<div dir="ltr">Hello, <div><br><div>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). </div><div>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.</div>
<div>Below are the headers of original file (before CONVL) and convolved file (after CONVL).</div><div>Can you please help me understand what is going on here?</div><div><br></div><div style><b>Original map header (before using CONVL)</b></div>
<div style><b><br></b></div><div><div>AIPS 2: Got(1) disk= 1 user=1306 type=MA M87_AX.ICL001.1</div><div>>imh</div><div>AIPS 2: Image=M87 (MA) Filename=M87_AX .ICL001. 1</div><div>AIPS 2: Telescope=VLA Receiver=VLA</div>
<div>AIPS 2: Observer=AH822 User #= 1306</div><div>AIPS 2: Observ. date=02-JUN-2003 Map date=20-SEP-2013</div><div>AIPS 2: Minimum=-2.67477240E-03 Maximum= 4.22793436E+00 JY/BEAM</div><div>AIPS 2: ----------------------------------------------------------------</div>
<div>AIPS 2: Type Pixels Coord value at Pixel Coord incr Rotat</div><div>AIPS 2: RA---SIN 2048 12 30 49.000 776.19 -0.025000 0.00</div><div>AIPS 2: DEC--SIN 1024 12 23 30.000 434.84 0.025000 0.00</div>
<div>AIPS 2: FREQ 1 8.4601120E+09 1.00 1.0000000E+08 0.00</div><div>AIPS 2: STOKES 1 1.0000000E+00 1.00 1.0000000E+00 0.00</div><div>AIPS 2: ----------------------------------------------------------------</div>
<div>AIPS 2: Coordinate equinox 2000.00</div><div>AIPS 2: Map type=NORMAL Number of iterations= 28669</div><div>AIPS 2: Conv size= 0.22688 X 0.22085 Position angle= -1.17</div><div>AIPS 2: Rest freq 0.000 Vel type: OPTICAL wrt YOU</div>
<div>AIPS 2: Alt ref. value 0.00000E+00 wrt pixel 1.00</div><div>AIPS 2: Maximum version number of extension files of type CC is 1</div><div>AIPS 2: Maximum version number of extension files of type CG is 1</div>
<div>AIPS 2: Maximum version number of extension files of type HI is 1</div><div>AIPS 2: Maximum version number of extension files of type ST is 1</div><div>AIPS 2: Maximum version number of extension files of type MF is 1</div>
<div>AIPS 2: Maximum version number of extension files of type PL is 1</div><div>AIPS 2: Keyword = 'CCFLUX ' value = 1.197020E+01</div><div>AIPS 2: Keyword = 'CCTOTAL ' value = 1.197020E+01</div><div>
AIPS 2: Keyword = 'CORRMODE' value = ' '</div><div>AIPS 2: Keyword = 'VLAIFS ' value = 'ABCD '</div><div>AIPS 2: Keyword = 'CORRCOEF' value = -1</div><div><br>
</div><div style><b>Convolved map header (after using CONVL)</b></div><div style><b><br></b></div><div style><div>AIPS 1: Got(1) disk= 1 user=1306 type=MA TEST-M87AX.CONVL.1</div><div>>imh</div><div>AIPS 1: Image=M87 (MA) Filename=TEST-M87AX .CONVL . 1</div>
<div>AIPS 1: Telescope=VLA Receiver=VLA</div><div>AIPS 1: Observer=AH822 User #= 1306</div><div>AIPS 1: Observ. date=02-JUN-2003 Map date=03-OCT-2013</div><div>AIPS 1: Minimum=-6.78434409E-03 Maximum= 4.42203140E+00 JY/BEAM</div>
<div>AIPS 1: ----------------------------------------------------------------</div><div>AIPS 1: Type Pixels Coord value at Pixel Coord incr Rotat</div><div>AIPS 1: RA---SIN 2048 12 30 49.000 776.19 -0.025000 0.00</div>
<div>AIPS 1: DEC--SIN 1024 12 23 30.000 434.84 0.025000 0.00</div><div>AIPS 1: FREQ 1 8.4601120E+09 1.00 1.0000000E+08 0.00</div><div>AIPS 1: STOKES 1 1.0000000E+00 1.00 1.0000000E+00 0.00</div>
<div>AIPS 1: ----------------------------------------------------------------</div><div>AIPS 1: Coordinate equinox 2000.00</div><div>AIPS 1: Map type=NORMAL Number of iterations= 28669</div><div>AIPS 1: Conv size= 0.41771 X 0.39941 Position angle= 49.54</div>
<div>AIPS 1: Rest freq 0.000 Vel type: OPTICAL wrt YOU</div><div>AIPS 1: Alt ref. value 0.00000E+00 wrt pixel 1.00</div><div>AIPS 1: Maximum version number of extension files of type HI is 1</div><div>
AIPS 1: Maximum version number of extension files of type CC is 1</div><div>AIPS 1: Maximum version number of extension files of type ST is 1</div><div>AIPS 1: Maximum version number of extension files of type MF is 1</div>
<div>AIPS 1: Keyword = 'CCFLUX ' value = 1.197020E+01</div><div>AIPS 1: Keyword = 'CCTOTAL ' value = 1.197020E+01</div><div>AIPS 1: Keyword = 'CORRMODE' value = ' '</div><div>AIPS 1: Keyword = 'VLAIFS ' value = 'ABCD '</div>
<div>AIPS 1: Keyword = 'CORRCOEF' value = -1</div><div>></div><div><br></div><div style>Thank you very much, </div></div><div><br></div>-- <br>Sayali S Avachat<br>PhD Candidate<br>Department of Physics and Space Sciences<br>
Florida Institute of Technology<br><a href="mailto:savachat2008@my.fit.edu" target="_blank">savachat2008@my.fit.edu</a>
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