An added feature is that the objects can be added as if they are in a "galactic" disk with given inclination and position angle. The default is a "face-on" view (inc=0). No corrections for brightness due to inclination are made however.
flat A A exp A.exp(-r/h) A,h gauss A.exp(-r^2/(2h^2)) A,h bar A.exp(-r/h) A,h,e,b (e=1-minor/major b=bar position angle w.r.t. disk) noise gaussian(m,s) mean,sigma spiral A.exp(-r/h) A,h,k,p,m,r0,p0 ferrers A.(1-r^2)^p A,h,e,b,p (h=size of bar, p=power to 1-r^2) isothermal A.(1+r^2)^p A,h,p test x+10y+100z - maybe to be implemented: j1x J1(x)/x comet 2d proj jet jet model w/ power law brightness shell 2d proj of shell poissonA few object that are in MIRIAD’s imgen(1MIRIAD) program and not listed here directly, can be simulated or replaced by:
level same as our flat cluster same as isothermal, except we also allow p different from -0.5 noise notice we have a mean, miriad doesn’t, also miriad has a crude low approximation point use exp with a very small scale length h gaussian our gauss, but bmin/bmaj via inc gauss3 no equivalent, ccdgen does not support 3D models yet disk use ferrers with p=0
Most of these objects have a peak or representative intensity value as the first argument, and a scale length as the second parameter. The next parameters are sometimes scale free
Bars have an additional axis ratio (we mostly use e=1-b/a here) and position angle of the bar w.r.t. the disk in the disk plane (see snaprotate(1NEMO) for an approach if you know the angle of the bar in the sky plane). A Ferrers bar also needs to know the power (usuall an integer) to which 1-r^2 is raised.
Spirals are yet more complex: A and h are the usual peak and exponential scale-length. k is the wavenumber (related to the pitch angle as tan(pitch) =1/(2.pi.k.r), see also mkspiral(1NEMO) ), p controls the relative width of the spiral (assumed to be cos^p(m*phi), r0 the starting radius of the spiral (defaults to 0), p0 the phase of the spiral at radius r0, and m the number of spiral arms. In particular, since the pow(3) function is used internally for non-integer values of p, the behavior of m for integer and non-integer values of p is different: for integer values our own internal powi(3NEMO) is used, and correctly represents. For example, for m=1 and p=1 you’ll get a one armed spiral, but with negative counter-arm. With p=2 it becomes a 2-armed spiral, as they will get progressively narrower as p remains even and gets higher. For odd values of p you will again have a positive and negative spiral, and as p gets larger, the arms get narrower. By making sure p becomes non-integer, e.g. p=2.0001, the negative arm becomes 0.
ccdgen out=- object=exp spar=1,40 pa=60 inc=45 size=256 |\ ccdgen - bar.ccd object=bar spar=10,6,0.5,70 pa=60 inc=45or if you want them to be a bit more astronomical, you’ll need to make the units come out in degrees for the conversion to FITS, viz.:
ccdgen out=- object=exp spar=1,40/3600 pa=60 inc=45 size=256 cdelt=-1/3600,1/3600 |\ ccdgen - - object=bar spar=10,6/3600,0.5,70 pa=60 inc=45 |\ ccdfits - bar.fits radecvel=t
4-Jan-05 V0.1 Created PJT 6-jan-05 V0.7 added (many features and) factor= PJT 8-jan-05 V0.8 add #arms parameter to spiral PJT 31-jan-12 V0.9 added object=test PJT
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