This is an old revision of the document!
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 11,15,0
sources '0518+165','0134+329','0420+417','3C129',
xinc=10
go
bparm 11,16,0
go
xinc=1
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
<file>
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
</file>
task 'calrd'
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
<file>
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
</file>
==== Get images (and thus clean components) for the calibrators ====
eif 0
zerosp 0
optype 'calc'
source = '0134+329',' '
go
object '3c138'
band 'c'
go
object '3c48'
band 'c'
go
pcat
<file>
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
</file>
==== 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
<file>
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
</file>
==== 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
<file>
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
</file>
==== 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
<file>
Ampscalar average of matrix = -30.19( 0.081) sigma = 1.160
Ampscalar average of matrix = 33.93( 0.097) sigma = 1.389
</file>
outputs
<file>
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
</file>
==== 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
<file>
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
</file>
###############
===== 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
<file>
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
</file>
==== Makre sure we have the right one ====
getn 13
imhe
==== Get the scan information ====
task 'listr'
default
getn 13
optype 'scan'
doweight 1
go
<file>
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
</file>
==== Get antenna positions ====
go prtan
<file>
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
</file>
===== 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
<file>
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
</file>
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
<file>
vlb054> GETJY1: Task GETJY (release of 31DEC08) begins
inext 'sn'
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
</file>
==== 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.
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
<file>
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
</file>
==== 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
<file>
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
</file>
==== 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
<file>
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
</file>
##########################
===== 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
<file>
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
</file>
==== Combine the two different observations into one big one ====
task 'dbcon'
getn 16
get2n 17
go
pcat
<file>
AIPS 1: 18 101 3C129 .DBCON . 1 UV 13-NOV-2008 18:28:31
</file>
===== 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
<file>
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
</file>
===== 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
<file>
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
</file>
==== Look at the images ====
=== Linear Polarization ===
getn 28
tvinit
tvlod
tvfiddle
tvstat
<file>
AIPS 1: Mean= 1.3417E-05 rms= 2.8180E-05 JY/BEAM over 178694. pixels
</file>
=== 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
<file>
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
</file>
=== 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
