[daip] issues with task CONVL

[Sayali Avachat]

Hello,

I am trying to convolve radio maps at different frequencies to the
resolution of a map at one particular frequency (15GHz resolution at B
config).
What I observed is, the task CONVL can convolve the beam parameters, viz
bmaj, bmin and bpa, fine, but I don't know why it affects the flux minimum
and maximum values in the header of original file. I don't think CONVL is
suppose to change anything but beam parameters of the specified image.
Below are the headers of original file (before CONVL) and convolved file
(after CONVL).
Can you please help me understand what is going on here?

*Original map header (before using CONVL)*
*
*
AIPS 2: Got(1)   disk= 1  user=1306   type=MA   M87_AX.ICL001.1
>imh
AIPS 2: Image=M87       (MA)         Filename=M87_AX      .ICL001.   1
AIPS 2: Telescope=VLA                Receiver=VLA
AIPS 2: Observer=AH822               User #= 1306
AIPS 2: Observ. date=02-JUN-2003     Map date=20-SEP-2013
AIPS 2: Minimum=-2.67477240E-03      Maximum= 4.22793436E+00 JY/BEAM
AIPS 2: ----------------------------------------------------------------
AIPS 2: Type    Pixels   Coord value     at Pixel     Coord incr   Rotat
AIPS 2: RA---SIN  2048    12 30 49.000     776.19      -0.025000    0.00
AIPS 2: DEC--SIN  1024    12 23 30.000     434.84       0.025000    0.00
AIPS 2: FREQ         1   8.4601120E+09       1.00  1.0000000E+08    0.00
AIPS 2: STOKES       1   1.0000000E+00       1.00  1.0000000E+00    0.00
AIPS 2: ----------------------------------------------------------------
AIPS 2: Coordinate equinox 2000.00
AIPS 2: Map type=NORMAL              Number of iterations=   28669
AIPS 2: Conv size= 0.22688 X 0.22085   Position angle=  -1.17
AIPS 2: Rest freq      0.000         Vel type: OPTICAL wrt YOU
AIPS 2: Alt ref. value  0.00000E+00  wrt pixel    1.00
AIPS 2: Maximum version number of extension files of type CC is   1
AIPS 2: Maximum version number of extension files of type CG is   1
AIPS 2: Maximum version number of extension files of type HI is   1
AIPS 2: Maximum version number of extension files of type ST is   1
AIPS 2: Maximum version number of extension files of type MF is   1
AIPS 2: Maximum version number of extension files of type PL is   1
AIPS 2: Keyword = 'CCFLUX  '  value =  1.197020E+01
AIPS 2: Keyword = 'CCTOTAL '  value =  1.197020E+01
AIPS 2: Keyword = 'CORRMODE'  value = '        '
AIPS 2: Keyword = 'VLAIFS  '  value = 'ABCD    '
AIPS 2: Keyword = 'CORRCOEF'  value =           -1

*Convolved map header (after using CONVL)*
*
*
AIPS 1: Got(1)   disk= 1  user=1306   type=MA   TEST-M87AX.CONVL.1
>imh
AIPS 1: Image=M87       (MA)         Filename=TEST-M87AX  .CONVL .   1
AIPS 1: Telescope=VLA                Receiver=VLA
AIPS 1: Observer=AH822               User #= 1306
AIPS 1: Observ. date=02-JUN-2003     Map date=03-OCT-2013
AIPS 1: Minimum=-6.78434409E-03      Maximum= 4.42203140E+00 JY/BEAM
AIPS 1: ----------------------------------------------------------------
AIPS 1: Type    Pixels   Coord value     at Pixel     Coord incr   Rotat
AIPS 1: RA---SIN  2048    12 30 49.000     776.19      -0.025000    0.00
AIPS 1: DEC--SIN  1024    12 23 30.000     434.84       0.025000    0.00
AIPS 1: FREQ         1   8.4601120E+09       1.00  1.0000000E+08    0.00
AIPS 1: STOKES       1   1.0000000E+00       1.00  1.0000000E+00    0.00
AIPS 1: ----------------------------------------------------------------
AIPS 1: Coordinate equinox 2000.00
AIPS 1: Map type=NORMAL              Number of iterations=   28669
AIPS 1: Conv size= 0.41771 X 0.39941   Position angle=  49.54
AIPS 1: Rest freq      0.000         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 HI is   1
AIPS 1: Maximum version number of extension files of type CC is   1
AIPS 1: Maximum version number of extension files of type ST is   1
AIPS 1: Maximum version number of extension files of type MF is   1
AIPS 1: Keyword = 'CCFLUX  '  value =  1.197020E+01
AIPS 1: Keyword = 'CCTOTAL '  value =  1.197020E+01
AIPS 1: Keyword = 'CORRMODE'  value = '        '
AIPS 1: Keyword = 'VLAIFS  '  value = 'ABCD    '
AIPS 1: Keyword = 'CORRCOEF'  value =           -1
>

Thank you very much,

-- 
Sayali S Avachat
PhD Candidate
Department of Physics and Space Sciences
Florida Institute of Technology
savachat2008 at my.fit.edu
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