Renaming a Field

↵ Hints, Tips, and Tricks

Sometimes sources are named the "wrong" thing in the original data set, and it would be nice to change the field name. Such as in this case I just encountered:

The flux calibrator in a data set was named "J1331+3030'. setjy only recognizes three names for this source ('3C286', '1328+307', and '1331+305')---none of which match the field name in the dataset. So, if we try to run setjy on this source, we'll see that the flux density is set to 1 Jy, which is incorrect.

2010-02-10 23:35:30 INFO setjy	##########################################
2010-02-10 23:35:30 INFO setjy	##### Begin Task: setjy              #####
2010-02-10 23:35:30 INFO  	setjy::::casa
2010-02-10 23:35:30 INFO setjy	  J1331+3030  spwid=  0  [I=1, Q=0, U=0, V=0] Jy, (default)
2010-02-10 23:35:30 INFO setjy	Selecting data
2010-02-10 23:35:30 INFO setjy	Selected 4818 out of 70290 visibilities.
2010-02-10 23:35:30 INFO setjy	Fourier transforming: replacing MODEL_DATA column
2010-02-10 23:35:30 INFO setjy	Processing after subtracting componentlist 
/export/home/rso-lchomiuk/test/Leo/leotest.ms.J1331+3030.spw0.tempcl
2010-02-10 23:35:30 INFO setjy	Performing interferometric gridding with convolution function SF
2010-02-10 23:35:31 INFO  	setjy::::casa
2010-02-10 23:35:31 INFO setjy	##### End Task: setjy                #####
2010-02-10 23:35:31 INFO setjy	##########################################

In order for setjy to work properly, we need to change the name of our flux calibrator. We can do this in two ways, the first using table utilities:

tb.open('leotest.ms/FIELD',nomodify=False)
st=tb.selectrows(4)
st.putcol('NAME','1331+305')
st.done()
tb.close()

The second is a bit more user-friendly, with the task browsetable:

#  browsetable :: Browse a table (MS, calibration table, image)
tablename           = 'leotest.ms'      #  Name of input table
async               =      False        #  If true the taskname must be started using browsetable(...)

This will bring up a GUI that looks like this:

Click on 'Table Keywords', one of the tabs at the screen's left. We'll then see a window that looks like this:

Double click on 'FIELD'. This will take us to a screen that looks like this:

Enter 'edit table' mode by clicking on the icon that looks like this: Double click on the cells that need editing (in this case, those that read 'J1331+3030') and type the corrected name.

We should be all set! Quit out of browsetable by going to the File Menu >> Exit. Double-check the edits using listobs.

And, if we run setjy again:

2010-02-11 00:31:42 INFO setjy	##########################################
2010-02-11 00:31:42 INFO setjy	##### Begin Task: setjy              #####
2010-02-11 00:31:42 INFO  	setjy::::casa
2010-02-11 00:31:42 INFO setjy	    1331+305  spwid=  0  [I=14.75, Q=0, U=0, V=0] Jy, (Perley-Taylor 99)
2010-02-11 00:31:42 INFO setjy	Selecting data
2010-02-11 00:31:42 INFO setjy	Selected 4818 out of 70290 visibilities.
2010-02-11 00:31:42 INFO setjy	Fourier transforming: replacing MODEL_DATA column
2010-02-11 00:31:42 INFO setjy	Processing after subtracting componentlist 
/export/home/rso-lchomiuk/test/Leo/leotest.ms.1331+305.spw0.tempcl
2010-02-11 00:31:42 INFO setjy	Performing interferometric gridding with convolution function SF
2010-02-11 00:31:43 INFO  	setjy::::casa
2010-02-11 00:31:43 INFO setjy	##### End Task: setjy                #####
2010-02-11 00:31:43 INFO setjy	##########################################

14.75 Jy...much better.

Last checked on CASA Version 3.0.0 (r9860).

--Laura Chomiuk 00:10, 11 February 2010 (UTC)