[daip] RUNNING RM synthesis tasks (or getting ready to do so)

[Eric Greisen]

On 06/08/2016 01:25 PM, Eric Perlman wrote:
> Hi,
>
> I am trying to do a rotation measure synthesis analysis on some recent
> VLBA data.  I would like to do it using DOFARS but am having trouble
> getting my data ready to do so.  I am using AIPS version 31-DEC-2015.
>
> To this point, I have done the following:
>
> 1) Run SPLIT (with APARM=0) on the data, which has been polarization
> calibrated.
>
> 2) Obtained a high-quality self-calibrated Stokes I image, using
> multiple iterations of self-cal.
>
> 3) Self-calibrated the data with that Stokes I image.
>
> 4) Run IMAGR with no cleaning, FREQID=-1 and FQTOL=-1 to create Stokes
> Q, U, V images.
>      This created an image that has a header that looks like this:
> AIPS 1: Image=NGC4845   (MA)         Filename=NGC4845     .QIM001. 1
> AIPS 1: Telescope=VLBA               Receiver=VLBA
> AIPS 1: Observer=BP191               User #= 1806
> AIPS 1: Observ. date=08-OCT-2015     Map date=06-JUN-2016
> AIPS 1: Minimum=-3.21130268E-03      Maximum= 2.84131849E-03 JY/BEAM
> AIPS 1: ----------------------------------------------------------------
> AIPS 1: Type    Pixels   Coord value     at Pixel     Coord incr Rotat
> AIPS 1: RA---SIN  1024    12 58 01.197     512.00      -0.000300 0.00
> AIPS 1: DEC--SIN  1024    01 34 32.420     513.00       0.000300 0.00
> AIPS 1: FREQ       128   4.8520000E+09       1.00  2.5000000E+05 0.00
> AIPS 1: STOKES       1   2.0000000E+00       1.00  1.0000000E+00 0.00
> AIPS 1: ----------------------------------------------------------------
> AIPS 1: Coordinate equinox 2000.00
> AIPS 1: Map type=DIRTY               Number of iterations=       0
> AIPS 1: Conv size= 0.00296 X 0.00126   Position angle=   0.61
> AIPS 1: Rest freq   4852.000         Vel type: OPTICAL wrt YOU
> AIPS 1: Alt ref. value  0.00000E+00  wrt pixel    1.00
> AIPS 1: Maximum version number of extension files of type CG is   1
> AIPS 1: Maximum version number of extension files of type HI is   1
> AIPS 1: Keyword = 'WTNOISE '  value =  1.19735482D+00
> AIPS 1: Keyword = 'SUMWTIN '  value =  4.81890338D+00
> AIPS 1: Keyword = 'OLDRFQ  '  value =  4.85200000D+09
> AIPS 1: Keyword = 'CORRELAT'  value = 'DIFX    '
> AIPS 1: Keyword = 'MAXABSU '  value = -1.000000E+00
>
> When I try to run FQUBE the following error messages appear:
>

Why are you running FQUBE or MCUBE??  You already have cubes in Q and U 
and I (V is of little use).  These are the inputs to DOFARS (the Q and U 
images are INNAME and IN2NAME) which will transpose them and then run 
FARS.  Note that you will need the transposed Q and U cubes for both 
FARS and RMFIT so it is probably better to use TRANS and then FARS 
directly rather than have to do the transposition over again for RMFIT.

Be sure to study teh relevant portions of AIPS Memo 118 to learn about 
RMFIT.  You do not have a particularly long freq axis so the FARS output 
will be disappointing.  RMFIT may be able to pull some info out however...

Eric Greisen