And now, in order to see what the actual Values
are of the region surrounding it, let's go to
Analysis and look at the Pixel
Table. If I drag that Pixel Table over to here,
you can see now that you get a little box which gives
you, along the top and left side of that box,
the actual image pixel numbers. And you can actually,
if you want, go back and forth by one pixel at a
time, to see what the intensity of the supernova is,
in this particular case, very close to the
center of the remnant. Lets see, how close it really
is to the center? We'll just grab one of these little
handles here and drag our region
out to make it bigger. Boy, it really does look pretty
close to being in the very center of this big blob in the sky.
But, there's some other stuff, like what's going on here?
That doesn't look like it's part of some kind of spherically symmetric object.
So, these are all things that we will explore in the future, and
this gives you at least some idea about what can be
done using DS9. To look at another
source, lets do the following. First, lets get rid of our Pixel Table.
And, lets also get rid of our Horizontal Graph,
and our Vertical Graph. Bring this back
down a little bit, and now lets load a different
Observation. What we're going to do here, is instead of
looking at Cas A, we're going to look at another supernova
remnant, called Tycho. And, we'll load Tycho
into our observation box, here.
And Color, we'll, I guess, leave at HE, and
Scale, well, let's see what it looks like. That looks pretty good.
Okay, now notice that there are these kind of like gaps in the data, over here.
And, that is actually a reflection of the chips
in the Chandra satellite, and the fact that these chips are located side by side,
and there are some parts of the sky then that fall between the chips.
So, sometimes you'll see these X types of patterns that really
don't mean anything as far as the actual X-ray source is concerned.
But, now, I want to show you something interesting.
Lets go back to Analysis, and now we're going to look at an Image Server.
This is a set of data that actually consists
of other types of optical or
radio images of the same area in the sky.
So, if for instance we scroll down to NRAO NVSS
and click on that. What we end up with is
another little window, and it will now allow us
to retrieve that part of the sky that corresponds
to the Alpha and Delta, or the position
coordinates of the Tycho supernova remnant.
So, if we click on Retrieve, you now see a little
box. That is the radio image of the exact same
part of the sky, as we see here on the left.
So, what I'm going to do here, we can do something even
neater than just displaying it. I'm going to click on this left frame,
which is our original X-ray image. And now, if I go to frames,
and scroll down to Match Frames,
and I click on WCS, which is World Coordinate System,
boom! Look at what happened to our radio image.
It got slightly larger, and it got slightly larger in exact proportion
to the size of the X-ray image. So, now, we are seeing
the exact same areas in the sky in, at exactly
the same magnification. Now, we can do something
that's even more interesting. And that is, if we go to
Edit and change our Pointer to a Crosshair, now we
have a set of Crosshairs that can link up the radio
image over here with the X-ray image over here.
And, we can lock the two together. So, if we go
to Frame> Lock> Crosshairs, now we can
cruise around one of those images, picking
out regions say, here in the X-rays, and
seeing exactly what corresponds to that part
of the image in X-rays, in the radio regime.
So, you can cruise around the entire area and select
out regions of the sky that might be of interest to you.
Now, one of the things you'll notice right
away here, is that this radio image looks blurry.
It's not really blurry, it's just the fact that radio waves
have much longer wavelengths than X-rays, and because of
this, it's just a fact of life that you don't get the same
types of resolution for your images.
Things don't look quite as good in some radio images,
as they might have look in some X-ray images.
But, radio astronomers have a lot of tricks up their sleeves, and they
can use interferometry to make these radio images
appear very, very pristine and accurate, indeed.