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.