Basic Information on contsub

Task: contsub
Purpose: Subtract continuum from a datacube
Categories: map manipulation

        CONTSUB is used to subtract the continuum from a datacube which
        can be arbitrarily oriented.  Several subtraction algorithms are
        possible, selected using the mode keyword.  The maximum length
        of the spectral axis is 8192 pixels.
 

Key: in
        Standard keyword in. See the help on in for more information.
 

Key: region
        Standard keyword region. See the help on region for more information.
        Anything outside the region is untouched (only rectangular boxes
        are recognized by contsub).
 

Key: out
        Standard keyword out. See the help on out for more information.
        For modes poly, mean and avgs either this keyword or cont= must
        be specified, for mode subtr it must always be given.  This
        output dataset will contain only those channels from the input
        dataset selected by the 'region' keyword.
 

Key: cont
        An optional output dataset which will be one plane deep and
        contain the continuum map.  For mode=
          poly: the interpolated map at the channel halfway between the
                first and last line channel selected.
          mean: the averaged image that was subtracted from the channel
                maps.
          avgs: the average of the two average images that are
                calculated (see description of mode keyword).
          subtr: an input set which will be subtracted from each plane
                of the input dataset.
        For modes poly, mean and avgs either this keyword or out= must
        be specified, while for mode subtr it must always be given.
 

Key: contchan
        Select channels that supposedly contain continuum signal only.
        A selection is a list of ranges.  A range is specified as
        (z1,z2), meaning channels z1 through z2, or as (z3) for a single
        channel.  Ranges are separated by commas, e.g.
        (z1,z2),(z3),(z4,z5).
 
        For options 'poly' (or 'mean'), the fit (or average), is done
        using all selected continuum channels.  For option 'avgs', the
        selection of continuum channels must consist of two ranges.
        The 'contchan' keyword always refers to spectral channels,
        independent of whether the spectral axis is the 'z'-axis, the
        'x'-axis or any other axis.
        (Not used for mode='subtr').
 

Key: mode
        Selects the continuum-determination algorithm.  In each case the
        operation is done separately for each image pixel.  May be
        abbreviated.  The default is 'poly,1'.
 
        'poly,#' - a polynomial fit of order # is made through the
        selected continuum channels.  The interpolated continuum
        intensity is subtracted from each separate channels.  The
        maximum order is 8.
 
        'mean' - the average intensity of the selected continuum
        channels is calculated and the average is subtracted from each
        channel (equivalent to 'poly,0').
 
        'avgs' - an average of the first range and of the second range
        of channels is calculated and a linear interpolation between the
        two averages is subtracted from each channel.
 
        'subtr' - at each position, subtract the value in the dataset
        given by cont= from the profile at the same position in the
        input dataset.
 

Key: options
        Select which output to write with the cont keyword.  By default
        the continuum is written.  If options=coeff,# one of the
        coefficients of the polynomial fit is written instead.
        '#' gives the order for which the coefficient is written (e.g.
        if cont=a+bx: 0='a', 1='b', etc).
 

Key: verbose
        verbose=true makes contsub print out some info every now and
        then.
 

Key: velaxis
        For datacubes where the spectral axis cannot be determined
        automatically, this may be used to indicate which it is.  Must
        be one of 'x', 'y', 'z', 'a', 'b', 'c', or 'd'.
        The default is 'z'.
 
Revision: 1.5, 2012/03/13 02:21:33 UTC