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Basic Information on velmodel
Task: velmodel
Purpose: Make a model image for a theoretical velocity pattern.
Categories: image analysis
VELMODEL generates a MIRIAD image for a theoretical velocity
pattern specified by model input paramaters. The default option
is to make an image of the line-of-sight velocity corresponding
to a rotating disk model:
velocity = vsys +
(vrot*cos(theta-pa)+vrad*sin(theta-pa))*sin(incline)
The output image can be combined with an intensity
image to make a 3D model using the task VELIMAGE.
Key: in
Input image name used as template for the output image.
Key: region
Region of image to be used. The default region is the entire image.
See documentation of region for details. All pixels within the
bounding box are used; pixel masking is ignored.
Key: center
The rotation center in arcsec from the center pixel, measured
in the directions of RA and DEC. Default=0,0.
Key: pa
Position angle of the major axis in degrees. Default is 0. (north).
Key: incline
Inclination angle of the disk in degrees. Default is 0. (face on).
Key: radius
Sample points along major axis in arcsecs. Need not be evenly spaced.
At least one point must be given.
Key: vrot
Rotation curve in the plane of the disk specified by a power law:
rotation velocity = vrot(1)*(r/radius(1))**vrot(2)
At least one point must be given. For options=sample, vrot gives the
rotation velocity sampled at the radius points above, and is
interpolated between the sample points, with zero velocity at zero
radius, and not extrapolated beyond the last point. Units are km/s.
Key: vrad
Radial velocity in plane of disk specified by a power law:
radial velocity = vrad(1)*(r/radius(1))**vrad(2)
Default=0,0. If only one value given then vrad = vrad(1)
Units are km/s.
Key: vsys
Systemic velocity of the disk. Units are km/s. Default=0.
For options=rms, vsys is a constant rms along the line of sight.
Key: z
Thickness of disk, and power law: z' = z(1)*(r/radius(1))**z(2)
Default=0,0. If only one value given then z' = z(1)
The units of z(1) are the same as arcsec along major axis of disk.
Key: out
The output image. No default.
Key: options
rms The output image is the rms calculated from vsys and
the rms velocity along the line of sight, computed by
integrating through the disk thickness given by z.
sample The rotation velocity is specified by values vrot
sampled at the radius values. Default is power law.