Finding images for a given source
The analysis tools described in this suite of recipes are still in a
development phase. As such, they are not intended to fully cover the
whole possible astronomical needs. Some of their functionalities may be still
at a prototype level, and not fully validated
This thread illustrates how to answer a typical VO question: do
images in
a given wavelength range exist for an astronomical source? If so, how
do I find them and display them?? We use Aladin to
answer this question and accomplish this task with just a few mouse
clicks.
Let's assume one is interested in finding images at all wavelengths for
a a given object. One would
follow these steps:
- launch the Aladin
applet
- click on Load. The Server Selector
panel appears. Select
- fill the target name (say, NGC 4151) and the search radius
(say, 14 arc-minutes) in the Target
and Radius widgets of the Server Selector,
respectively
- tick the Images checkbox and
SUBMIT (this might take a while). A list of all
VO-compliant image servers (i.e, servers which provide images following
VO standards) is shown,
which contain images of NGC 4151
- at this point, one can expand the various services by clicking on
one or more of the
symbols; for example, by clicking on the SDSS symbol one is presented with a list
of images, in various filters, part of the Sloan Digital Sky Survey
- one can then select one or more images by simply clicking on the
grey square close to it
- by pressing SUBMIT
the requested images are loaded in the main Aladin
panel; in our example, we have selected WENNS, POSS I, 2MASS, GB6, and
SDSS images; to display more than one image at the same time we have
selected the "multiview" button at the bottom left of the Aladin panel
- One can simultaneously zoom on all of the images by selecting
them all ('CTRL A'). We refer to the Aladin
manual for more information on this and other manipulation features.
- A few sources of are visibile close
to our target. If one wants to know their
identification, if there is one, one can
try and use the NASA/IPAC
Extragalactic
Database (NED). Click on
 in the Server selector panel. A new plane
will be uploaded in Aladin,
overlaying the NED
sources in the field-of-view. By moving the mouse over one of the red
symbols, the
source identification will appear in the bottom sub-panel. By moving
the mouse over one column, the parameter name (e.g., redshift) will
appear. Selecting with the cursor more than one symbol on an image will
provide a list of NED
sources in the sub-panel.
- For Galactic sources, select Start SIMBAD pointer:
automatical object discovery
from the Tools menu of the main Aladin
panel, and then click on a symbol. If the object is in SIMBAD his
identification will be displayed after a few seconds.
- The loaded images can then be saved to be analyzed with the tool
of choice.
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