[Almasci] Re: [mmaimcal]Re: Comment in ALMA memo 489

[Stephane Guilloteau]

    Mark writes:
>
> Long ago, when I was but a child, people used something called "Clean
> Boxes" to restrict the model brightness distribution.  But now that I am
> grown, the algorithms have grown up too, and (at least in some
> packages), you can provide an arbitrary mask image to function as
> the "clean box".  That mask image can restrict clean components to
> be within the generalized primary beam pattern for the mosaic.
>
>    -M
>
>
    Even I was a child in these days...

    The arbitrary mask is used in all modern CLEAN tools as far as I know. Yet, it still have the undesirable property
of sharp edges. It's not an issue if the "clean area" goes beyond the primary beam, but it does not help at all imposing
more constraints on the large scale shape of the brightness distribution within this area.

    Perhaps a probabilistic approach (using the primary beam shape as a likelihood indicator on the location of the next
Clean component) would help. Something similar to simulated annealing could be used in searching for Clean components.

        Stephane