makimg


 MAKIMG -- make a starting image for doppler tomography or for simulating
           data.

 Parameters:

   NSIDE     -- Size of images (which are square)

   NIMAGE    -- Number of images. Blended lines can be dealt with by 
                assigning an image for each line. It is also possible 
                for the same image (bar a scaling factor) to represent 
                more than one line.

   IMAGE     -- The name of the image file to create 

   VPIX      -- Size of pixels in km/s. The product of NPIX and VPIX should
                more than cover the width of the line of interest. VPIX should
                be less than or equal to the km/s/pixel of the data. Note 
                there is no problem if VPIX is much smaller, except in the 
                extra CPU and memory required. If you have blended lines
                the images need only extend over each line, not the whole
                blend.

   NWAVE     -- Number of lines. e.g you could map the Paschen series and 
                the CaII triplet with 2 images, one for CaII and one for the
                hydrogen lines, but you would have to specify a wavelength for
                each line to be mapped. NWAVE >= NIMAGE

   WAVE(NWAVE) -- Central wavelength of each line in Angstroms

   If (NWAVE .NE. NIMAGE)

     NWHICH(NWAVE) -- Defines which image corresponds to each line. e.g.
                      If you had two image accounting for three lines
                      you might set NWHICH = 1,2,2 which means that the
                      first image corresponds to the first wavelength while
                      the second image corresponds to the other 2 lines.

     SCALE(NWAVE)  -- Defines scale factor to apply to each line (allows for
                      different lines to have same image but a different
                      scaling.) These values can be optimised outside MEM
                      using optscl. e.g. on the above example you might
                      have SCALE = 1.,1.,0.5

   FWHM      -- Full width half maximum of instrument, km/s. Don't make too 
                large or it will be attempting an impossible deconvolution.
                Too small does not matter in this respect, but a finite 
                FWHM is good for smoothing out numerical noise.

   GAMMA     -- Systemic velocity of system km/s.

   NSUB      -- Subdivision factor to account for phase smearing from finite 
                exposure length. Each exposure will be divided into NSUB 
                exposures uniformly spread through the exposure and then 
                trapezoidally averaged. If your exposures are short compared 
                to the orbital period, set = 1. If you do use it, only
                apply towards the end of the iterations because it slows 
                things down (by a factor NSUB).

   OFFSET    -- Constant to add to all phases to account for zero point
                error in the ephemeris. This rotates the entire image but
                the image must be re-iterated after any change to OFFSET
                for this to be seen.

   NDIV      -- The projections of model to data is done first onto a
                fine grid which is then blurred and binned onto the data 
                array. This is usually faster than blurring each pixel 
                directly onto the coarse grid. NDIV is the factor by 
                which each data pixel is split to give the fine array. 
                NDIV must be large enough so that the FWHM is well 
                sampled. e.g if FWHM=2, then NDIV>2 should be used.

                There is no reason not to change NDIV as you iterate
                and you could for example start with NDIV = 1 and only raise
                it for the final few iterations. Note that large NDIV values
                will slow things down so be careful.
                (Use 'setobj 5 image.more.doppler.ndiv' to set ndiv = 5 for
                 example)

   USE       -- This specifies whether the HJDs or phases should be used
                to compute the phases during iterations. The option of
                HJDs is provided to allow one to account for changes in the
                ephemeris, however the method of choice should normally be
                'phases'. The reason is that if the data comes from a
                phase-folding operation (pbin inside molly) while the
                phases are correct, the HJDs are not. e.g. say you average
                two spectra at phase 0.5 but 1 cycle apart. The HJD will be
                set half-way between i.e. phase 0!. The phase on the other
                hand is correctly dealt with. You will be OK with either
                option if you are dealing with straight spectra.

                The two options are:

                   HJDs   -- use HJDs
                   Phases -- use phases

                and you can change them by editing the NDF with setobj.


 Now parameters defining shape of image:
 
   FANCY     -- .FALSE. you just get a constant image. .TRUE. then you 
                are prompted for many more parameters to define a gaussian
                spot, a spiral pattern and a power law in radius.            

   If(FANCY)

     XCEN      -- X centre of gaussian spot (km/s)
     YCEN      -- Y centre of gaussian spot (km/s)
     WIDTH     -- FWHM of gaussian spot (km/s)
     PGAUSS    -- Peak intensity of gaussian
     XSP       -- X centre of spiral pattern and power law disc (km/s)
     YSP       -- Y centre of spiral pattern and power law disc (km/s)
     VLOW      -- Lowest disc velocity (outer disc) (km/s)
     VHIGH     -- Highest disk velocity (inner disc) (km/s)
     EXPON     -- exponent between them (intensity scales as V**EXPON)
     ANGLE     -- Opening angle of two armed spiral pattern (degrees)
     CURVE     -- Difference in angle between outer and inner velocities
     PPOWER    -- Peak intensity of power law background
     PSPIRAL   -- Peak intensity of spiral shock


  Else

     CONST     -- Constant per pixel

 Don't worry about the levels you set; these can be tweaked with optscl.

This command belongs to the class: essential


Tom Marsh, Warwick