Recent developments include links from Simbad and VizieR to images of the sky (Aladin), links to external data archive and services (IUE, HEASARC, NED), a new implementation of the resource discovery service AstroGlu. A tool to query and check the service profiles, and a XML formatting for data exchange will also be shown.
The Centre de Données astronomiques de Strasbourg (CDS) has been providing database services to the the astronomical community for more than 25 years (http://cdsweb.u-strasbg.fr).
Several databases and services are developped and maintained at CDS:
All these services are accessible through the CDS web interface, together with documentation, the Nomenclature Dictionary, Yellow Page services, bibliographic data, etc.
Another common characteristic of all these services is their interconnectivity, with the other CDS services, and also with remote services, weaving a web which allows, in a few mouse clicks, to navigate from the pixels of a galaxy to its bibliography and the corresponding full text or to its IUE spectra.
These different databases and the navigation possibilities among them are shown in action in the demos.
The Simbad database gathers data for more than 2,500,000 astronomical objects. It can be queried by identifiers, coordinates or different criteria based on the basic data (Figure 1).
For instance a query by coordinates brings up a page containing the list of corresponding objects. This set of objects can be plotted, and each object can be queried by itself, displaying all its data:
By a simple click, the user can also access an image of the current object, either through the Aladin previewer, or through the much more powerful Aladin Java Applet (see below).
The Aladin Java Applet is primarily an image displayer (Figure 2). Most of these images come from the Aladin server itself. It has also access to different catalogue sources, namely SIMBAD, NED (http://ned.ipac.caltech.edu) and especially VizieR with about 1300 catalogues with coordinates, including very large reference catalogues such as the USNO A2.0. Objects from these catalogues can be overlayed on the images for identification purposes, also across wavelengths. Several other tools allow to compute angular distances, to draw an outline of extended objects, which will automatically be redrawn with the right scale and rotation on another image, to add the user's own labels, and so on.
From the objects overlayed on an image, it is possible to access the original data in the catalogue or the database and observation logs may allow the loading of archive images, or access to the remote data archive.
The Aladin Java application will also be distributed as a standalone application, allowing the possibility of using the user's own images, provided their FITS header contains the World Coordinates System (WCS) entries, and of overlaying the user's own catalogue data on images provided they are TSV (Tab Separated Value) formatted.
The VizieR database allows to query any of its 2400 catalogues and to select objects according to criteria set on any field of the catalogue (Figure 3).
The first step consists in finding the right catalogue among all the available catalogues. Criteria like the catalogue number, author name, keyword, selection of wavelength or mission are available, or a selection facility based on a Kohonen map (Poinçot et al. 1998).
Once one or several catalogues are selected, VizieR displays a form allowing to set criteria on any common field in these catalogues. The final result is a set of rows extracted from the catalogues.
Several links to Simbad objects or remote archive (IUE, FIRST/VLA:
http://sundog.stsci.edu/) already exist. The description of every catalogue contains also many links, mainly to the basic papers describing the catalogue or other related catalogues, but also to external databases when relevant.
VizieR output comes in HTML or in TSV format with standardized description in well-formed XML.
Wenger, M., et al. 2000, A&AS, to be published
Bonnarel, F., et al. 2000, A&AS, to be published
Ochsenbein, F., et al. 2000, A&AS, to be published
Poinçot, P., et al. 1998, A&AS, 130, 183