EVLA 6cmWideband Tutorial SN2010FZ
Overview
This article describes the calibration and imaging of a single-pointing 6cm EVLA wideband continuum dataset on the galaxy NGC2967 (UGC5180) which was the location of the supernova candidate SN2010FZ. No supernova was detected in this observation, but the galactic continuum emission from this face-on spiral is adequately imaged. The data were taken in RSRO mode, with 1024 MHz of bandwidth in each of two widely spaced basebands (comprised each of 8 128 MHz spectral windows), spanning 4.5 to 7.5 GHz. We will use wideband imaging techniques in this tutorial.
This is a more advanced tutorial, and if you are a relative novice (and particularly for EVLA continuum calibration and imaging), it is strongly recommended that you start with the EVLA Continuum Tutorial 3C391 before tackling this dataset. We will not include basic information on CASA processing in this tutorial.
CASA Versions
This tutorial was written for the CASA Version 3.2.1 (release r15198 26 May 2011).
Obtaining the Data
The scheduling block (SB) processed appears in the EVLA archive under program AS1015 as AS1015_sb1658169_1.55388.89474846065 and was run on 2010-07-11 from 21:28 to 22:28 UT (size 37.74GB).
For the purposes of this tutorial, we have provided the raw SDM data (as would be extracted from the archive) as well as measurement sets created by filling the data (with the importevla task) and upon time-averaging to 10s (after application of the online flags).
To start your tutorial, depending on which dataset you start with, proceed to:
- To start with the raw SDM data: Start with the section below titled "Importing your EVLA data from SDM". This is where you would start if you were reducing data from the archive.
- To start with the raw filled MS: Start with the section below titled "Application of Online Flags and Averaging your MS".
- To start with the flagged and averaged MS: Start with the section below titled "Examining and Flagging your Averaged MS".
Importing your EVLA data from SDM
For the purposes of this tutorial, we assume that the SDM is resident on disk, in this case at the location:
/lustre/smyers/AS1015/AS1015_sb1658169_1.55388.89474846065
Use the actual location of your data when you carry out the commands.
The listsdm task will print out a summary of the scans, fields, spectral windows, and antennas present in your SDM.
# In CASA
listsdm('/lustre/smyers/AS1015/AS1015_sb1658169_1.55388.89474846065')
In the logger you should see:
================================================================================
SDM File: /lustre/smyers/AS1015/AS1015_sb1658169_1.55388.89474846065
================================================================================
Observer: Dr. Alicia M. Soderberg
Facility: EVLA, D-configuration
Observed from 2010/07/11/21:28:28.41 to 2010/07/11/22:28:17.73 (UTC)
Total integration time = 3589.32 seconds (1.00 hours)
Scan listing:
Timerange (UTC) Scan FldID FieldName SpwIDs Intent(s)
21:28:28.41 - 21:29:27.40 1 0 J0925+0019 [0, 1] CALIBRATE_PHASE
21:29:27.40 - 21:30:57.16 2 0 J0925+0019 [0, 1] CALIBRATE_PHASE
21:30:57.16 - 21:32:26.91 3 0 J0925+0019 [0, 1] CALIBRATE_PHASE
21:32:26.91 - 21:33:56.67 4 0 J0925+0019 [0, 1] CALIBRATE_PHASE
21:33:56.67 - 21:34:56.50 5 0 J0925+0019 [0, 1] CALIBRATE_PHASE
21:34:56.50 - 21:35:56.34 6 0 J0925+0019 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] CALIBRATE_PHASE
21:35:56.34 - 21:37:26.09 7 0 J0925+0019 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] CALIBRATE_PHASE
21:37:26.09 - 21:38:25.93 8 0 J0925+0019 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] CALIBRATE_PHASE
21:38:25.93 - 21:39:55.68 9 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:39:55.68 - 21:41:25.44 10 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:41:25.44 - 21:42:55.19 11 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:42:55.19 - 21:44:24.94 12 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:44:24.94 - 21:45:54.70 13 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:45:54.70 - 21:47:24.45 14 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:47:24.45 - 21:47:54.37 15 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:47:54.37 - 21:49:24.12 16 0 J0925+0019 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] CALIBRATE_PHASE
21:49:24.12 - 21:50:53.88 17 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:50:53.88 - 21:52:23.63 18 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:52:23.63 - 21:53:53.39 19 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:53:53.39 - 21:55:23.14 20 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:55:23.14 - 21:56:52.89 21 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:56:52.89 - 21:58:22.65 22 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:58:22.65 - 21:58:52.57 23 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
21:58:52.57 - 22:00:22.32 24 0 J0925+0019 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] CALIBRATE_PHASE
22:00:22.32 - 22:01:52.07 25 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:01:52.07 - 22:03:21.83 26 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:03:21.83 - 22:04:51.58 27 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:04:51.58 - 22:06:21.34 28 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:06:21.34 - 22:07:51.09 29 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:07:51.09 - 22:09:20.85 30 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:09:20.85 - 22:09:50.76 31 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:09:50.76 - 22:11:20.52 32 0 J0925+0019 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] CALIBRATE_PHASE
22:11:20.52 - 22:12:50.27 33 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:12:50.27 - 22:14:20.02 34 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:14:20.02 - 22:15:49.78 35 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:15:49.78 - 22:17:19.53 36 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:17:19.53 - 22:18:49.29 37 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:18:49.29 - 22:20:19.04 38 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:20:19.04 - 22:20:48.96 39 1 SN2010FZ [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] OBSERVE_TARGET
22:20:48.96 - 22:22:18.71 40 0 J0925+0019 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] CALIBRATE_PHASE
22:22:18.71 - 22:23:48.47 41 2 3C286 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] CALIBRATE_BANDPASS CALIBRATE_AMPLI
22:23:48.47 - 22:25:18.22 42 2 3C286 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] CALIBRATE_BANDPASS CALIBRATE_AMPLI
22:25:18.22 - 22:26:47.98 43 2 3C286 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] CALIBRATE_BANDPASS CALIBRATE_AMPLI
22:26:47.98 - 22:28:17.73 44 2 3C286 [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17] CALIBRATE_BANDPASS CALIBRATE_AMPLI
Spectral window information:
SpwID #Chans Ch0(MHz) ChWidth(kHz) TotBW(MHz) Baseband
0 64 7686.0 2000.0 128.0 BB_4
1 64 7836.0 2000.0 128.0 BB_8
2 64 4488.0 2000.0 128.0 BB_4
3 64 4616.0 2000.0 128.0 BB_4
4 64 4744.0 2000.0 128.0 BB_4
5 64 4872.0 2000.0 128.0 BB_4
6 64 5000.0 2000.0 128.0 BB_4
7 64 5128.0 2000.0 128.0 BB_4
8 64 5256.0 2000.0 128.0 BB_4
9 64 5384.0 2000.0 128.0 BB_4
10 64 6488.0 2000.0 128.0 BB_8
11 64 6616.0 2000.0 128.0 BB_8
12 64 6744.0 2000.0 128.0 BB_8
13 64 6872.0 2000.0 128.0 BB_8
14 64 7000.0 2000.0 128.0 BB_8
15 64 7128.0 2000.0 128.0 BB_8
16 64 7256.0 2000.0 128.0 BB_8
17 64 7384.0 2000.0 128.0 BB_8
Field information:
FldID Code Name RA Dec SrcID
0 D J0925+0019 09:25:07.82 +000.19.13.933 0
1 NONE SN2010FZ 09:42:04.77 +000.19.51.000 1
2 K 3C286 13:31:08.29 +030.30.32.959 2
Antennas (27):
ID Name Station Diam.(m) Lat. Long.
0 ea01 W09 25.0 +000.00.00.0 +000.00.00.0
1 ea02 E02 25.0 +033.53.51.0 -107.37.25.2
2 ea03 E09 25.0 +033.54.01.1 -107.37.04.4
3 ea04 W01 25.0 +033.53.53.6 -107.36.45.1
4 ea05 W08 25.0 +033.54.00.5 -107.37.05.9
5 ea06 N06 25.0 +033.53.53.0 -107.37.21.6
6 ea08 N01 25.0 +033.54.10.3 -107.37.06.9
7 ea09 E06 25.0 +033.54.01.8 -107.37.06.0
8 ea10 N03 25.0 +033.53.57.7 -107.36.55.6
9 ea11 E04 25.0 +033.54.04.8 -107.37.06.3
10 ea12 E08 25.0 +033.53.59.7 -107.37.00.8
11 ea13 N07 25.0 +033.53.55.1 -107.36.48.9
12 ea14 E05 25.0 +033.54.12.9 -107.37.07.2
13 ea15 W06 25.0 +033.53.58.8 -107.36.58.4
14 ea16 W02 25.0 +033.53.56.4 -107.37.15.6
15 ea17 W07 25.0 +033.54.00.9 -107.37.07.5
16 ea18 N09 25.0 +033.53.54.8 -107.37.18.4
17 ea19 W04 25.0 +033.54.19.0 -107.37.07.8
18 ea20 N05 25.0 +033.53.59.1 -107.37.10.8
19 ea21 E01 25.0 +033.54.08.0 -107.37.06.7
20 ea22 N04 25.0 +033.53.59.2 -107.37.05.7
21 ea23 E07 25.0 +033.54.06.1 -107.37.06.5
22 ea24 W05 25.0 +033.53.56.5 -107.36.52.4
23 ea25 N02 25.0 +033.53.57.8 -107.37.13.0
24 ea26 W03 25.0 +033.54.03.5 -107.37.06.2
25 ea27 E03 25.0 +033.54.00.1 -107.37.08.9
26 ea28 N08 25.0 +033.54.00.5 -107.37.02.8
The C-band data of interest is contained in scans 6-44 and spans spectral windows 2 to 17.
We use the importevla task to convert the SDM dataset from the archive to a CASA Measurement Set (MS).
# In CASA
importevla(asdm='/lustre/smyers/AS1015/AS1015_sb1658169_1.55388.89474846065', \
vis='SN2010FZ_filled.ms',online=True,flagzero=True, \
shadow=True,applyflags=False,tbuff=1.5,flagbackup=False)
Here we had the task create (but not apply) the online flagging commands, plus flags for zero-clipping and shadowing. The timeranges for the online flags were extended by 1.5sec (the integration time was 1sec) to account for some timing mismatches present in the EVLA data at this time. These online flags indicated times where the antennas were not on source (e.g. slewing) or had other detectable faults. The created flagging commands will be stored in the FLAG_CMD MS table and can be applied later. Note that if you set applyflags=True here then after filling the task will go ahead and apply the flags for you.
For the purposes of this exercise, in order to save time and disk space, we have turned off the automatic creation of flag column backups by setting flagbackup=False. If we make a mistake and need to recover flags then we will have to rerun all previous commands. We recommend that for real data processing that you leave the default value flagbackup=True in this and subsequent tasks.
You now have a MS called SN2010FZ_filled.ms in your working area. This should be 37GB like the SDM.
Application of Online Flags and Averaging your MS
If you are starting from the filled MS, you can find this at the AOC at:
/lustre/smyers/AS1015/SN2010FZ_filled.ms
Again, use the actual location of this file for your system.
NOTE: the following step will not work in Version 3.2.1 (you will get a blank plot) but should in later versions). You can examine the commands stored in the FLAG_CMD table using flagcmd.
# In CASA
flagcmd(vis='SN2010FZ_filled.ms',flagmode='table',optype='plot')
This will bring up a matplotlib plotter. You can have it plot to a PNG file instead:
# In CASA
flagcmd(vis='SN2010FZ_filled.ms',flagmode='table',optype='plot',outfile='plotSN2010FZ_flagcmd.png')
To apply the flags also use flagcmd:
# In CASA
flagcmd(vis='SN2010FZ_filled.ms',flagmode='table',optype='apply',flagbackup=False)
This can take a while for our 37GB dataset. It took 20min on my workstation.
With the known bad data flagged, we can now split out the data we want and also average down in time to make a smaller MS. For D-configuration (max baselines 1km) we can safely average to 3s or even 10s to reduce dataset size:
# In CASA
split(vis='SN2010FZ_filled.ms',outputvis='SN2010FZ_filled10s.ms',datacolumn='data',timebin='10s')
This can also take a while for our 37GB dataset. It took 20min on my workstation.
You now have a MS called SN2010FZ_filled10s.ms in your working area. This should be 3.2GB in size.
Examining and Flagging your Averaged MS
If you are starting from the pre-flagged averaged split MS, you can find this at the AOC at:
/lustre/smyers/AS1015/SN2010FZ_filled10s.ms
We use listobs to summarize our new MS:
# In CASA
listobs('SN2010FZ_filled10s.ms')
Scan 6 is a dummy scan so we will use scans 7 to 44 when we process our data.
To plot up the antenna positions in the array:
# In CASA
plotants('SN2010FZ_filled10s.ms')
NOTE: if after this point or any other you get table locks, use clearstat to clear them:
# In CASA
clearstat
Now we examine the MS looking for bad data to flag. The useful spw are 2~17. To get an idea of the data layout, plot a single baseline/channel versus time. We will use plotms - this will bring up an interactive GUI that will display 2-D Y vs.X style line plots:
# In CASA
plotms(vis='SN2010FZ_filled10s.ms',field='',spw='2~17:31~31',antenna='ea01&ea02',correlation='RR,LL',xaxis='time',yaxis='amp')
Look for bad antennas by picking the last field and plotting baselines versus antenna ea01:
# In CASA
plotms(vis='SN2010FZ_filled10s.ms',field='2',spw='2~17:31~31',antenna='ea01',correlation='RR,LL',xaxis='antenna2',yaxis='amp')
You should be able to see that antenna 11 (= ea13) is bad (very low amplitude, it has no C-band receiver!) and that some of the spectral windows on 15 and 23 (ea17,ea25) are also on the low side. Boxing and using Locate will show that spw 10~17 are suspect for these antennas.
Now look at the bandpass for ea02 - it is in the inner core and a prospective reference antenna. Exclude ea13 using negation in the selection:
# In CASA
plotms(vis='SN2010FZ_filled10s.ms',field='2',spw='2~17',antenna='ea02;!ea13',correlation='RR,LL',xaxis='frequency',yaxis='amp')
There is clearly less data for spw 11, and use of Locate shows spw 11 data only for ea02,ea03,04,08,09,11,12. We will later delete this incomplete spw. Note also the very strong RFI spike at 6614MHz (spw 10 ch 63) with clear ringing contaminating both spw 10 and 11. There is also a tremendous roll-off in spw 10. We will drop these spectral window when we process the data.
We can also step through the baselines to our antenna using iteraxis - use the ">" button to step through:
# In CASA
plotms(vis='SN2010FZ_filled10s.ms',field='2',spw='2~17',antenna='ea02;!ea13',correlation='RR,LL',xaxis='frequency',yaxis='amp',iteraxis='baseline')
This will make it easier to isolate the bad antennas. Now plot the phases, iterating through baselines to ea02:
# In CASA
plotms(vis='SN2010FZ_filled10s.ms',field='2',spw='2~17',antenna='ea02;!ea13',correlation='RR,LL',xaxis='frequency',yaxis='phase',iteraxis='baseline')
