So from here we want to do the clean algorithm. At first we can have a look
how the field looks like at the moment in the residual map. So for that we
use the command mappl. And then we have an image on the right side. At
first starting image of at least something. And you see there is a center
bright spot as I said which we assume. And now we need to start to model that
thing. We know that the most flux is coming from the center. So what we can do
is to tell divmap only search for components in a certain area. This is
done by so-called clean windows. Those clean windows can be defined in the
mappl command. So where we are right now you just click left into the field and
then you already see there is a rectangular that is being opened. With
that you can draw a window and click a second time and then you see that the
window stays where it is. And now for divmap this means when clean components
are being searched for only search within this clean window. Now we want to
keep it as this is for now. We close the window with a right click and get back
to our terminal. Now we want to search for 100 clean components. So type clean
100 and we define them to be 0.03. With 0.03 we set the clean
components to be with a flux scale of the factor of 0.03 for all of the
components. Then we confirm and then there is a bunch of information. So it
gives us like the info the first 50 flux components were cleaned with a total
flux of 474 milli Jansky and after a hundred components we have cleaned
roughly 600 milli Jansky. It gives also here the total information for total
flux that was subtracted with the components which is roughly 600
milli Jansky as we have seen above already. And then there is also more
statistic information of the residual minimum, the mean, maximum, the root mean
square and well of course again the model that we have built for now how
much flux is contained in the model in the latest model. We can have a look at
the components where they have been placed. We can just type in MAPL again.
Then we see already that the image looks slightly different because there is no
flux removed from the image and you see now the residual image. So the initial
image that we had at the beginning minus the clean components and to see where
those components were modeled you click in the field of the of the map and then
type M for models and there you see there is a bunch of pluses in there. So
let's zoom in with Z and there you see there is a few pluses in there. The gray
scaling in the background is now the residual so you need to imagine to add
so you need to add the flux of those components to the whole image and then
you get to the initial image that we had before. So this image will change in the
procedure of the imaging. Before we continue to clean we need to self
calibrate our data set to the models that we already have established and
that we do by the selfcal command and confirm and there we see how our root
mean squares change before and after the selfcal and our sigmas. Now we want to
add even more components and improve our model. But because typing all of
that stuff is kind of tedious and we are a bit lazy we can do loopings. So
DIVMAP is able to accept loop commands so you can for once you can add multiple
commands one after another with a semicolon. So what we did before is clean
100 0.3 and afterwards we did the selfcal so let's do semicolon selfcal
and afterwards we showed them the residual map to us so semicolon mapple.
Now it will perform three commands one after the other and we put it in just
one line so hit confirm it does all of the things and we see that it already
opened the new window. So let's have a look at the new window type M again and
now we see something interesting. So there is not only green pluses in there
Presenters
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00:17:24 Min
Aufnahmedatum
2022-04-05
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2022-04-05 13:26:04
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