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.