IRAS_10178-595 Black Body example
Fitting can also be done in AVO-ALadin VOSpec plugin
Process demonstrated in this sequence of plots from Pedro, described below
IRAS_10178-5958_1.png; IRAS_10178-5958_2.png; IRAS_10178-5958_3.png;
IRAS_10178-5958_4.png
From Pedro.Osuna <at> sciops.esa.int Tue Nov 16 22:25:13 2004
the Black Body fitting IS already available at the VOSpec usual place:
http://pma.standby.vilspa.esa.es:8080/vospec/index.html
I send a brief description of what we have done and how it should be used:
Rather than fitting two, three or N black bodies, we allow the
user to decide how many fittings he wants. To do a fitting, the user
selects a region on the spectrum, and then clicks on the Black Body
fitting to obtain it. Obviously, the user has to acknowledge somehow
the places of the spectrum that might possibly correspond to a black
body. For it, the units selection have to be done in lambda*F(lambda)
which we specify as W/m^2.
A very clear example of a well fitted black body is the
IRAS 10178-5958 that Pedro (Garcia) sent. To get the black bodies
for this object, execute the following steps:
1) Open the VOSpec at:
http://pma.standby.vilspa.esa.es:8080/vospec/index.html
2) Input IRAS 10178-5958 in the target search and 0.1 in the size
3) Click Go
4) Select ISO and IUE. HST does not contain any data.
5) Select all the results and click Display
6) Check the units "Log scale" and select the units W/m^2 for flux
7) There is a very clear black-body like curve at the rightmost part
of the spectrum (see figure IRAS_10178-5958_1). Select it (see
figure IRAS_10178-5958_2) and click "Fit"
8) Select Black Body and click Generate
9) The temperature will appear in the window, and the fitting will
appear in the overal spectrum. To see the fit directly in the
image, select the region with the mouse, and set the display of
the black body fitting to be, e.g., "dots" (see figure
IRAS_10178-5958_3)
10) Click "View all"
11) Another apparently good candidate is to the left of the
previously selected region. Select the region and perform the
same operation as before (see image IRAS_10178-5958_4)
This operation can be done with any number of black bodies and in
any observation. Of course, if there exists no black body fitting the
spectrum, the result will be meaningless, which is as expected.
The black body obtained can bee seen as just another spectrum
(selectable from the table below the display) so you can see the
fitting in an isolated way. Also, by double clicking on the
table entry for the black body fitting, a window appears with the
derived temperature.
In passing, the derived temperatures are pretty close to the
ones obtained by Pedro (Garcia) which shows that the tool is acting
as expected.
It would be nice if some of the scientists around could propose
other objects with good black body spectra that we could fit, to
see how much utility we can give to the tool.
With respect to other data like the IRAS, MSX and 2MASS for this
object, we are working on how to make them available for the
VOSpec, and will post you on this later. Anyway, the idea is to
have them in SSAP-like format as I have already said in the past.
But I believe this is an item that we still have to discuss.
Please play around with the Black Body fitting, and let us know if
you have any comment.
Bear in mind that BB fitting depends on many things, and only a first
estimate of it can be done using simple algorithms. After conversations
with Pedro (Garcia), this is what he was expecting (temperature
estimations) and therefore this simple BB fitting should be enough for
the Stellar case purposes. Nevertheless, extensions to more complex
algorithms using other parameters could be implemented.
</verbatin>
-- Main.AnitaRichards
<br />
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