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<allpages gapfrom="Removing the effects of sources in the field using Miriad" />
<page pageid="1393" ns="0" title="Re-install an existing Miriad version">
<rev xml:space="preserve">If you have problems with your current binary version, e.g. missing shared libraries, you might have to re-install this version (or just install from source).
In order to do Miriad maintenance, you will need to use the mirboss alias, which adds the system commands in Miriad to your path:
== Re-link programs ==
The simplest approach is to assume a re-link is all you need. Try this:
% mir.prog itemize
and see if that still gives a shared library problem.
== Wrong compiler ==
It could be that you don't have the compiler (or even path) that was used in the binary. Edit the file in $MIR/localsys/compile.HOSTTYPE and try to recompile a program:
% edit $MIR/localsys/compile.darwin
% mir.prog itemize
== Mishap with pgplot ==
In one case, a gfortran based install did not want to recompile the libpgplot.so library in $MIRLIB because that compiler was a bit older and did not know how to compile the GIF driver. Edit the '''$MIRLIB/drivers.list''' file and comment out the two '''GIDRIV''' occurences. Then recompile as follows:
% mir.install pgplot subs prog
and check your recent log files in $MIR/tmp</rev>
<page pageid="1603" ns="0" title="Removing the continuum from narrow spectral line bands in Miriad">
<rev xml:space="preserve">(original text by Demerese Salter --- 11/15/2011)
(edited by Shaye Storm --- 11/16/2011)
* The task '''uvlin''' will try to remove the continuum but may not respect mosaicing and should therefore be used with caution. The task '''uvcal''' with '''options=contsub''' ought to do the same. There some good discussion up on [http://adsabs.harvard.edu/abs/1994A%26AS..107...55S]
* To subtract the continuum, it is best to work within the band where the line is. Flux offsets may exist between spectral windows depending on the separation between bands, and fitting the data with a linear polynomial to account for the spectral slope may not be sufficient. In addition, by subtracting the continuum from the data, you inherently introduce noise to the image, and increasing the bandwidth of the continuum determination only reduces this added noise according to the inverse square root of the number of channels. Therefore, the impact on the noise improvement decreases more quickly than the increasing bandwidth until the it doesn't make sense anymore to include more continuum channels in the solution. This effect is represented by the following equation:
sigma_line = sqrt ( (sigma^2)/n + (sigma^2)/m )
, where n is the number of channels in the line and m are the number of channels used in the continuum solution.
* One recommended method for continuum subtraction is to flag with '''uvflag''' the channels that should not be in the spectral line map. Take these channels and create a cleaned continuum map. Then use '''uvmodel''' to subtract the clean components that represent the continuum emission. Re-create the u,v data set without these components and proceed with inverting, cleaning, and restoring the new, line-only u,v data. For mosaiced data the added complexity here is that you will need to use '''demos''' to do this to individual fields and re-assemble later.
* An alternative method is to do the subtraction using the dirty maps. This is possible because of the linear nature of Fourier transforms: FT(A) - FT(B) = FT(A-B). The task '''maths''' should allow you to subtract one plane (e.g. the continuum) from n planes (e.g. the spectral line emission channels) if you use ''options=grow''. As an example:
maths exp='<'$LCUBE'>-working1' options=grow out=working2</rev>