[daip] IMAGR multiple fields: what's the issue with beam scaling? Also: CALIB with multiply concatenated VLBA datasets.
Eric Greisen
egreisen at nrao.edu
Sun Nov 25 18:07:43 EST 2007
SUSAN BILL WIDER writes:
> Eric, Amy.
>
> I'm running IMAGR with a couple of fields. The first field
looks about right with a maximum of 1.0 Jy for the beam but the second
field beam has a maximum of 4.0 Jy. How can this be? Aren't the
beams meant to have unity maximum? Or is there some additional
weighting that has to happen? The sum of the gridding weights in both
cases is the same so what's going on here? (PRTMSG capture appended.)
When there are large numbers of data samples, it is possible for the
accumulated round-off errors to cause bad beam values, esp in the
corneres of the image where the correction for the FFT of the
convolving function is vary large. If you look at these beams you
will see large positive and negative (1st field has -1.5 Jy as min)
values in the corners. IMAGR should be able to survive this.
>
> Another issue: I have concatenated multiple VLBA datasets
together to improve my sensitivity. The configuration of the arrays
in most of the datasets is the same but not always. Consequently, the
antenna numbering scheme for each sub-array changes --- say, if one
antenna was unanvailable. If I run CALIB on this multi-epoch
database, CALIB reports that some antennas get flagged because they
can't be tied across sub-arrays. This shouldn't happen, I think,
because all we need is that the sub-set of antennas in each effective
sub-array at each epoch should be linked. I don't remember this sort
of behavior with VLA multi-epoch data so is there something different
happening when a non-VLA array is involved?
It depends on how you have concatenated these data. If DBCON has
called them separate sub-arrays, then there should be no connection
between the subarrays in any case. The flagging to which you refer is
due to antennas being disconnected within a subarray - i.e. with no
way to relate the phase of the antenna to the phase of the reference
antenna.
Eric Greisen
>
> Bill
> blackhol AIPS (31DEC07) 131 23-NOV-2007 05:55:12 Page 1
> Pops Prior Date Time Task Messages for user 131
>
> 1 5 22-NOV-2007 21:54:18 IMAGR Task IMAGR (release of 31DEC07) begins
> 1 3 22-NOV-2007 21:55:04 IMAGR UVGET: Using flag table version 17 to edit data
> 1 2 22-NOV-2007 21:59:28 IMAGR Create 3C274 MC .IMAGR . 1 (UV) on disk 2 cno 1
> 1 4 22-NOV-2007 21:59:28 IMAGR Beginning channel 1 through 64 with 2 IFs
> 1 3 22-NOV-2007 22:12:58 IMAGR IMACPY: Copied 5327801 visibilities to be imaged
> 1 2 22-NOV-2007 22:13:01 IMAGR Create 3C274 MC U .IBM001. 2 (MA) on disk 1 cno 126
> 1 2 22-NOV-2007 22:13:01 IMAGR Create 3C274 MC U .IBM002. 2 (MA) on disk 1 cno 127
> 1 2 22-NOV-2007 22:13:01 IMAGR Create 3C274 MC U .ICL001. 2 (MA) on disk 1 cno 128
> 1 2 22-NOV-2007 22:13:01 IMAGR Create 3C274 MC U .ICL002. 2 (MA) on disk 1 cno 129
> 1 2 22-NOV-2007 22:13:03 IMAGR QINIT: did a GET of 5120 Kwords, OFF -344181861
> 1 2 22-NOV-2007 22:13:03 IMAGR GRDFLT: X and Y convolution type = SPHEROIDAL
> 1 2 22-NOV-2007 22:13:03 IMAGR GRDFLT: X and Y parms = 3.0000 1.0000
> 1 2 22-NOV-2007 22:13:03 IMAGR GRDFLT: convolution function sampled every 1/100 of a cell
> 1 2 22-NOV-2007 22:13:03 IMAGR GRDMEM: Ave 128 Channels; 3.245212E+08 to 3.403962E+08 Hz
> 1 4 22-NOV-2007 22:43:30 IMAGR Field 1 Sum of gridding weights = 1.34944E+02
> 1 4 22-NOV-2007 22:43:31 IMAGR Field 1 Beam min = -1.5 Jy, max = 1.0 Jy
> 1 4 22-NOV-2007 22:43:31 IMAGR Field 1 fit FWHM= 70.414 x 41.497 Milliarcsec, PA= -25.9
> 1 4 22-NOV-2007 23:03:02 IMAGR Field 2 Sum of gridding weights = 1.35039E+02
> 1 4 22-NOV-2007 23:03:04 IMAGR Field 2 Beam min = -1.4 Jy, max = 4.0 Jy
> 1 4 22-NOV-2007 23:03:04 IMAGR Field 2 fit FWHM= 70.435 x 41.507 Milliarcsec, PA= -25.9
> 1 4 22-NOV-2007 23:03:05 IMAGR CLBHIS: minimum component 0.500 of current peak
> 1 4 23-NOV-2007 00:17:16 IMAGR Field 1 min = -236.7 MilliJy,max = 1.2 Jy
> 1 4 23-NOV-2007 01:33:28 IMAGR Field 2 min = -127.4 MilliJy,max = 37.6 MilliJy
> 1 2 23-NOV-2007 01:33:29 IMAGR BGC Clean: using 1019 cell beam + residuals > 343.39 MilliJy
> 1 2 23-NOV-2007 01:33:31 IMAGR 226 Residual map points loaded
> 1 4 23-NOV-2007 01:33:31 IMAGR Field 1 min algorithm flux= 884.381 MilliJy iter= 4
> 1 3 23-NOV-2007 01:33:31 IMAGR Field 1 Clean flux density= 414.179 MilliJy 4 comps
> 1 3 23-NOV-2007 01:33:31 IMAGR Total Cleaned flux density = 414.179 MilliJy 4 comps
> 1 4 23-NOV-2007 01:33:31 IMAGR SETDO3: imaging done with multiple tangent planes
> 1 2 23-NOV-2007 01:33:31 IMAGR VISDFT: Begin DFT component subtraction
> 1 2 23-NOV-2007 01:33:31 IMAGR VISDFT: Model components of type Point
> 1 3 23-NOV-2007 01:33:31 IMAGR I Polarization model processed
> 1 2 23-NOV-2007 02:18:36 IMAGR BGC Clean: using 1019 cell beam + residuals > 343.39 MilliJy
> 1 2 23-NOV-2007 02:18:37 IMAGR 0 Residual map points loaded
> 1 4 23-NOV-2007 03:33:07 IMAGR Field 1 min = -192.5 MilliJy,max = 797.2 MilliJy
> 1 4 23-NOV-2007 04:49:13 IMAGR Field 2 min = -79.8 MilliJy,max = 28.9 MilliJy
> 1 2 23-NOV-2007 04:49:16 IMAGR BGC Clean: using 1019 cell beam + residuals > 228.67 MilliJy
> 1 2 23-NOV-2007 04:49:17 IMAGR 392 Residual map points loaded
> 1 4 23-NOV-2007 04:49:17 IMAGR Field 1 min algorithm flux= 459.853 MilliJy iter= 12
> 1 3 23-NOV-2007 04:49:17 IMAGR Field 1 Clean flux density= 894.323 MilliJy 12 comps
> 1 3 23-NOV-2007 04:49:17 IMAGR Total Cleaned flux density = 894.323 MilliJy 12 comps
> 1 2 23-NOV-2007 04:49:17 IMAGR VISDFT: Begin DFT component subtraction
> 1 3 23-NOV-2007 04:49:17 IMAGR I Polarization model processed
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