Topcat and SAMP

Your result tables can be shared with Virtual Observatory tools like Topcat using the SAMP protocol.

  • Start Topcat first.
  • Choose a (completed) job from the job list, click on it, then switch to the “SAMP” tab.
    Click the link “Register with a local SAMP Hub”. Now the web application tries to register with the so-called SAMP hub of Topcat. Due to security reasons this function may be blocked in your browser. In that case, enable it by following the instructions at the SAMP tab. After the script is allowed to connect, there will still be another dialogue popping up from the SAMP hub, asking you to authorize the connection. Choose “Yes”.
  • Now the available SAMP clients will be listed. Click “Send table to topcat”. This sends your result table directly to Topcat, where it now appears!

Topcat allows you to investigate the table values (Table Browser) and plot the results for a quick check.


Screenshot of the SAMP tab, after enabling the script and authorizing the connection.


Here’s an example for plotting the 50 most massive halos (at redshift 0) from three halo catalogues of the BolshoiP simulation, using Topcat’s version 4.1:

  1. Write following query into CosmoSim’s query interface:
    SELECT * FROM BolshoiP.BDMV WHERE snapnum=214 ORDER BY Mvir DESC LIMIT 50

    and submit it to the Short Queue by pressing the “Submit new SQL Query” button.

  2. Once the query is finished, navigate to the “Results table” tab. You should see a list of the 50 most massive halos from the BDMV-catalogue of the BolshoiP simulation, sorted by mass (Mvir column).
  3. Leave the web browser open and start Topcat. This can usually be done like this:
    java -jar topcat-full.jar

    on unix-like environments. Consult Topcat’s documentation for more details.

  4. Go back to CosmoSim and switch to the SAMP-tab of the query interface. Click on the link “Register with a local SAMP Hub”, authorize the connection and hit “Send table to topcat”.
  5. In Topcat, your table now appears in the “Table List”. Click on the cube-icon tp-icon-cube3dplot for 3D plots. A new Cube Plot window opens.
    In the “Position” tab (default) choose your table from the “Table” drop-down menu and choose following axes:

    • X: BolshoiP__BDMV__x
    • Y: BolshoiP__BDMV__y
    • Z: BolshoiP__BDMV__z

    You can see now the 3D distribution of the most massive BDMV-halos in the cosmological box!

  6. [only for Topcat version 4.1 and above:]
    To make things more interesting, click on the “Form” tab and choose the “Add size mark” icon. At “Coordinates – Size:” choose the BolshoiP__BDMV__Mvir-column.
    Now small spheres are drawn with their radius indicating the mass of each halo!
    Enhance the plot by choosing Shading Mode “transparent” instead of “flat”. Now the centers of each halo are visible again and overlapping halos can be identified more easily.
  7. Query the database to get the 50 most massive halos from the BDMW and FOF catalogues as well:
    • SELECT * FROM BolshoiP.BDMV WHERE snapnum=214 ORDER BY Mvir DESC LIMIT 50
    • SELECT * FROM BolshoiP.FOF WHERE snapnum=214 ORDER BY mass DESC LIMIT 50

    (Replace Mvir by mass for FOF catalogues.)

  8. Send these tables also to Topcat.
  9. In Topcat’s 3D plot window, click on the icon with many blue and red dots and a green plus tp-icon-addplot (“Add a new positional plot control to the stack”).
    Choose the BDMW-table, adjust x,y,z coordinates and size as before. Repeat for the FOF-table (but use “mass” for the “Size” of spheres).
  10. Make the shading types for these two data sets also transparent. Your plot should now look similar to the one below. It is nicely visible that most of these halos are found in each of the three halo catalogues. BDMW halos are generally a little bit smaller, since these halos are cut-off at a higher density threshold.


The 50 most amssive halos at redshift 0 from the BDMV (red), BDMW (blue) and FOF (green) catalogue.

The 50 most massive halos at redshift 0 from the BDMV (red), BDMW (blue) and FOF (green) catalogue.

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