Finding data 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: what
sort of data do exist for an astronomical sources? And how
do I find them and access 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 out what sort of astronomical
data are available for
a given object or position in the sky. There are various
possibilities:
- Use the Aladin
applet:
One would
follow these steps:
- 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, Catalogs, and Spectra
checkboxes and
SUBMIT (this might take a while). A list of all
VO-compliant image, catalogue, and spectra 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 dataset by simply clicking on
the
grey square close to it
- by pressing SUBMIT
the requested data are loaded in the main Aladin
panel; see the images and spectra threads for details. As
regards catalogues, entries which contain the target are selected, the
corresponding catalogues (within the search radius) are loaded, and
then their entries overlayed on any pre-existing image.
- This searches only VO-compliant
services. One can also search all entries in Vizier by
selecting
 . Selection can be restricted by
wavelength, mission, and keyword. This provides access also to all the
journal tables.
- Alternatively, one can use Datascope,
a service provided by the US National Virtual Observatory (NVO). DataScope
is a VO discovery agent and browser
that allows astronomers to discover information available on
a given source or location. DataScope links all simple catalog and
image resources known
to the Virtual Observatory registries. No spectra are provided.
- Finally, one can also use AstroScope,
a service provided by AstroGrid to perform dynamic discovery of data
available for further
processing via a VO interface. This service adds value and
interoperates with Datascope. Unlike Datascope, which is a Web service,
AstroScope is a Java application which can be downloaded to the user's
computer.
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