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GLOW Interferometry Tutorial: Wednesday
We will reduce the 3C129 polarization continuum dataset from the 2008 NRAO summer school. (See http://casa.nrao.edu/Tutorial/SIworkshop2008/ ) The summer school used CASA for the data reduction. You are welcome to try to use CASA for the data reduction on your own (but see also the warnings about what to do what CASA crashes frequently), but we will do the basic reduction in AIPS.
2010 Nov 16: JMA updated for 31DEC10 AIPS
Web Image of 3C129
Wide-field 90 cm image of the large head-tail radio galaxy 3C129 (right). The bright source at the left is 3C129.1. From Lane et al., AJ, 123, 2985, 2002.
The 5 GHz observations being reduced here will only look at the central, brightest, portion of this source.
Data Reduction
Remember, the purpose f this exercise is not to teach you how to reduce radio interferometry data with AIPS. Consider all of the arcane incantations below as just that, magic incantations. You should instead try to figure out what each step is actually doing to the data. The AIPS Cookbook has quite a bit of information to help guide you. Check out chapters 4 and 5. (Note that you probably have a copy of the cookbook in your local AIPS installation if you don't have full web access.) However, at some of the most important points, the cookbook is relatively useless for understanding what is going on, as opposed to knowing which buttons to push, so ask your tutorial leader for help in this area.
Download the data from http://casa.nrao.edu/Data/VLA/3C129/3c129data.tgz and untar it in some directory. (If you are in Garching, there should be a local copy. Ask Sven.) Then, from that same directory, start aips. Login with a new user ID number.
Basic Environment
dowait 1
dohist=1
docrt=132
dotv=1
Load the raw data: FILLM
task 'fillm'
default
nfiles 0
prtlev 0
datain 'PWD:AT166_
doconcat true
clron
doweight 10
ncount 2
cparm(4)=28
cparm(8)=10./60
go
Check where it went. You will need the C band version at 5 GHz
pcat
getn 4
imhe
Print out some useful information
task 'listr'
default
getn 4
optype 'scan'
doweight 1
go
AIPS 1: Got(1) disk= 1 user= 101 type=UV 19940725.C BAND.2
vlb054 LISTR(31DEC08) 101 13-NOV-2008 15:25:41 Page 1
File = 19940725 .C BAND. 2 Vol = 1 Userid = 101
Freq = 4.885100000 GHz Ncor = 4 No. vis = 216975
Scan summary listing
Scan Source Qual Calcode Sub Timerange FrqID START VIS END VIS
1 2345-167 : 0003 A 1 0/07:41:45 - 0/07:43:25 1 1 2917
2 A2597 : 0003 1 0/08:00:25 - 0/08:02:35 1 2918 6788
3 2345-167 : 0003 A 1 0/08:21:05 - 0/08:22:45 1 6789 9709
4 A2597 : 0003 1 0/08:39:45 - 0/08:41:55 1 9710 13605
5 2345-167 : 0003 A 1 0/09:00:25 - 0/09:02:05 1 13606 16505
6 A2597 : 0003 1 0/09:19:05 - 0/09:21:15 1 16506 20401
7 2345-167 : 0003 A 1 0/09:39:45 - 0/09:41:25 1 20402 23322
8 A2597 : 0003 1 0/09:58:25 - 0/10:00:35 1 23323 27218
9 2345-167 : 0003 A 1 0/10:19:05 - 0/10:20:45 1 27219 30140
10 A2597 : 0003 1 0/10:37:45 - 0/10:39:55 1 30141 34036
11 2345-167 : 0003 A 1 0/10:58:25 - 0/11:00:05 1 34037 36957
12 A2597 : 0003 1 0/11:17:05 - 0/11:19:15 1 36958 40832
13 2345-167 : 0003 A 1 0/11:37:45 - 0/11:39:25 1 40833 43702
14 0420+417 : 0003 B 1 0/11:48:25 - 0/11:50:05 1 43703 46624
15 3C129 : 0003 1 0/12:12:55 - 0/12:23:05 1 46625 66120
16 0420+417 : 0003 B 1 0/12:27:25 - 0/12:29:05 1 66121 69041
17 3C129 : 0003 1 0/12:50:05 - 0/12:56:05 1 69042 80412
18 3C129 : 0003 1 0/12:56:25 - 0/13:00:15 1 80413 88498
19 0420+417 : 0003 B 1 0/13:04:35 - 0/13:06:15 1 88499 91419
20 3C129 : 0003 1 0/13:29:05 - 0/13:39:15 1 91420 109415
21 0420+417 : 0003 B 1 0/13:43:35 - 0/13:45:15 1 109416 112112
22 3C129 : 0003 1 0/14:06:15 - 0/14:16:25 1 112113 130108
23 0420+417 : 0003 B 1 0/14:20:45 - 0/14:22:25 1 130109 132636
24 3C129 : 0003 1 0/14:45:15 - 0/14:55:25 1 132637 150081
25 0420+417 : 0003 B 1 0/14:59:45 - 0/15:01:25 1 150082 152778
26 3C129 : 0003 1 0/15:18:25 - 0/15:25:35 1 152779 164366
27 0420+417 : 0003 B 1 0/15:30:05 - 0/15:31:45 1 164367 166846
28 3C129 : 0003 1 0/15:55:05 - 0/16:05:15 1 166847 183403
29 0420+417 : 0003 B 1 0/16:10:05 - 0/16:11:45 1 183404 185861
30 3C129 : 0003 1 0/16:34:55 - 0/16:45:05 1 185862 203522
31 0420+417 : 0003 B 1 0/16:49:35 - 0/16:51:15 1 203523 206216
32 0518+165 : 0003 C 1 0/17:06:35 - 0/17:09:45 1 206217 211608
33 0134+329 : 0003 C 1 0/17:21:45 - 0/17:24:55 1 211609 216975
Source summary
Velocity type = ' ' Definition = ' '
ID Source Qual Calcode RA(1950.0) Dec(1950.0) IFlux QFlux UFlux VFlux No. vis
1 2345-167 : 0003 A 23:45:27.6823 -16:47:52.600 0.000 0.000 0.000 0.000 20372
IF( 2) 0.000 0.000 0.000 0.000
2 A2597 : 0003 23:22:43.7000 -12:23:56.000 0.000 0.000 0.000 0.000 23330
IF( 2) 0.000 0.000 0.000 0.000
3 0420+417 : 0003 B 04:20:27.9370 41:43:08.045 0.000 0.000 0.000 0.000 24318
IF( 2) 0.000 0.000 0.000 0.000
4 3C129 : 0003 04:45:31.6950 44:55:19.950 0.000 0.000 0.000 0.000 138196
IF( 2) 0.000 0.000 0.000 0.000
5 0518+165 : 0003 C 05:18:16.5320 16:35:26.900 0.000 0.000 0.000 0.000 5392
IF( 2) 0.000 0.000 0.000 0.000
6 0134+329 : 0003 C 01:34:49.8320 32:54:20.520 0.000 0.000 0.000 0.000 5367
IF( 2) 0.000 0.000 0.000 0.000
ID Source Freq(GHz) Velocity(Km/s) Rest freq (GHz)
1 All Sources 4.8851 0.0000 0.0000
IF( 2) 4.5851 0.0000 0.0000
Frequency Table summary
FQID IF# Freq(GHz) BW(kHz) Ch.Sep(kHz) Sideband
1 1 4.88510000 50000.0039 50000.0039 1
2 4.58510000 50000.0039 50000.0039 1
AIPS 1: Resumes
Where are the antennas located?
go prtan
Location Of VLA Antennas
N36 (26)
N32 ( 1)
N28 (19)
N24 (11)
N20 (15)
N16 (25)
N12 (13)
N8 (27)
N4 (14)
(12) W4 E4 (22)
( 8) W8 E8 ( 4)
( 3) W12 E12 (16)
(28) W16 E16 ( 7)
( 2) W20 E20 (17)
(21) W24 E24 (24)
(10) W28 E28 ( 5)
(18) W32 E32 (23)
(20) W36 E36 ( 6)
VLA:_OUT ( 9)
VPT:_OUT (29)
Flag some bad data. Just run the commands.
task 'uvflg'
default
dohist 1
getn 4
antenna 1,0
basel 0
timer 0 13 45 20 0 15 0 0
stokes ' '
opcode 'flag'
reason 'bad ant'
outfgver 1
go
antenna 14,0
timer 0 16 50 50 0 16 51 0
go
timer 0
Investigate the data
Plots
task 'uvplt'
source '0518+165',' '
calcode ' '
stokes 'half'
timer 0
uvrange 0
bif 0
eif 0
docalib 0
gainuse 1
bparm 0 1
do3col 1
dotv 1
tvinit
go
source '0134+329',' '
tvinit
go
source '0420+417', ' '
tvinit
go
source '3C129', ' '
tvinit
go
bparm 6 7
source '0518+165',' '
tvinit
go
source '0134+329',' '
tvinit
go
source '0420+417', ' '
tvinit
go
source '3C129', ' '
tvinit
go
bparm 0
Raw visibilities
task 'listr'
optype 'list'
antenna 22,0
basel 0
sources ' '
calcode '*'
bif 0
eif 0
docalib 0
Start the calibration
Set the flux values of the known calibrators
task 'setjy'
default
getn 4
source '0518+165',' '
bif 0
eif 0
optype 'calc'
aparm(2) 2
go
vlb054> SETJY1: Task SETJY (release of 31DEC08) begins vlb054> SETJY1: **WARNING: OPCODE=CALC AND FREQID = -1 vlb054> SETJY1: FREQID WILL BE RESET TO 1, CHECK YOUR RESULTS CAREFULLY vlb054> SETJY1: A source model for this calibrator may be available vlb054> SETJY1: Use the verb CALDIR to see if there is one vlb054> SETJY1: A source model for this calibrator may be available vlb054> SETJY1: Use the verb CALDIR to see if there is one vlb054> SETJY1: / Flux calculated using known spectrum vlb054> SETJY1: BIF = 1 EIF = 2 /Range of IFs vlb054> SETJY1: '0518+165 ' IF = 1 FLUX = 3.7742 (Jy calcd) vlb054> SETJY1: '0518+165 ' IF = 2 FLUX = 3.9464 (Jy calcd) vlb054> SETJY1: / Using (1995.2) VLA or Reynolds (1934-638) coefficients vlb054> SETJY1: Appears to have ended successfully vlb054> SETJY1: vlb054 31DEC08 TST: Cpu= 0.0 Real= 0
bif 1
eif 1
optype ' '
zerosp 3.7742, 0.380, -0.153, 0.0
go
bif 2
eif 2
zerosp 3.9464, 0.397, -0.161, 0.0
go
bif 0
eif 0
zerosp 0
optype 'calc'
source = '0134+329',' '
go
vlb054> SETJY1: Task SETJY (release of 31DEC08) begins vlb054> SETJY1: **WARNING: OPCODE=CALC AND FREQID = -1 vlb054> SETJY1: FREQID WILL BE RESET TO 1, CHECK YOUR RESULTS CAREFULLY vlb054> SETJY1: A source model for this calibrator may be available vlb054> SETJY1: Use the verb CALDIR to see if there is one vlb054> SETJY1: A source model for this calibrator may be available vlb054> SETJY1: Use the verb CALDIR to see if there is one vlb054> SETJY1: / Flux calculated using known spectrum vlb054> SETJY1: BIF = 1 EIF = 2 /Range of IFs vlb054> SETJY1: '0134+329 ' IF = 1 FLUX = 5.4891 (Jy calcd) vlb054> SETJY1: '0134+329 ' IF = 2 FLUX = 5.8249 (Jy calcd) vlb054> SETJY1: / Using (1995.2) VLA or Reynolds (1934-638) coefficients vlb054> SETJY1: Appears to have ended successfully vlb054> SETJY1: vlb054 31DEC08 TST: Cpu= 0.0 Real= 0
Get images (and thus clean components) for the calibrators
task 'calrd'
object '3c138'
band 'c'
go
object '3c48'
band 'c'
go
pcat
AIPS 1: Catalog on disk 1 AIPS 1: Cat Usid Mapname Class Seq Pt Last access Stat AIPS 1: 1 101 19940725 .C BAND. 1 UV 13-NOV-2008 15:24:44 AIPS 1: 2 101 19940725 .X BAND. 1 UV 13-NOV-2008 15:23:05 AIPS 1: 3 101 19940725 .X BAND. 2 UV 13-NOV-2008 16:01:14 AIPS 1: 4 101 19940725 .C BAND. 2 UV 13-NOV-2008 16:06:34 AIPS 1: 5 101 19940725 .U BAND. 1 UV 13-NOV-2008 15:23:05 AIPS 1: 6 101 3C138_C .MODEL . 1 MA 13-NOV-2008 16:09:02 AIPS 1: 7 101 3C48_C .MODEL . 1 MA 13-NOV-2008 16:09:22
Convert them to the coordinate system used for the observations
task 'eposw'
getn 6
eposw
getn 7
eposw
Do the actual calibration. Start with 3C138
task 'calib'
default
getn 4
calsour '0518+165',' '
uvrange 0
antenna 0
refant 22
minamper 10
minphser 10
weightit 1
get2n 6
ncomp 0
solmode 'A&P'
aparm(6) 2
solint 2
solsub 2
cparm(3) 10
cparm(4) 10
go
clrmsg
Calibrate 3C48
calsour '0134+329',' '
get2n 7
go
clrmsg
Calibrate the phase calibrator
clr2n
calsour '0420+417', ' '
solint 0
uvrange 20 0
go
clrmsg
Check the results
task 'snplt'
antenna 0
stokes ' '
inext 'sn'
inver 1
sources ' '
timer 0
optype 'amp'
opcode 'alsi'
do3col 1
dotv 1
nplots 9
tvinit
go
optype 'phas'
go
inver 2
optype 'amp'
go
optype 'phas'
go
inver 3
optype 'amp'
go
optype 'phas'
go
Apply the calibration to the phase calibrator
task 'getjy'
sources '0420+417', ' '
calsour '0518+165','0134+329',' '
calcode ' '
bif 0
eif 0
antenna 0
timer 0
snver 0
go
vlb054> GETJY1: Task GETJY (release of 31DEC08) begins vlb054> GETJY1: Source:Qual CALCODE IF Flux (Jy) vlb054> GETJY1: 0420+417 : 3 B 1 1.46472 +/- 0.00304 vlb054> GETJY1: 2 1.46512 +/- 0.00341 vlb054> GETJY1: Appears to have ended successfully vlb054> GETJY1: vlb054 31DEC08 TST: Cpu= 0.0 Real= 0
Redo the phase calibrator calibration
Now that the flux density of the phase calibrator has been found, redo its calibration (just to make sure there are no remnants of some subtle assumptions about its flux density left in AIPS).
inext 'sn'
inver 3
extdest
inver 0
tget calib
go
clrmsg
Apply the calibration to all sources of interest.
task 'clcal'
sources '0518+165','0134+329','0420+417', '3C129', ' '
calsour '0518+165','0134+329','0420+417', ' '
opcode 'cali'
gainver 1
gainuse 2
refant 22
interp '2pt'
doblank 1
go
Have a look at the calibration
Plots
task 'uvplt'
docalib 1
gainuse 2
source '0420+417', ' '
stokes 'half'
aparm 0
bparm 0 1
doweight 1
uvrange 0
tvinit
go
Start the polarization calibration
Check the parallactic angle change
task 'listr'
sources '0518+165','0134+329','0420+417', ' '
inext 'cl'
inver 2
optype 'gain'
dparm 9,0
go
Make a backup of calibration values, in case we mess up
task 'tasav'
clro
go
Now do the polarization calibration using the phase calibrator
task 'pcal'
calsour '0420+417', ' '
timer 0
antenna 0
uvrange 20,0
bif 0
eif 0
docalib 1
gainuse 2
clr2n
pmodel 0
solint 3
soltype 'appr'
prtlev 1
refant 22
bparm 0
cparm 0
go
clrmsg
vlb054> PCAL 1: Calibration source 1 vlb054> PCAL 1: Q+iU=( -0.01035, 0.03766) +/- ( 0.000106, 0.000106) Jy vlb054> PCAL 1: Pol. inten. = 0.03905 +/- 0.000150 Jy, angle = 52.68 +/- vlb054> 0.078 deg vlb054> PCAL 1: 0420+417 I,Q,U,V = 1.4647 -0.01035 0.03766 0.00000 J vlb054> y vlb054> PCAL 1: Calibration source 1 vlb054> PCAL 1: Q+iU=( -0.03423, 0.00815) +/- ( 0.000114, 0.000114) Jy vlb054> PCAL 1: Pol. inten. = 0.03519 +/- 0.000161 Jy, angle = 83.31 +/- vlb054> 0.093 deg vlb054> PCAL 1: 0420+417 I,Q,U,V = 1.4651 -0.03423 0.00815 0.00000 J vlb054> y
Using the calibration, check the difference between polarizations on a polarized calibrator
task 'rldif'
source '0518+165', ' '
timer 0
antenna 0
uvrange 0,45
docalib 1
gainuse 2
dopol true
go
Ampscalar average of matrix = -30.19( 0.081) sigma = 1.160 Ampscalar average of matrix = 33.93( 0.097) sigma = 1.389
outputs
AIPS 1: RLDIF: Task to return Right - Left phase difference AIPS 1: Adverbs Values Comments AIPS 1: ---------------------------------------------------------------- AIPS 1: CLCORPRM -30.1863 33.9257 R-L phase difference returned AIPS 1: *rest 0
Another save, just in case
task 'tasav'
clro
go
What is the angle supposed to be for this calibrator?
Polarization data for C band from http://www.vla.nrao.edu/astro/calib/polar/1999/
Correct number is -21.71
Correct the measured values
for i=1 to 2;clcorp(i) = -21.71 - clcorp(i);end
Apply them
task 'clcor'
source ' '
antenna 0
timer 0
bif 0
eif 0
gainver 2
gainuse 0
opcode 'polr'
stokes 'l'
go
Check that the angles match what we expect
task 'rldif'
source '0518+165', ' '
timer 0
antenna 0
uvrange 0,45
docalib 1
gainuse 3
dopol true
go
Look at what AIPS gave back
outputs
AIPS 1: RLDIF: Task to return Right - Left phase difference AIPS 1: Adverbs Values Comments AIPS 1: ---------------------------------------------------------------- AIPS 1: CLCORPRM -21.71 -21.71 R-L phase difference returned AIPS 1: *rest 0
###############
Now start with the smaller array data. Load it in
FILLM
task 'fillm'
default
nfiles 2
prtlev 0
datain 'PWD:AT166_
doconcat true
clron
doweight 10
ncount 1
cparm(4)=28
cparm(8)=10./60
go
Check where it went
pcat
AIPS 1: Catalog on disk 1 AIPS 1: Cat Usid Mapname Class Seq Pt Last access Stat AIPS 1: 1 101 19940725 .C BAND. 1 UV 13-NOV-2008 17:24:12 AIPS 1: 2 101 19940725 .X BAND. 1 UV 13-NOV-2008 17:24:13 AIPS 1: 3 101 19940725 .X BAND. 2 UV 13-NOV-2008 17:24:13 AIPS 1: 4 101 19940725 .C BAND. 2 UV 13-NOV-2008 17:24:13 AIPS 1: 5 101 19940725 .U BAND. 1 UV 13-NOV-2008 17:24:13 AIPS 1: 6 101 3C138_C .MODEL . 1 MA 13-NOV-2008 16:16:53 AIPS 1: 7 101 3C48_C .MODEL . 1 MA 13-NOV-2008 16:19:09 AIPS 1: 8 101 19940725 .TASAV . 1 UV 13-NOV-2008 17:24:13 AIPS 1: 9 101 19940725 .TASAV . 2 UV 13-NOV-2008 17:24:13 AIPS 1: 10 101 19941103 .C BAND. 1 UV 13-NOV-2008 17:24:36 AIPS 1: 11 101 19941103 .X BAND. 1 UV 13-NOV-2008 17:24:36 AIPS 1: 12 101 19941103 .X BAND. 2 UV 13-NOV-2008 17:24:36 AIPS 1: 13 101 19941103 .C BAND. 2 UV 13-NOV-2008 17:24:36
Makre sure we have the right one
getn 13
imhe
Get the scan information
task 'listr'
default
getn 13
optype 'scan'
doweight 1
go
vlb054 LISTR(31DEC08) 101 13-NOV-2008 17:25:15 Page 1
File = 19941103 .C BAND. 2 Vol = 1 Userid = 101
Freq = 4.885100000 GHz Ncor = 4 No. vis = 52167
Scan summary listing
Scan Source Qual Calcode Sub Timerange FrqID START VIS END VIS
1 0134+329 : 0003 C 1 0/04:05:15 - 0/04:07:25 1 1 36
2 0420+417 : 0003 B 1 0/07:33:35 - 0/07:35:15 1 37 3169
3 0518+165 : 0003 C 1 0/07:42:35 - 0/07:45:45 1 3170 9457
4 3C129 : 0003 1 0/08:18:05 - 0/08:23:25 1 9458 20308
5 0420+417 : 0003 B 1 0/08:27:35 - 0/08:29:15 1 20309 22845
6 0420+417 : 0003 B 1 0/08:49:25 - 0/08:51:05 1 22846 25972
7 3C129 : 0003 1 0/09:07:05 - 0/09:12:25 1 25973 35132
8 0420+417 : 0003 B 1 0/09:17:05 - 0/09:18:45 1 35133 38213
9 3C129 : 0003 1 0/09:40:25 - 0/09:45:05 1 38214 47664
10 0420+417 : 0003 B 1 0/09:49:35 - 0/09:51:55 1 47665 52167
Source summary
Velocity type = ' ' Definition = ' '
ID Source Qual Calcode RA(1950.0) Dec(1950.0) IFlux QFlux UFlux VFlux No. vis
1 0134+329 : 0003 C 01:34:49.8320 32:54:20.520 0.000 0.000 0.000 0.000 36
IF( 2) 0.000 0.000 0.000 0.000
2 0420+417 : 0003 B 04:20:27.9370 41:43:08.045 0.000 0.000 0.000 0.000 16381
IF( 2) 0.000 0.000 0.000 0.000
3 0518+165 : 0003 C 05:18:16.5320 16:35:26.900 0.000 0.000 0.000 0.000 6288
IF( 2) 0.000 0.000 0.000 0.000
4 3C129 : 0003 04:45:31.6950 44:55:19.950 0.000 0.000 0.000 0.000 29462
IF( 2) 0.000 0.000 0.000 0.000
ID Source Freq(GHz) Velocity(Km/s) Rest freq (GHz)
1 All Sources 4.8851 0.0000 0.0000
IF( 2) 4.5851 0.0000 0.0000
Frequency Table summary
FQID IF# Freq(GHz) BW(kHz) Ch.Sep(kHz) Sideband
1 1 4.88510000 50000.0039 50000.0039 1
2 4.58510000 50000.0039 50000.0039 1
AIPS 1: Resumes
Get antenna positions
go prtan
Location Of VLA Antennas
N18 (26)
N16 ( 1)
N14 ( 9)
N12 (11)
N10 (15)
N8 (27)
N6 (25)
N4 (14)
N2 (13)
( 3) W2 E2 ( 4)
(12) W4 E4 (22)
(21) W6 E6 (16)
( 8) W8 E8 (17)
( 2) W10 E10 (24)
(10) W12 E12 ( 5)
(18) W14 E14 (23)
(28) W16 E16 ( 7)
(20) W18 E18 ( 6)
VLA:_OUT (19)
VPT:_OUT (29)
AIPS 1: Resumes
Flag some bad data. Just run the commands and think about this later.
task 'uvflg'
default
dohist 1
getn 13
antenna 0
basel 0
timer 0 0 0 0 0 4 8 0
stokes ' '
opcode 'flag'
reason 'bad scan'
outfgver 1
go
timer 0 8 18 0 0 8 30 0
go
antenna 0
timer 0 9 10 0 0 9 15 0
go
reason 'bad ant
antenna 4,0
timer 0
Check out some properties of the raw data
Plots
task 'uvplt'
source '0518+165',' '
calcode ' '
stokes 'half'
timer 0
uvrange 0
bif 0
eif 0
docalib 0
gainuse 1
bparm 0 1
do3col 1
dotv 1
tvinit
go
source '0420+417', ' '
tvinit
go
source '3C129', ' '
tvinit
go
bparm 6 7
source '0518+165',' '
tvinit
go
source '0420+417', ' '
tvinit
go
source '3C129', ' '
tvinit
go
bparm 0
Raw numbers
task 'listr'
optype 'list'
antenna 4,0
basel 0
sources ' '
calcode '*'
bif 0
eif 0
docalib 0
stokes ' '
dparm 0
go
Begin the calibration
Apply the flux densities for the known calibrators
task 'setjy'
default
getn 13
source '0518+165',' '
bif 0
eif 0
optype 'calc'
aparm(2) 2
go
vlb054> SETJY1: BIF = 1 EIF = 2 /Range of IFs vlb054> SETJY1: '0518+165 ' IF = 1 FLUX = 3.7742 (Jy calcd) vlb054> SETJY1: '0518+165 ' IF = 2 FLUX = 3.9464 (Jy calcd) vlb054> SETJY1: / Using (1995.2) VLA or Reynolds (1934-638) coefficients
bif 1
eif 1
optype ' '
zerosp 3.7742, 0.380, -0.153, 0.0
go
bif 2
eif 2
zerosp 3.9464, 0.397, -0.161, 0.0
go
bif 0
eif 0
zerosp 0
optype 'calc'
Run the calibration for 3C138
task 'calib'
default
getn 13
calsour '0518+165',' '
uvrange 0
antenna 0
refant 4
minamper 10
minphser 10
weightit 1
get2n 6
ncomp 0
solmode 'A&P'
aparm(6) 2
solint 2
solsub 2
cparm(3) 10
cparm(4) 10
go
clrmsg
Calibrate the phase calibrator
clr2n
calsour '0420+417', ' '
solint 0
uvrange 0
go
clrmsg
Check the results
task 'snplt'
antenna 0
stokes ' '
inext 'sn'
inver 1
sources ' '
timer 0
optype 'amp'
opcode 'alsi'
do3col 1
dotv 1
nplots 9
tvinit
go
optype 'phas'
go
inver 2
optype 'amp'
go
optype 'phas'
go
Use the amplitude calibrator to get the phase calibrator flux density
task 'getjy'
sources '0420+417', ' '
calsour '0518+165',' '
calcode ' '
bif 0
eif 0
antenna 0
timer 0
snver 0
go
vlb054> GETJY1: Task GETJY (release of 31DEC08) begins\\ vlb054> GETJY1: Source:Qual CALCODE IF Flux (Jy) vlb054> GETJY1: 0420+417 : 3 B 1 1.33893 +/- 0.00641 vlb054> GETJY1: 2 1.34714 +/- 0.00525 vlb054> GETJY1: Appears to have ended successfully vlb054> GETJY1: vlb054 31DEC08 TST: Cpu= 0.0 Real= 0
Redo the phase calibrator calibration
Now that we know the flux density of the phase calibrator, run through its calibration again, just to be sure AIPS doesn't have some information left around from calibrating before with an unknown flux density.
inext 'sn'
inver 2
extdest
inver 0
tget calib
go
clrmsg
Apply the calibration to all sources
task 'clcal'
sources '0518+165','0420+417', '3C129', ' '
calsour '0518+165','0420+417', ' '
opcode 'cali'
gainver 1
gainuse 2
refant 4
interp '2pt'
doblank 1
go
Check the results
Plots
task 'uvplt'
docalib 1
gainuse 2
source '0420+417', ' '
stokes 'half'
aparm 0
bparm 0 1
doweight 1
uvrange 0
tvinit
go
Now start the polarization calibration
Check the paralactic angles
task 'listr'
sources '0518+165','0420+417', ' '
inext 'cl'
inver 2
optype 'gain'
dparm 9,0
go
Make a backup of calibration information
task 'tasav'
clro
go
Run the polarization calibration on the phase calibrator
task 'pcal'
calsour '0420+417', ' '
timer 0
antenna 0
uvrange 0
bif 0
eif 0
docalib 1
gainuse 2
clr2n
pmodel 0
solint 3
soltype 'appr'
prtlev 1
refant 4
bparm 0
cparm 0
go
clrmsg
vlb054> PCAL 1: Calibration source 1 vlb054> PCAL 1: Q+iU=( 0.00444, -0.04706) +/- ( 0.000273, 0.000273) Jy vlb054> PCAL 1: Pol. inten. = 0.04727 +/- 0.000386 Jy, angle = -42.30 +/- vlb054> 0.165 deg vlb054> PCAL 1: 0420+417 I,Q,U,V = 1.3389 0.00444 -0.04706 0.00000 J vlb054> y vlb054> PCAL 1: Calibration source 1 vlb054> PCAL 1: Q+iU=( 0.02002, 0.03901) +/- ( 0.000277, 0.000277) Jy vlb054> PCAL 1: Pol. inten. = 0.04385 +/- 0.000392 Jy, angle = 31.42 +/- vlb054> 0.181 deg vlb054> PCAL 1: 0420+417 I,Q,U,V = 1.3471 0.02002 0.03901 0.00000 J vlb054> y
Check the phase difference between polarizations on a polarization calibrator
task 'rldif'
source '0518+165', ' '
timer 0
antenna 0
uvrange 0,45
docalib 1
gainuse 2
dopol true
go
outputs
AIPS 1: RLDIF: Task to return Right - Left phase difference AIPS 1: Adverbs Values Comments AIPS 1: ---------------------------------------------------------------- AIPS 1: CLCORPRM 132.6554 -74.984 R-L phase difference returned AIPS 1: *rest 0
Make backups again
task 'tasav'
clro
go
Find out what the polarization angle on the sky is supposed to be
Polarization data for C band from http://www.vla.nrao.edu/astro/calib/polar/1999/
Correct number is -21.71
Correct the measured values
for i=1 to 2;clcorp(i) = -21.71 - clcorp(i);end
Apply the corrections
task 'clcor'
source ' '
antenna 0
timer 0
bif 0
eif 0
gainver 2
gainuse 0
opcode 'polr'
stokes 'l'
go
Check that the angles are now correct
task 'rldif'
source '0518+165', ' '
timer 0
antenna 0
uvrange 0,45
docalib 1
gainuse 3
dopol true
go
outputs
AIPS 1: RLDIF: Task to return Right - Left phase difference AIPS 1: Adverbs Values Comments AIPS 1: ---------------------------------------------------------------- AIPS 1: CLCORPRM -21.71 -21.71 R-L phase difference returned AIPS 1: *rest 0
##########################
Work on just the target data now
Run SPLIT on the two datasets
task 'split'
getn 4
source '3C129', ' '
timer 0
bif 0
eif 0
docalib 1
gainuse 3
dopol true
stokes ' '
douvcomp false
aparm 0
go
getn 13
go
clrmsg
Check for where the new datafiles are stored
pcat
AIPS 1: Catalog on disk 1 AIPS 1: Cat Usid Mapname Class Seq Pt Last access Stat AIPS 1: 1 101 19940725 .C BAND. 1 UV 13-NOV-2008 17:24:12 AIPS 1: 2 101 19940725 .X BAND. 1 UV 13-NOV-2008 17:24:13 AIPS 1: 3 101 19940725 .X BAND. 2 UV 13-NOV-2008 17:24:13 AIPS 1: 4 101 19940725 .C BAND. 2 UV 13-NOV-2008 18:24:07 AIPS 1: 5 101 19940725 .U BAND. 1 UV 13-NOV-2008 17:24:13 AIPS 1: 6 101 3C138_C .MODEL . 1 MA 13-NOV-2008 17:51:33 AIPS 1: 7 101 3C48_C .MODEL . 1 MA 13-NOV-2008 16:19:09 AIPS 1: 8 101 19940725 .TASAV . 1 UV 13-NOV-2008 17:24:13 AIPS 1: 9 101 19940725 .TASAV . 2 UV 13-NOV-2008 17:24:13 AIPS 1: 10 101 19941103 .C BAND. 1 UV 13-NOV-2008 17:24:36 AIPS 1: 11 101 19941103 .X BAND. 1 UV 13-NOV-2008 17:24:36 AIPS 1: 12 101 19941103 .X BAND. 2 UV 13-NOV-2008 17:24:36 AIPS 1: 13 101 19941103 .C BAND. 2 UV 13-NOV-2008 18:24:18 AIPS 1: 14 101 19941103 .TASAV . 1 UV 13-NOV-2008 17:54:20 AIPS 1: 15 101 19941103 .TASAV . 2 UV 13-NOV-2008 17:56:30 AIPS 1: 16 101 3C129 .SPLIT . 1 UV 13-NOV-2008 18:24:07 AIPS 1: 17 101 3C129 .SPLIT . 2 UV 13-NOV-2008 18:24:18
Combine the two different observations into one big one
task 'dbcon'
getn 16
get2n 17
go
pcat
AIPS 1: 18 101 3C129 .DBCON . 1 UV 13-NOV-2008 18:28:31
Imaging
IMAGR is the standard imaging tool for AIPS
This will start up an imaging/cleaning session. Draw boxes and clean the source structure. Do this for all 4 Stokes parameters. (Unfortunately, IMAGR requires separate runs for the different Stokes parameters.)
task 'imagr'
getn 18
stokes 'i'
dopol 0
cellsize 0.25,0.25
imsize 2048,2048
clr2n
do3dimag 1
docalib 0
uvrange 0
niter 20000
overlap 1
go
clrmsg
stokes 'q'
go
clrmsg
stokes 'u'
go
clrmsg
stokes 'v'
go
clrmsg
Check where the files went
pcat
AIPS 1: 29 101 3C129 .IBM001. 3 MA 13-NOV-2008 19:46:00 AIPS 1: 30 101 3C129 .ICL001. 5 MA 13-NOV-2008 19:46:00 AIPS 1: 31 101 3C129 .QBM001. 1 MA 13-NOV-2008 19:47:30 AIPS 1: 32 101 3C129 .QCL001. 1 MA 13-NOV-2008 19:47:30 AIPS 1: 33 101 3C129 .UBM001. 1 MA 13-NOV-2008 19:49:06 AIPS 1: 34 101 3C129 .UCL001. 1 MA 13-NOV-2008 19:49:06 AIPS 1: 35 101 3C129 .VBM001. 1 MA 13-NOV-2008 19:49:39 AIPS 1: 36 101 3C129 .VCL001. 1 MA 13-NOV-2008 19:49:39
Polarization images
Combine Q and U to get linear polarization
task 'comb'
opcode 'polc'
getn 32
get2n 34
aparm 0
bparm(1) 28E-6
bparm(2) 28E-6
go
Get the linear polarization angle
opcode 'pola'
go
Check where file went
pcat
AIPS 1: 28 101 3C129 .PPOLC . 1 MA 13-NOV-2008 19:59:45 AIPS 1: 37 101 3C129 .PANG . 1 MA 13-NOV-2008 20:00:28
Look at the images
Linear Polarization
getn 28
tvinit
tvlod
tvfiddle
tvstat
AIPS 1: Mean= 1.3417E-05 rms= 2.8180E-05 JY/BEAM over 178694. pixels
Polarization Angle
getn 37
tvinit
tvlod
tvfiddle
I
getn 30
tvinit
tvlod
tvfiddle
tvstat
Clip the data so we only see information where there is good S/N
task 'comb'
getn 37
get2n 28
opcode 'clip'
aparm(1) 100E-6
aparm(10) 100E-6
bparm 0
outclass 'PANGC'
go
task 'comb'
getn 28
get2n 28
opcode 'clip'
aparm(1) 100E-6
aparm(10) 100E-6
bparm 0
outclass 'POLCC'
go
Check where these files went
pcat
AIPS 1: 38 101 3C129 .PANGC . 1 MA 13-NOV-2008 20:31:21 AIPS 1: 39 101 3C129 .POLCC . 1 MA 13-NOV-2008 20:31:21
Look at the polarization angle
getn 38
tvinit
tvlod
tvfiddle
Plotting your data
Plot I contours and P greyscale
task 'kntr'
getn 30
get2n 28
docont 1
dogrey 2
dovect 0
pixrange 0 1E-3
clev 28E-6
levs=-16,-8,8,16,32,64,128,256,512,1024
dowedge true
cbplot 1
dotv 1
blc 950 950
trc 1500 1500
go
Plot I contours and colors for polarization angle
task 'pcntr'
getn 30
get2n 32
get3n 34
docont 1
dogrey 2
dovect 1
pixrange 0 1E-3
clev 28E-6
levs=-16,-8,8,16,32,64,128,256,512,1024
factor 5
pol3col 1
pcut 80E-6
icut 0
dowedge 0
cbplot 1
dotv 1
blc 950 950
trc 1500 1500
go
Final Images
