The ideal calibrator: a central point source in an otherwise empty sky

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The ideal calibrator: a central point source in an otherwise empty sky

Logged on 10/02/13 19:08:17

We're going to be using the sky model and Measurement Set from Simulations 101 again. This sky model contains a central point source with an intrinsic flux of about a Jansky, the sort of thing that makes an excellent phase calibrator.

Attached once again are the sky model and the MS.

First thing we need to do is make a note of the name of the central point source. If you load the sky model into Tigger and sort by the Stokes-I flux then we want to identify the source with I = 1.14 Jy. If you have a FITS image of this field left over from the previous run then loading this up shows that we have indeed selected the central source -- see the attached screen grab.

It's called 43_J1930M76, so scribble that down somewhere, or leave your Tigger window open, or if you're unlike me and have a functional memory then simply memorize it.

The next thing we're going to do is simulate the visibilities for a sky model consisting only of this source with no instrumental effects and no thermal noise.

Start the meqbrowser, connect to a server and load If you're coming here straight from the previous simulation exercise then Ctrl+1 in the browser should do that last step for you.

Set up the options as per the screengrab below, or by loading up the attached central-point-source-no-G.tdl.conf file. Note that none of the UV-plane components are activated, and the only image-plane component that we are interested in in the sky model. Specifically, we have put the name of the central source that we identified earlier in the 'Source subset' field.

Compile the script and when the run time options appear, write the visibilities to the CORRECTED_DATA column.

Once the simulation has completed, click the 'TDL Exec' button and make a clean image with some sensible parameters. We now have a reference 'ideal' image for comparison to what is to follow.

Note that we'll be overwriting the CORRECTED_DATA column in the next section and making an image of it. Since that process will overwrite the FITS file we just made if we apply the default file names, you might want to rename or duplicate the

file that just got created.

Data products



Screenshot-Tigger - sumss_dec-74_field.lsm.html.png


Screenshot-TDL Compile-time Options.png


Screenshot-TDL Jobs & Runtime Options.png (header)

data range:-0.000281018,1.14189
clip range:0.000834386,0.00306519