UVMODEL amplitude question
Posted: Tue Jul 22, 2014 8:37 am
Hi
I've been trying to create a fake gaussian source with the same u-v coverage as my other data, using:
----------------------------------------------------------------
invert vis=mydata map=mymap beam=mybeam stokes=i line=channel,75,550,1,1 robust=-1.0 cell=0.2,0.2 imsize=5000,9000 options=mfs
imgen in=mymap out=fakegauss object=gaussian factor=0 spar=1.0,0,0,180,180,0
uvmodel vis=mydata model=fakegauss out=fakedata options=replace,mfs
invert vis=fakedata map=fakemap beam=fakebeam stokes=i robust=-1.0 cell=0.2,0.2 imsize=3000,3000 options=mfs
----------------------------------------------------------------
When I use mfs in invert, I get an amplitude I can't understad in the final "fakemap" image.
When I do an imstat on the central 1000 pixels of the fakemap image, I get:
Axis 3 (FREQ-LSR)
plane Frequency Sum Mean rms Maximum Minimum Npoints
1 2.0 5.096E+09 5.085E+03 2.349E+03 9.691E+03 -55.0 1002001
So to check, I re-did the second invert above for a range of channels individually, using
line=channel,75,550,1,1 slop=1,zero
I then did an imstat on the central 1000 pixels of the image, and I get:
plane Frequency Sum Mean rms Maximum Minimum Npoints
1 2.0 1.365E+10 1.363E+04 6.405E+03 2.619E+04 -384. 1002001
2 2.0 1.513E+10 1.510E+04 5.529E+03 2.592E+04 3.291E+03 1002001
3 2.0 1.379E+10 1.376E+04 6.431E+03 2.638E+04 -272. 1002001
4 2.0 1.346E+10 1.343E+04 6.381E+03 2.597E+04 -523. 1002001
5 2.0 1.395E+10 1.392E+04 6.524E+03 2.673E+04 -291. 1002001
6 2.0 1.389E+10 1.386E+04 6.490E+03 2.660E+04 -338. 1002001
7 2.0 1.206E+10 1.203E+04 6.325E+03 2.452E+04-1.087E+03 1002001
8 2.0 1.374E+10 1.371E+04 6.404E+03 2.633E+04 14.6 1002001
9 2.0 1.393E+10 1.390E+04 6.525E+03 2.671E+04 -358. 1002001
10 2.0 1.391E+10 1.389E+04 6.519E+03 2.669E+04 -309. 1002001
11 2.0 1.398E+10 1.395E+04 6.473E+03 2.666E+04 -95.5 1002001
12 2.0 1.392E+10 1.390E+04 6.548E+03 2.676E+04 -341. 1002001
13 2.0 1.395E+10 1.393E+04 6.551E+03 2.680E+04 -336. 1002001
14 2.0 1.397E+10 1.394E+04 6.557E+03 2.682E+04 -405. 1002001
...
So the mfs map has a maximum of 9.691E+03, where in the per-channel map I have a maximum of ~2.6E+04 in each channel.
* How does this relate to the amplitude of 1 that I gave my original Gaussian image?
* Why is the mfs amplitude lower than the per-channel maxima?
Thanks!
I've been trying to create a fake gaussian source with the same u-v coverage as my other data, using:
----------------------------------------------------------------
invert vis=mydata map=mymap beam=mybeam stokes=i line=channel,75,550,1,1 robust=-1.0 cell=0.2,0.2 imsize=5000,9000 options=mfs
imgen in=mymap out=fakegauss object=gaussian factor=0 spar=1.0,0,0,180,180,0
uvmodel vis=mydata model=fakegauss out=fakedata options=replace,mfs
invert vis=fakedata map=fakemap beam=fakebeam stokes=i robust=-1.0 cell=0.2,0.2 imsize=3000,3000 options=mfs
----------------------------------------------------------------
When I use mfs in invert, I get an amplitude I can't understad in the final "fakemap" image.
When I do an imstat on the central 1000 pixels of the fakemap image, I get:
Axis 3 (FREQ-LSR)
plane Frequency Sum Mean rms Maximum Minimum Npoints
1 2.0 5.096E+09 5.085E+03 2.349E+03 9.691E+03 -55.0 1002001
So to check, I re-did the second invert above for a range of channels individually, using
line=channel,75,550,1,1 slop=1,zero
I then did an imstat on the central 1000 pixels of the image, and I get:
plane Frequency Sum Mean rms Maximum Minimum Npoints
1 2.0 1.365E+10 1.363E+04 6.405E+03 2.619E+04 -384. 1002001
2 2.0 1.513E+10 1.510E+04 5.529E+03 2.592E+04 3.291E+03 1002001
3 2.0 1.379E+10 1.376E+04 6.431E+03 2.638E+04 -272. 1002001
4 2.0 1.346E+10 1.343E+04 6.381E+03 2.597E+04 -523. 1002001
5 2.0 1.395E+10 1.392E+04 6.524E+03 2.673E+04 -291. 1002001
6 2.0 1.389E+10 1.386E+04 6.490E+03 2.660E+04 -338. 1002001
7 2.0 1.206E+10 1.203E+04 6.325E+03 2.452E+04-1.087E+03 1002001
8 2.0 1.374E+10 1.371E+04 6.404E+03 2.633E+04 14.6 1002001
9 2.0 1.393E+10 1.390E+04 6.525E+03 2.671E+04 -358. 1002001
10 2.0 1.391E+10 1.389E+04 6.519E+03 2.669E+04 -309. 1002001
11 2.0 1.398E+10 1.395E+04 6.473E+03 2.666E+04 -95.5 1002001
12 2.0 1.392E+10 1.390E+04 6.548E+03 2.676E+04 -341. 1002001
13 2.0 1.395E+10 1.393E+04 6.551E+03 2.680E+04 -336. 1002001
14 2.0 1.397E+10 1.394E+04 6.557E+03 2.682E+04 -405. 1002001
...
So the mfs map has a maximum of 9.691E+03, where in the per-channel map I have a maximum of ~2.6E+04 in each channel.
* How does this relate to the amplitude of 1 that I gave my original Gaussian image?
* Why is the mfs amplitude lower than the per-channel maxima?
Thanks!