VIALACTEA KnowledgeBase

VL KnowledgeBase Access with TOPCAT

The VIALACTEA Knowledge Base (VLKB) is a collection of scientific data, stored as relational databases, and web services. The scientific data inside VLKB are accessible through a Virtual Observatory enabled infrastructure through the TAP protocol and the interface is located at this URL:

For a more friendly access we suggest to use TOPCAT ( and its VO TAP query dialog.

How to use TOPCAT:

  • download TOPCAT tool from the Downloads section of the web page ( ;
  • launch the application;
  • to open the VO Table Access Protocol (TAP) Query click on the Query button in the toolbar (blue arrow);
  • a new window will pop up:

  • at the bottom of the window, in the Select TAP Service panel,
    type the URL into the TAP URL field,
    then click the Use Service button

  • an Authentication dialog will pop up. Fill it in with User and Password and proceed;
  • the tool will show the Use Service panel containing: Metadata, Service Capabilities and ADQL Text;
  • with the Examples button (blue arro w in the previous figure) it is possible to generate ADQL queries (see next figures);

  • when the query is ready click on Run Query, your table result will be loaded in a new TOPCAT window.
  • click on the table name in the list, et voila les data!

VL KnowledgeBase Access through TAP Protocol (for expert users)

A direct access to the VLKB, without using other VIALACTEA tools, is available through its TAP interface, which base URL is:

VL DataCube Access through FITS-DB (for expert users)

To obtain FITS datacube access it is posible to use services: search, cutout and merge. Results are returned in form of an XML file, then direct investigation of these datacubes may be done by accessing the URL via a web browser or command line tool capable of HTTP connections (like, e.g., curl). These services were not designed to be handled interactively by the user, but rather by scripting tools, or programming languages.

For example to perform a search in the sky circular area of radius 0.1 centered at galactic coordinates [l,b] = [10,0] one would type into the browser:

The typical URL pattern of those services uses the requested <function> and related parameters list <paramlist>:<function>?<param>[&<paramlist>...]

The available services are: vlkb_search, vlkb_cutout and vlkb_merge.
The available query parameters in key=value pairs are described in table:

WARNING: - Currently you need authorization credentials to access all of the above services!

References :