Next: III. Programmers Guide Up: 5.6 Exchanging data Previous: 5.6.4 Initializing   Contents   Index

## 5.6.5 Galactic Velocity Fields

As an example, a special section is devoted here to the analysis of galactic velocity fields. The following programs are available:

```	ccdvel		create a model velocity field, from scratch
rotcur		tilted ring model velocity field fitting
rotcurshape	annulus rotation curve shape fitting to a velocity field

% set r=\$(B!F(Bnemoinp 0:60\$(B!F(B
% set v=\$(B!F(Bnemoinp 0:60 | tabmath - - "100*%1/(20+%1)" all\$(B!F(B
% ccdvel out=map1.vel rad="\$r" vrot="\$v" pa=30 inc=60
% rotcurshape in=map1.vel radii=0,60 pa=30 inc=60 vsys=0 units=arcsec,1 \
rotcur1=core1,100,20,1,1 tab=-

% ccdmath out=map0.vel fie=0 size=128,128
% rotcurshape map0.vel 0,40 30 45 0 blank=-999 resid=map.vel \
rotcur1=plummer,200,10,0,0 fixed=all units=arcsec,1
```

Since rotcurshape computes a residual velocity field, one can easily create nice model velocity fields from any selected shape by ``fitting'' a rotation curve shape to a velocity field of all 0s and keeping all parameters fixed to the requested values:

```   % ccdmath out=map0.vel fie=0 size=128,128
% rotcurshape map0.vel 0,40 30 45 0 blank=-999 resid=map.vel \
rotcur1=plummer,200,10,0,0 fixed=all units=arcsec,1
% ccdplot map.vel -100:100:10 blankval=0 cmode=1
```

(c) Peter Teuben