
Notes: 1) The program calculates the model velocity field from
the formula :
V(X,Y)=VSYS+VROT(R)*COS(T)*SIN(INCL)+VRAD(R)*SIN(T)*SIN(INCL)
where: V is resulting velocity field
VSYS systemic velocity
VROT rotational velocity (rotation curve)
T azimuthal angle (in galaxy plane)
INCL inclination
VRAD expansion velocity
R radius
X, Y grid coordinates
2) For the keywords PA=, INCL=, VROT=, VRAD= and VSYS=
you can enter less values than the number of rings you have
specified; in that case these quantities are taken to be
constant for the remaining number of rings at a value
equal to the last one given.
The keywords RADII=, PA=, INCL=, VROT=, VRAD= and VSYS=
are repeated until you answer with carriage return. This
makes it possible to enter recall files. Note that the
macro is only saved when you enter a recall file with last
line empty. You can also enter more than one value to
these keywords.
Updates: May 21, 1982: KGB, original document created.
Feb 26, 1983: KGB, program inplemented.
May 7, 1986: KGB, migrated to VAX-VMS.
Apr 12, 1988: KGB, new document.
Dec 11, 1989: KGB, more than one systemic velocity.
Jul 27, 1992: KGB, Converted to C and Unix.